BranchFolding.cpp revision 882d5217189a0656a231285ff7aef8e5e42bd687
1afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg//===-- BranchFolding.cpp - Fold machine code branch instructions ---------===// 2afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// 3001a3012ac66c279ba8076a13c59d71d025f2ed9Brian Paul// The LLVM Compiler Infrastructure 4afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// 5001a3012ac66c279ba8076a13c59d71d025f2ed9Brian Paul// This file is distributed under the University of Illinois Open Source 6afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// License. See LICENSE.TXT for details. 7afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// 8afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg//===----------------------------------------------------------------------===// 9afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// 10afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// This pass forwards branches to unconditional branches to make them branch 11afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// directly to the target block. This pass often results in dead MBB's, which 12afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// it then removes. 13afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// 14afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// Note that this pass must be run after register allocation, it cannot handle 15afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// SSA form. 16afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// 17afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg//===----------------------------------------------------------------------===// 18afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 19afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#define DEBUG_TYPE "branchfolding" 20afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/CodeGen/Passes.h" 21afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/CodeGen/MachineModuleInfo.h" 22afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/CodeGen/MachineFunctionPass.h" 23afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/CodeGen/MachineJumpTableInfo.h" 24afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/CodeGen/RegisterScavenging.h" 25afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/Target/TargetInstrInfo.h" 26e23e2759fc67973c0d2e3318f79837f88f8bad0dBrian Paul#include "llvm/Target/TargetMachine.h" 27e23e2759fc67973c0d2e3318f79837f88f8bad0dBrian Paul#include "llvm/Target/TargetRegisterInfo.h" 28afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/Support/CommandLine.h" 29afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/Support/Debug.h" 30afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/ADT/SmallSet.h" 31afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/ADT/Statistic.h" 32afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include "llvm/ADT/STLExtras.h" 33afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg#include <algorithm> 3408f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paulusing namespace llvm; 3508f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paul 3608f0374bfaccc41a497f18a6535fa0d13277abdeBrian PaulSTATISTIC(NumDeadBlocks, "Number of dead blocks removed"); 37afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgSTATISTIC(NumBranchOpts, "Number of branches optimized"); 38afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgSTATISTIC(NumTailMerge , "Number of block tails merged"); 39afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgstatic cl::opt<cl::boolOrDefault> FlagEnableTailMerge("enable-tail-merge", 40afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg cl::init(cl::BOU_UNSET), cl::Hidden); 41afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// Throttle for huge numbers of predecessors (compile speed problems) 42afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgstatic cl::opt<unsigned> 43afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgTailMergeThreshold("tail-merge-threshold", 44afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg cl::desc("Max number of predecessors to consider tail merging"), 452743def830bc1dc3bedb302f13db3d65dc4705d7Brian Paul cl::init(150), cl::Hidden); 4608f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paul 47afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgnamespace { 48afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg struct VISIBILITY_HIDDEN BranchFolder : public MachineFunctionPass { 492743def830bc1dc3bedb302f13db3d65dc4705d7Brian Paul static char ID; 50ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul explicit BranchFolder(bool defaultEnableTailMerge) : 51ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul MachineFunctionPass(&ID) { 52ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul switch (FlagEnableTailMerge) { 53ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break; 54ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul case cl::BOU_TRUE: EnableTailMerge = true; break; 55ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul case cl::BOU_FALSE: EnableTailMerge = false; break; 56ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul } 57ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul } 58afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 59afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg virtual bool runOnMachineFunction(MachineFunction &MF); 60ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul virtual const char *getPassName() const { return "Control Flow Optimizer"; } 61ae773f612c0b9262e9cf9fb63423a44d2125ce46Brian Paul const TargetInstrInfo *TII; 628da58f31846bd119070af78fac340a3e5da4f056Brian Paul MachineModuleInfo *MMI; 63afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool MadeChange; 64473e51f2fbfb003717bb88616ea585fc8d76f75eBrian Paul private: 65473e51f2fbfb003717bb88616ea585fc8d76f75eBrian Paul // Tail Merging. 66473e51f2fbfb003717bb88616ea585fc8d76f75eBrian Paul bool EnableTailMerge; 67473e51f2fbfb003717bb88616ea585fc8d76f75eBrian Paul bool TailMergeBlocks(MachineFunction &MF); 683e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz bool TryMergeBlocks(MachineBasicBlock* SuccBB, 693e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz MachineBasicBlock* PredBB); 703e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz void ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst, 713e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz MachineBasicBlock *NewDest); 723e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz MachineBasicBlock *SplitMBBAt(MachineBasicBlock &CurMBB, 733e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz MachineBasicBlock::iterator BBI1); 743e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz unsigned ComputeSameTails(unsigned CurHash, unsigned minCommonTailLength); 753e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz void RemoveBlocksWithHash(unsigned CurHash, MachineBasicBlock* SuccBB, 763e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz MachineBasicBlock* PredBB); 773e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz unsigned CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB, 783e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz unsigned maxCommonTailLength); 793e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz 803e2fa3fd5cafdc641138844276c4260e028684acKarl Schultz typedef std::pair<unsigned,MachineBasicBlock*> MergePotentialsElt; 812743def830bc1dc3bedb302f13db3d65dc4705d7Brian Paul typedef std::vector<MergePotentialsElt>::iterator MPIterator; 826799ecb6753f2ec5b1b66c9e8c447bc82035f94cTed Jump std::vector<MergePotentialsElt> MergePotentials; 83afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 84afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg typedef std::pair<MPIterator, MachineBasicBlock::iterator> SameTailElt; 8508f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paul std::vector<SameTailElt> SameTails; 8608f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paul 87afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg const TargetRegisterInfo *RegInfo; 88391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul RegScavenger *RS; 89391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul // Branch optzn. 90391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul bool OptimizeBranches(MachineFunction &MF); 91391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul void OptimizeBlock(MachineBasicBlock *MBB); 92391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul void RemoveDeadBlock(MachineBasicBlock *MBB); 93391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul bool OptimizeImpDefsBlock(MachineBasicBlock *MBB); 94391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul 95391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul bool CanFallThrough(MachineBasicBlock *CurBB); 96391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul bool CanFallThrough(MachineBasicBlock *CurBB, bool BranchUnAnalyzable, 97473e51f2fbfb003717bb88616ea585fc8d76f75eBrian Paul MachineBasicBlock *TBB, MachineBasicBlock *FBB, 98391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul const SmallVectorImpl<MachineOperand> &Cond); 99391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul }; 100473e51f2fbfb003717bb88616ea585fc8d76f75eBrian Paul char BranchFolder::ID = 0; 10108f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paul} 10208f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paul 10308f0374bfaccc41a497f18a6535fa0d13277abdeBrian PaulFunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) { 10408f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paul return new BranchFolder(DefaultEnableTailMerge); } 105afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 106afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// RemoveDeadBlock - Remove the specified dead machine basic block from the 10708f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paul/// function, updating the CFG. 10808f0374bfaccc41a497f18a6535fa0d13277abdeBrian Paulvoid BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) { 109afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg assert(MBB->pred_empty() && "MBB must be dead!"); 110afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg DOUT << "\nRemoving MBB: " << *MBB; 111afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 112afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineFunction *MF = MBB->getParent(); 113afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // drop all successors. 114391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul while (!MBB->succ_empty()) 115391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul MBB->removeSuccessor(MBB->succ_end()-1); 116391876e5e6a710ba99b0752bbcc1b3b8af0469b6Brian Paul 117afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If there are any labels in the basic block, unregister them from 118fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // MachineModuleInfo. 119afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MMI && !MBB->empty()) { 120fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); 121afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg I != E; ++I) { 122fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (I->isLabel()) 123fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // The label ID # is always operand #0, an immediate. 124fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MMI->InvalidateLabel(I->getOperand(0).getImm()); 125fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 126fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 127fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 128fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Remove the block. 129fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MF->erase(MBB); 130fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 131fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 132fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// OptimizeImpDefsBlock - If a basic block is just a bunch of implicit_def 133fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// followed by terminators, and if the implicitly defined registers are not 134fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// used by the terminators, remove those implicit_def's. e.g. 135fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// BB1: 136fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// r0 = implicit_def 137afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// r1 = implicit_def 138fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// br 139fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// This block can be optimized away later if the implicit instructions are 140fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// removed. 141fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulbool BranchFolder::OptimizeImpDefsBlock(MachineBasicBlock *MBB) { 142afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg SmallSet<unsigned, 4> ImpDefRegs; 143afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock::iterator I = MBB->begin(); 144fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul while (I != MBB->end()) { 145fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (I->getOpcode() != TargetInstrInfo::IMPLICIT_DEF) 146fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 147fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned Reg = I->getOperand(0).getReg(); 148fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ImpDefRegs.insert(Reg); 149fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (const unsigned *SubRegs = RegInfo->getSubRegisters(Reg); 150fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned SubReg = *SubRegs; ++SubRegs) 151fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ImpDefRegs.insert(SubReg); 152fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ++I; 153fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 154fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (ImpDefRegs.empty()) 155fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return false; 156fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 157fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock::iterator FirstTerm = I; 158fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul while (I != MBB->end()) { 159fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!TII->isUnpredicatedTerminator(I)) 160fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return false; 161fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // See if it uses any of the implicitly defined registers. 162fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { 163fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineOperand &MO = I->getOperand(i); 164fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!MO.isReg() || !MO.isUse()) 165fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul continue; 166fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned Reg = MO.getReg(); 167fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (ImpDefRegs.count(Reg)) 168fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return false; 169fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 170fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ++I; 171fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 172fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 173fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul I = MBB->begin(); 174fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul while (I != FirstTerm) { 175fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineInstr *ImpDefMI = &*I; 176fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ++I; 177fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MBB->erase(ImpDefMI); 178fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 179fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 180fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return true; 181fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 182fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 183fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulbool BranchFolder::runOnMachineFunction(MachineFunction &MF) { 184fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul TII = MF.getTarget().getInstrInfo(); 185fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!TII) return false; 186fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 187fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul RegInfo = MF.getTarget().getRegisterInfo(); 188fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 189fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Fix CFG. The later algorithms expect it to be right. 190fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul bool EverMadeChange = false; 191fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; I++) { 192fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *MBB = I, *TBB = 0, *FBB = 0; 193fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SmallVector<MachineOperand, 4> Cond; 194fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!TII->AnalyzeBranch(*MBB, TBB, FBB, Cond)) 195fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul EverMadeChange |= MBB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty()); 196fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul EverMadeChange |= OptimizeImpDefsBlock(MBB); 197fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 198fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 199fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul RS = RegInfo->requiresRegisterScavenging(MF) ? new RegScavenger() : NULL; 200fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 201fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MMI = getAnalysisToUpdate<MachineModuleInfo>(); 202fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 203fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul bool MadeChangeThisIteration = true; 204fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul while (MadeChangeThisIteration) { 205fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MadeChangeThisIteration = false; 206fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MadeChangeThisIteration |= TailMergeBlocks(MF); 207fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MadeChangeThisIteration |= OptimizeBranches(MF); 208fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul EverMadeChange |= MadeChangeThisIteration; 209fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 210fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 211fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // See if any jump tables have become mergable or dead as the code generator 212fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // did its thing. 213fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineJumpTableInfo *JTI = MF.getJumpTableInfo(); 214fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul const std::vector<MachineJumpTableEntry> &JTs = JTI->getJumpTables(); 215fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!JTs.empty()) { 216fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Figure out how these jump tables should be merged. 217fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul std::vector<unsigned> JTMapping; 218fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul JTMapping.reserve(JTs.size()); 219fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 220fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // We always keep the 0th jump table. 221fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul JTMapping.push_back(0); 222fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 223fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Scan the jump tables, seeing if there are any duplicates. Note that this 224fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // is N^2, which should be fixed someday. 225fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (unsigned i = 1, e = JTs.size(); i != e; ++i) 226fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul JTMapping.push_back(JTI->getJumpTableIndex(JTs[i].MBBs)); 227fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 228fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // If a jump table was merge with another one, walk the function rewriting 229fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // references to jump tables to reference the new JT ID's. Keep track of 230fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // whether we see a jump table idx, if not, we can delete the JT. 231fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul BitVector JTIsLive(JTs.size()); 232fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); 233fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul BB != E; ++BB) { 234fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end(); 235fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul I != E; ++I) 236fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) { 237fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineOperand &Op = I->getOperand(op); 238fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!Op.isJTI()) continue; 239fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned NewIdx = JTMapping[Op.getIndex()]; 240fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul Op.setIndex(NewIdx); 241fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 242fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Remember that this JT is live. 243fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul JTIsLive.set(NewIdx); 244fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 245fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 246fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 247fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Finally, remove dead jump tables. This happens either because the 248fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // indirect jump was unreachable (and thus deleted) or because the jump 249fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // table was merged with some other one. 250fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (unsigned i = 0, e = JTIsLive.size(); i != e; ++i) 251fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!JTIsLive.test(i)) { 252fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul JTI->RemoveJumpTable(i); 253fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul EverMadeChange = true; 254fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 255fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 256fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 257fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul delete RS; 258fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return EverMadeChange; 259fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 260fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 261fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul//===----------------------------------------------------------------------===// 262fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// Tail Merging of Blocks 263fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul//===----------------------------------------------------------------------===// 264fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 265fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// HashMachineInstr - Compute a hash value for MI and its operands. 266fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulstatic unsigned HashMachineInstr(const MachineInstr *MI) { 2670056c5e40d7c5702420f314fa4f68159e5a64cd6Brian Paul unsigned Hash = MI->getOpcode(); 268fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 269fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul const MachineOperand &Op = MI->getOperand(i); 270fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 2710056c5e40d7c5702420f314fa4f68159e5a64cd6Brian Paul // Merge in bits from the operand if easy. 272fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned OperandHash = 0; 273fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul switch (Op.getType()) { 274fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul case MachineOperand::MO_Register: OperandHash = Op.getReg(); break; 275fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul case MachineOperand::MO_Immediate: OperandHash = Op.getImm(); break; 276fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul case MachineOperand::MO_MachineBasicBlock: 277fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul OperandHash = Op.getMBB()->getNumber(); 278fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 279fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul case MachineOperand::MO_FrameIndex: 280fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul case MachineOperand::MO_ConstantPoolIndex: 281fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul case MachineOperand::MO_JumpTableIndex: 282fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul OperandHash = Op.getIndex(); 283fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 284fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul case MachineOperand::MO_GlobalAddress: 285fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul case MachineOperand::MO_ExternalSymbol: 286fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Global address / external symbol are too hard, don't bother, but do 287fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // pull in the offset. 288fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul OperandHash = Op.getOffset(); 289fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 290fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul default: break; 291fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 292fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 293fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul Hash += ((OperandHash << 3) | Op.getType()) << (i&31); 294fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 295fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return Hash; 296fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 297fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 298fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// HashEndOfMBB - Hash the last few instructions in the MBB. For blocks 299fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// with no successors, we hash two instructions, because cross-jumping 300fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// only saves code when at least two instructions are removed (since a 301fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// branch must be inserted). For blocks with a successor, one of the 302fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// two blocks to be tail-merged will end with a branch already, so 303fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// it gains to cross-jump even for one instruction. 304fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 305fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulstatic unsigned HashEndOfMBB(const MachineBasicBlock *MBB, 306fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned minCommonTailLength) { 307fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock::const_iterator I = MBB->end(); 308fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (I == MBB->begin()) 309fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return 0; // Empty MBB. 310fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 311fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul --I; 312fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned Hash = HashMachineInstr(I); 313fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 314fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (I == MBB->begin() || minCommonTailLength == 1) 315fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return Hash; // Single instr MBB. 316fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 317fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul --I; 318fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Hash in the second-to-last instruction. 319fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul Hash ^= HashMachineInstr(I) << 2; 320fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return Hash; 321fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 322fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 323fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// ComputeCommonTailLength - Given two machine basic blocks, compute the number 324fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// of instructions they actually have in common together at their end. Return 325fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// iterators for the first shared instruction in each block. 326fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulstatic unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1, 327fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *MBB2, 328fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock::iterator &I1, 329fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock::iterator &I2) { 330fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul I1 = MBB1->end(); 331fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul I2 = MBB2->end(); 332fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 333fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned TailLen = 0; 334fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul while (I1 != MBB1->begin() && I2 != MBB2->begin()) { 335fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul --I1; --I2; 336fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!I1->isIdenticalTo(I2) || 337fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // FIXME: This check is dubious. It's used to get around a problem where 338fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // people incorrectly expect inline asm directives to remain in the same 339fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // relative order. This is untenable because normal compiler 340fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // optimizations (like this one) may reorder and/or merge these 341fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // directives. 342fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul I1->getOpcode() == TargetInstrInfo::INLINEASM) { 343fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ++I1; ++I2; 344fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 345fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 346fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ++TailLen; 347fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 348fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return TailLen; 349fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 350fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 351fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// ReplaceTailWithBranchTo - Delete the instruction OldInst and everything 352fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// after it, replacing it with an unconditional branch to NewDest. This 353fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// returns true if OldInst's block is modified, false if NewDest is modified. 354df4fd765d5244cc09f18f6b0371909e7bf13be87Brian Paulvoid BranchFolder::ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst, 355df4fd765d5244cc09f18f6b0371909e7bf13be87Brian Paul MachineBasicBlock *NewDest) { 356fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *OldBB = OldInst->getParent(); 357fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 358fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Remove all the old successors of OldBB from the CFG. 359fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul while (!OldBB->succ_empty()) 360fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul OldBB->removeSuccessor(OldBB->succ_begin()); 361fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 362fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Remove all the dead instructions from the end of OldBB. 363fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul OldBB->erase(OldInst, OldBB->end()); 364fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 365fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // If OldBB isn't immediately before OldBB, insert a branch to it. 366fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (++MachineFunction::iterator(OldBB) != MachineFunction::iterator(NewDest)) 367fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul TII->InsertBranch(*OldBB, NewDest, 0, SmallVector<MachineOperand, 0>()); 368fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul OldBB->addSuccessor(NewDest); 369fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ++NumTailMerge; 370fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 371fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 372fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// SplitMBBAt - Given a machine basic block and an iterator into it, split the 373fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// MBB so that the part before the iterator falls into the part starting at the 374fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// iterator. This returns the new MBB. 375fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian PaulMachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB, 376fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock::iterator BBI1) { 377fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineFunction &MF = *CurMBB.getParent(); 378fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 379fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Create the fall-through block. 380fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineFunction::iterator MBBI = &CurMBB; 381fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *NewMBB =MF.CreateMachineBasicBlock(CurMBB.getBasicBlock()); 382fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul CurMBB.getParent()->insert(++MBBI, NewMBB); 383fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 384fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Move all the successors of this block to the specified block. 385fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul NewMBB->transferSuccessors(&CurMBB); 386fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 387fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Add an edge from CurMBB to NewMBB for the fall-through. 388fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul CurMBB.addSuccessor(NewMBB); 389fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 390fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Splice the code over. 391fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end()); 392fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 393fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // For targets that use the register scavenger, we must maintain LiveIns. 394fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (RS) { 395fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul RS->enterBasicBlock(&CurMBB); 396fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!CurMBB.empty()) 397fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul RS->forward(prior(CurMBB.end())); 398fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul BitVector RegsLiveAtExit(RegInfo->getNumRegs()); 399fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul RS->getRegsUsed(RegsLiveAtExit, false); 400fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (unsigned int i=0, e=RegInfo->getNumRegs(); i!=e; i++) 401fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (RegsLiveAtExit[i]) 402fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul NewMBB->addLiveIn(i); 403fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 404fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 405fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return NewMBB; 406fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 407fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 408fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// EstimateRuntime - Make a rough estimate for how long it will take to run 409fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// the specified code. 410fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulstatic unsigned EstimateRuntime(MachineBasicBlock::iterator I, 411fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock::iterator E) { 412fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned Time = 0; 413fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (; I != E; ++I) { 414fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul const TargetInstrDesc &TID = I->getDesc(); 415fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (TID.isCall()) 416fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul Time += 10; 417fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul else if (TID.mayLoad() || TID.mayStore()) 418fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul Time += 2; 419fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul else 420fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ++Time; 421fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 422fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return Time; 423fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 424fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 425fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// CurMBB needs to add an unconditional branch to SuccMBB (we removed these 426fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// branches temporarily for tail merging). In the case where CurMBB ends 427fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// with a conditional branch to the next block, optimize by reversing the 428fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// test and conditionally branching to SuccMBB instead. 429fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 430fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulstatic void FixTail(MachineBasicBlock* CurMBB, MachineBasicBlock *SuccBB, 431fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul const TargetInstrInfo *TII) { 432fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineFunction *MF = CurMBB->getParent(); 433fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineFunction::iterator I = next(MachineFunction::iterator(CurMBB)); 434fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *TBB = 0, *FBB = 0; 435fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SmallVector<MachineOperand, 4> Cond; 436fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (I != MF->end() && 437fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul !TII->AnalyzeBranch(*CurMBB, TBB, FBB, Cond)) { 438fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *NextBB = I; 439fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (TBB == NextBB && !Cond.empty() && !FBB) { 440fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!TII->ReverseBranchCondition(Cond)) { 441fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul TII->RemoveBranch(*CurMBB); 442fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul TII->InsertBranch(*CurMBB, SuccBB, NULL, Cond); 443fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return; 444fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 445fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 446fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 447fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul TII->InsertBranch(*CurMBB, SuccBB, NULL, SmallVector<MachineOperand, 0>()); 448fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 449fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 450fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulstatic bool MergeCompare(const std::pair<unsigned,MachineBasicBlock*> &p, 451fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul const std::pair<unsigned,MachineBasicBlock*> &q) { 452fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (p.first < q.first) 453fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return true; 454fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul else if (p.first > q.first) 455fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return false; 456fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul else if (p.second->getNumber() < q.second->getNumber()) 457fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return true; 458fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul else if (p.second->getNumber() > q.second->getNumber()) 459fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return false; 460fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul else { 461fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // _GLIBCXX_DEBUG checks strict weak ordering, which involves comparing 462fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // an object with itself. 463fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul#ifndef _GLIBCXX_DEBUG 464fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul assert(0 && "Predecessor appears twice"); 465fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul#endif 466fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return(false); 467fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 468fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 469fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 470fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// ComputeSameTails - Look through all the blocks in MergePotentials that have 471fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// hash CurHash (guaranteed to match the last element). Build the vector 472fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// SameTails of all those that have the (same) largest number of instructions 473fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// in common of any pair of these blocks. SameTails entries contain an 474fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// iterator into MergePotentials (from which the MachineBasicBlock can be 475fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// found) and a MachineBasicBlock::iterator into that MBB indicating the 476fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// instruction where the matching code sequence begins. 477fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// Order of elements in SameTails is the reverse of the order in which 478fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// those blocks appear in MergePotentials (where they are not necessarily 479fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// consecutive). 480fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulunsigned BranchFolder::ComputeSameTails(unsigned CurHash, 481fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned minCommonTailLength) { 482fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned maxCommonTailLength = 0U; 483fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SameTails.clear(); 484fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock::iterator TrialBBI1, TrialBBI2; 485fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MPIterator HighestMPIter = prior(MergePotentials.end()); 486fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (MPIterator CurMPIter = prior(MergePotentials.end()), 487fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul B = MergePotentials.begin(); 488fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul CurMPIter!=B && CurMPIter->first==CurHash; 489fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul --CurMPIter) { 490fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (MPIterator I = prior(CurMPIter); I->first==CurHash ; --I) { 491fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned CommonTailLen = ComputeCommonTailLength( 492fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul CurMPIter->second, 493fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul I->second, 494fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul TrialBBI1, TrialBBI2); 495fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // If we will have to split a block, there should be at least 496fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // minCommonTailLength instructions in common; if not, at worst 497fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // we will be replacing a fallthrough into the common tail with a 498fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // branch, which at worst breaks even with falling through into 499fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // the duplicated common tail, so 1 instruction in common is enough. 500fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // We will always pick a block we do not have to split as the common 501fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // tail if there is one. 502fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // (Empty blocks will get forwarded and need not be considered.) 503fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (CommonTailLen >= minCommonTailLength || 504fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul (CommonTailLen > 0 && 505fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul (TrialBBI1==CurMPIter->second->begin() || 506fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul TrialBBI2==I->second->begin()))) { 507fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (CommonTailLen > maxCommonTailLength) { 508fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SameTails.clear(); 509fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul maxCommonTailLength = CommonTailLen; 510fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul HighestMPIter = CurMPIter; 511fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SameTails.push_back(std::make_pair(CurMPIter, TrialBBI1)); 512fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 513fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (HighestMPIter == CurMPIter && 514fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul CommonTailLen == maxCommonTailLength) 515fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SameTails.push_back(std::make_pair(I, TrialBBI2)); 516fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 517fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (I==B) 518fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 519fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 520fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 521fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return maxCommonTailLength; 522fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 523fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 524fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// RemoveBlocksWithHash - Remove all blocks with hash CurHash from 525fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// MergePotentials, restoring branches at ends of blocks as appropriate. 526fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulvoid BranchFolder::RemoveBlocksWithHash(unsigned CurHash, 527fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock* SuccBB, 528fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock* PredBB) { 529fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MPIterator CurMPIter, B; 530fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (CurMPIter = prior(MergePotentials.end()), B = MergePotentials.begin(); 531fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul CurMPIter->first==CurHash; 532fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul --CurMPIter) { 533fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Put the unconditional branch back, if we need one. 534fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *CurMBB = CurMPIter->second; 535fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (SuccBB && CurMBB != PredBB) 536fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul FixTail(CurMBB, SuccBB, TII); 537fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (CurMPIter==B) 538fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 539fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 540fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (CurMPIter->first!=CurHash) 54174df2ef732abba668ca784190617023419c0b965Brian Paul CurMPIter++; 54274df2ef732abba668ca784190617023419c0b965Brian Paul MergePotentials.erase(CurMPIter, MergePotentials.end()); 54374df2ef732abba668ca784190617023419c0b965Brian Paul} 54474df2ef732abba668ca784190617023419c0b965Brian Paul 545fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// CreateCommonTailOnlyBlock - None of the blocks to be tail-merged consist 546fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul/// only of the common tail. Create a block that does by splitting one. 547fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulunsigned BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB, 548fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned maxCommonTailLength) { 549fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned i, commonTailIndex; 550fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned TimeEstimate = ~0U; 551fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (i=0, commonTailIndex=0; i<SameTails.size(); i++) { 552fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Use PredBB if possible; that doesn't require a new branch. 553fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (SameTails[i].first->second==PredBB) { 554fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul commonTailIndex = i; 555fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 556fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 557fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Otherwise, make a (fairly bogus) choice based on estimate of 558fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // how long it will take the various blocks to execute. 559fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned t = EstimateRuntime(SameTails[i].first->second->begin(), 560fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SameTails[i].second); 561fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (t<=TimeEstimate) { 562fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul TimeEstimate = t; 563fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul commonTailIndex = i; 564fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 565fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 566fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 567fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock::iterator BBI = SameTails[commonTailIndex].second; 568fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *MBB = SameTails[commonTailIndex].first->second; 569fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 570fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul DOUT << "\nSplitting " << MBB->getNumber() << ", size " << 571fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul maxCommonTailLength; 572fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 573fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI); 574fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SameTails[commonTailIndex].first->second = newMBB; 575fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SameTails[commonTailIndex].second = newMBB->begin(); 576fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // If we split PredBB, newMBB is the new predecessor. 577fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (PredBB==MBB) 578fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul PredBB = newMBB; 579fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 580fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul return commonTailIndex; 581fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul} 582fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 583fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// See if any of the blocks in MergePotentials (which all have a common single 584fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// successor, or all have no successor) can be tail-merged. If there is a 585fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// successor, any blocks in MergePotentials that are not tail-merged and 586fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// are not immediately before Succ must have an unconditional branch to 587fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// Succ added (but the predecessor/successor lists need no adjustment). 588fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// The lone predecessor of Succ that falls through into Succ, 589fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul// if any, is given in PredBB. 590fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 591fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paulbool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB, 592fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock* PredBB) { 593fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // It doesn't make sense to save a single instruction since tail merging 594fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // will add a jump. 595fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // FIXME: Ask the target to provide the threshold? 596fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned minCommonTailLength = (SuccBB ? 1 : 2) + 1; 597fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MadeChange = false; 598fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 599fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul DOUT << "\nTryMergeBlocks " << MergePotentials.size() << '\n'; 600fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 601fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Sort by hash value so that blocks with identical end sequences sort 602fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // together. 603fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul std::stable_sort(MergePotentials.begin(), MergePotentials.end(),MergeCompare); 604fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 605fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Walk through equivalence sets looking for actual exact matches. 606fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul while (MergePotentials.size() > 1) { 607fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned CurHash = prior(MergePotentials.end())->first; 608fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 609fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Build SameTails, identifying the set of blocks with this hash code 610fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // and with the maximum number of instructions in common. 611fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned maxCommonTailLength = ComputeSameTails(CurHash, 612fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul minCommonTailLength); 613fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 614fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // If we didn't find any pair that has at least minCommonTailLength 615fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // instructions in common, remove all blocks with this hash code and retry. 616fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (SameTails.empty()) { 617fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul RemoveBlocksWithHash(CurHash, SuccBB, PredBB); 618fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul continue; 619fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 620fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 621fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // If one of the blocks is the entire common tail (and not the entry 622fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // block, which we can't jump to), we can treat all blocks with this same 623fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // tail at once. Use PredBB if that is one of the possibilities, as that 624fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // will not introduce any extra branches. 625fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *EntryBB = MergePotentials.begin()->second-> 626fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul getParent()->begin(); 627fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul unsigned int commonTailIndex, i; 628fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (commonTailIndex=SameTails.size(), i=0; i<SameTails.size(); i++) { 629fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *MBB = SameTails[i].first->second; 630fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (MBB->begin() == SameTails[i].second && MBB != EntryBB) { 631fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul commonTailIndex = i; 632fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (MBB==PredBB) 633fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul break; 634fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 635fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 636fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 637fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (commonTailIndex==SameTails.size()) { 638fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // None of the blocks consist entirely of the common tail. 639fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Split a block so that one does. 640fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul commonTailIndex = CreateCommonTailOnlyBlock(PredBB, maxCommonTailLength); 641fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 642fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 643fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *MBB = SameTails[commonTailIndex].first->second; 644fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // MBB is common tail. Adjust all other BB's to jump to this one. 645fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Traversal must be forwards so erases work. 646fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul DOUT << "\nUsing common tail " << MBB->getNumber() << " for "; 647fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (unsigned int i=0; i<SameTails.size(); ++i) { 648fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (commonTailIndex==i) 649fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul continue; 650fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul DOUT << SameTails[i].first->second->getNumber() << ","; 651fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Hack the end off BB i, making it jump to BB commonTailIndex instead. 652fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul ReplaceTailWithBranchTo(SameTails[i].second, MBB); 653fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // BB i is no longer a predecessor of SuccBB; remove it from the worklist. 654fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MergePotentials.erase(SameTails[i].first); 655fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 656fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul DOUT << "\n"; 657fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // We leave commonTailIndex in the worklist in case there are other blocks 658a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // that match it with a smaller number of instructions. 659a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul MadeChange = true; 660a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul } 661a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul return MadeChange; 662a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul} 663a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul 664a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paulbool BranchFolder::TailMergeBlocks(MachineFunction &MF) { 665a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul 666a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul if (!EnableTailMerge) return false; 667a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul 668a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul MadeChange = false; 669a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul 670a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // First find blocks with no successors. 671a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul MergePotentials.clear(); 672a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) { 673a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul if (I->succ_empty()) 674a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul MergePotentials.push_back(std::make_pair(HashEndOfMBB(I, 2U), I)); 675a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul } 676a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // See if we can do any tail merging on those. 677a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul if (MergePotentials.size() < TailMergeThreshold && 678a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul MergePotentials.size() >= 2) 679a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul MadeChange |= TryMergeBlocks(NULL, NULL); 680a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul 681a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // Look at blocks (IBB) with multiple predecessors (PBB). 682a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // We change each predecessor to a canonical form, by 683a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // (1) temporarily removing any unconditional branch from the predecessor 684a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // to IBB, and 685a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // (2) alter conditional branches so they branch to the other block 686a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // not IBB; this may require adding back an unconditional branch to IBB 687a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // later, where there wasn't one coming in. E.g. 688a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // Bcc IBB 689a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // fallthrough to QBB 690a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // here becomes 691a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // Bncc QBB 692a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // with a conceptual B to IBB after that, which never actually exists. 693a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // With those changes, we see whether the predecessors' tails match, 694a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // and merge them if so. We change things out of canonical form and 695a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // back to the way they were later in the process. (OptimizeBranches 696a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // would undo some of this, but we can't use it, because we'd get into 697a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // a compile-time infinite loop repeatedly doing and undoing the same 698fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // transformations.) 699fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul 700fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) { 701fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (I->pred_size() >= 2 && I->pred_size() < TailMergeThreshold) { 702fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *IBB = I; 703fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *PredBB = prior(I); 704fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MergePotentials.clear(); 705fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul for (MachineBasicBlock::pred_iterator P = I->pred_begin(), 706fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul E2 = I->pred_end(); 707fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul P != E2; ++P) { 708fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock* PBB = *P; 709fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Skip blocks that loop to themselves, can't tail merge these. 710fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (PBB==IBB) 711fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul continue; 712fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock *TBB = 0, *FBB = 0; 713fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SmallVector<MachineOperand, 4> Cond; 714fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond)) { 715fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Failing case: IBB is the target of a cbr, and 716fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // we cannot reverse the branch. 717fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul SmallVector<MachineOperand, 4> NewCond(Cond); 718fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!Cond.empty() && TBB==IBB) { 719fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (TII->ReverseBranchCondition(NewCond)) 720fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul continue; 721fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // This is the QBB case described above 722fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (!FBB) 723fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul FBB = next(MachineFunction::iterator(PBB)); 724fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } 725fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // Failing case: the only way IBB can be reached from PBB is via 726fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // exception handling. Happens for landing pads. Would be nice 727fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul // to have a bit in the edge so we didn't have to do all this. 728fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (IBB->isLandingPad()) { 729fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineFunction::iterator IP = PBB; IP++; 730fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul MachineBasicBlock* PredNextBB = NULL; 731fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (IP!=MF.end()) 732fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul PredNextBB = IP; 733fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (TBB==NULL) { 734fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (IBB!=PredNextBB) // fallthrough 735fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul continue; 736fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul } else if (FBB) { 737fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (TBB!=IBB && FBB!=IBB) // cbr then ubr 738a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul continue; 739a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul } else if (Cond.empty()) { 740a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul if (TBB!=IBB) // ubr 741a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul continue; 742afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } else { 743fbd8f212c3866ec98c1d8c9d3db3ddb7e7c479a5Brian Paul if (TBB!=IBB && IBB!=PredNextBB) // cbr 744473e51f2fbfb003717bb88616ea585fc8d76f75eBrian Paul continue; 745afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 746afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 747afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Remove the unconditional branch at the end, if any. 748afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (TBB && (Cond.empty() || FBB)) { 749afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(*PBB); 750afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!Cond.empty()) 751a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // reinsert conditional branch only, for now 752afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(*PBB, (TBB==IBB) ? FBB : TBB, 0, NewCond); 753afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 754afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MergePotentials.push_back(std::make_pair(HashEndOfMBB(PBB, 1U), *P)); 755afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 756afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 757a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul if (MergePotentials.size() >= 2) 758afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange |= TryMergeBlocks(I, PredBB); 759afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Reinsert an unconditional branch if needed. 760afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // The 1 below can occur as a result of removing blocks in TryMergeBlocks. 761afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg PredBB = prior(I); // this may have been changed in TryMergeBlocks 762afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MergePotentials.size()==1 && 763afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MergePotentials.begin()->second != PredBB) 764afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg FixTail(MergePotentials.begin()->second, I, TII); 765afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 766afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 767afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return MadeChange; 768afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg} 769afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 770afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg//===----------------------------------------------------------------------===// 771afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg// Branch Optimization 772afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg//===----------------------------------------------------------------------===// 773afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 774afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgbool BranchFolder::OptimizeBranches(MachineFunction &MF) { 775afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = false; 776afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 777afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Make sure blocks are numbered in order 778afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MF.RenumberBlocks(); 779afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 780afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg for (MachineFunction::iterator I = ++MF.begin(), E = MF.end(); I != E; ) { 781afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *MBB = I++; 782afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg OptimizeBlock(MBB); 783afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 784afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If it is dead, remove it. 785afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MBB->pred_empty()) { 786afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg RemoveDeadBlock(MBB); 787a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul MadeChange = true; 788afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++NumDeadBlocks; 789afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 790afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 791afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return MadeChange; 792afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg} 793afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 794afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 795afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// CanFallThrough - Return true if the specified block (with the specified 796afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// branch condition) can implicitly transfer control to the block after it by 797afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// falling off the end of it. This should return false if it can reach the 798afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// block after it, but it uses an explicit branch to do so (e.g. a table jump). 799afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// 800afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// True is a conservative answer. 801afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// 802afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgbool BranchFolder::CanFallThrough(MachineBasicBlock *CurBB, 803afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool BranchUnAnalyzable, 804afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *TBB, 805afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *FBB, 806afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg const SmallVectorImpl<MachineOperand> &Cond) { 807afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineFunction::iterator Fallthrough = CurBB; 808afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++Fallthrough; 809afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If FallthroughBlock is off the end of the function, it can't fall through. 810afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (Fallthrough == CurBB->getParent()->end()) 811afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return false; 812afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 813afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If FallthroughBlock isn't a successor of CurBB, no fallthrough is possible. 814afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!CurBB->isSuccessor(Fallthrough)) 815afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return false; 816afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 817afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If we couldn't analyze the branch, assume it could fall through. 818afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (BranchUnAnalyzable) return true; 819afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 820afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If there is no branch, control always falls through. 821afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (TBB == 0) return true; 822afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 823afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If there is some explicit branch to the fallthrough block, it can obviously 824afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // reach, even though the branch should get folded to fall through implicitly. 825afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MachineFunction::iterator(TBB) == Fallthrough || 826afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineFunction::iterator(FBB) == Fallthrough) 827afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return true; 828afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 829afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If it's an unconditional branch to some block not the fall through, it 830afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // doesn't fall through. 831afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (Cond.empty()) return false; 832afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 833afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Otherwise, if it is conditional and has no explicit false block, it falls 834afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // through. 835afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return FBB == 0; 836afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg} 837afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 838afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// CanFallThrough - Return true if the specified can implicitly transfer 839afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// control to the block after it by falling off the end of it. This should 840afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// return false if it can reach the block after it, but it uses an explicit 841afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// branch to do so (e.g. a table jump). 842afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// 843afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// True is a conservative answer. 844afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// 845afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgbool BranchFolder::CanFallThrough(MachineBasicBlock *CurBB) { 846afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *TBB = 0, *FBB = 0; 847afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg SmallVector<MachineOperand, 4> Cond; 848afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool CurUnAnalyzable = TII->AnalyzeBranch(*CurBB, TBB, FBB, Cond); 849afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return CanFallThrough(CurBB, CurUnAnalyzable, TBB, FBB, Cond); 850afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg} 851afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 852afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// IsBetterFallthrough - Return true if it would be clearly better to 853afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// fall-through to MBB1 than to fall through into MBB2. This has to return 854afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// a strict ordering, returning true for both (MBB1,MBB2) and (MBB2,MBB1) will 855afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// result in infinite loops. 856afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgstatic bool IsBetterFallthrough(MachineBasicBlock *MBB1, 857afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *MBB2) { 858a8b07a539b42b04111f48aa145bc3b2633fd5387Brian Paul // Right now, we use a simple heuristic. If MBB2 ends with a call, and 859afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // MBB1 doesn't, we prefer to fall through into MBB1. This allows us to 860afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // optimize branches that branch to either a return block or an assert block 861afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // into a fallthrough to the return. 862afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MBB1->empty() || MBB2->empty()) return false; 863afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 864afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If there is a clear successor ordering we make sure that one block 865afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // will fall through to the next 866afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MBB1->isSuccessor(MBB2)) return true; 867afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MBB2->isSuccessor(MBB1)) return false; 868afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 869afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineInstr *MBB1I = --MBB1->end(); 870afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineInstr *MBB2I = --MBB2->end(); 871afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return MBB2I->getDesc().isCall() && !MBB1I->getDesc().isCall(); 872afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg} 873afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 874afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// OptimizeBlock - Analyze and optimize control flow related to the specified 875afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg/// block. This is never called on the entry block. 876afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtgvoid BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) { 877afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineFunction::iterator FallThrough = MBB; 878afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++FallThrough; 879afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 880afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If this block is empty, make everyone use its fall-through, not the block 881afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // explicitly. Landing pads should not do this since the landing-pad table 882afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // points to this block. 883afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MBB->empty() && !MBB->isLandingPad()) { 884afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Dead block? Leave for cleanup later. 885afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MBB->pred_empty()) return; 886afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 887afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (FallThrough == MBB->getParent()->end()) { 888afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // TODO: Simplify preds to not branch here if possible! 889afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } else { 890afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Rewrite all predecessors of the old block to go to the fallthrough 891afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // instead. 892afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg while (!MBB->pred_empty()) { 893afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *Pred = *(MBB->pred_end()-1); 894afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg Pred->ReplaceUsesOfBlockWith(MBB, FallThrough); 895afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 896afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 897afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If MBB was the target of a jump table, update jump tables to go to the 898afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // fallthrough instead. 899afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MBB->getParent()->getJumpTableInfo()-> 900afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ReplaceMBBInJumpTables(MBB, FallThrough); 901afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 902afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 903afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return; 904afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 905afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 906afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Check to see if we can simplify the terminator of the block before this 907afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // one. 908afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock &PrevBB = *prior(MachineFunction::iterator(MBB)); 909afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 910afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *PriorTBB = 0, *PriorFBB = 0; 911afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg SmallVector<MachineOperand, 4> PriorCond; 912afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool PriorUnAnalyzable = 913afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->AnalyzeBranch(PrevBB, PriorTBB, PriorFBB, PriorCond); 914afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!PriorUnAnalyzable) { 915afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the CFG for the prior block has extra edges, remove them. 916afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange |= PrevBB.CorrectExtraCFGEdges(PriorTBB, PriorFBB, 917afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg !PriorCond.empty()); 918afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 919afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the previous branch is conditional and both conditions go to the same 920afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // destination, remove the branch, replacing it with an unconditional one or 921afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // a fall-through. 922afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PriorTBB && PriorTBB == PriorFBB) { 923afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(PrevBB); 924afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg PriorCond.clear(); 925afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PriorTBB != MBB) 926afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond); 927afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 928afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++NumBranchOpts; 929afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return OptimizeBlock(MBB); 930afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 931afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 932afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the previous branch *only* branches to *this* block (conditional or 933afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // not) remove the branch. 934afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PriorTBB == MBB && PriorFBB == 0) { 935afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(PrevBB); 936afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 937afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++NumBranchOpts; 938afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return OptimizeBlock(MBB); 939afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 940afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 941afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the prior block branches somewhere else on the condition and here if 942afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // the condition is false, remove the uncond second branch. 943afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PriorFBB == MBB) { 944afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(PrevBB); 945afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond); 946afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 947afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++NumBranchOpts; 948afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return OptimizeBlock(MBB); 949afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 950afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 951afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the prior block branches here on true and somewhere else on false, and 952afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // if the branch condition is reversible, reverse the branch to create a 953afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // fall-through. 954afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PriorTBB == MBB) { 955afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg SmallVector<MachineOperand, 4> NewPriorCond(PriorCond); 956afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!TII->ReverseBranchCondition(NewPriorCond)) { 957afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(PrevBB); 958afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(PrevBB, PriorFBB, 0, NewPriorCond); 959afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 960afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++NumBranchOpts; 961afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return OptimizeBlock(MBB); 962afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 963afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 964afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 965afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If this block doesn't fall through (e.g. it ends with an uncond branch or 966afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // has no successors) and if the pred falls through into this block, and if 967afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // it would otherwise fall through into the block after this, move this 968afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // block to the end of the function. 969afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // 970afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // We consider it more likely that execution will stay in the function (e.g. 971afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // due to loops) than it is to exit it. This asserts in loops etc, moving 972afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // the assert condition out of the loop body. 973afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!PriorCond.empty() && PriorFBB == 0 && 974afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineFunction::iterator(PriorTBB) == FallThrough && 975afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg !CanFallThrough(MBB)) { 976afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool DoTransform = true; 977afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 978afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // We have to be careful that the succs of PredBB aren't both no-successor 979afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // blocks. If neither have successors and if PredBB is the second from 980afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // last block in the function, we'd just keep swapping the two blocks for 981afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // last. Only do the swap if one is clearly better to fall through than 982afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // the other. 983afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (FallThrough == --MBB->getParent()->end() && 984afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg !IsBetterFallthrough(PriorTBB, MBB)) 985afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg DoTransform = false; 986afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 987afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // We don't want to do this transformation if we have control flow like: 988afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // br cond BB2 989afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // BB1: 990afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // .. 991afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // jmp BBX 992afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // BB2: 993afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // .. 994afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // ret 995afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // 996afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // In this case, we could actually be moving the return block *into* a 997afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // loop! 998afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (DoTransform && !MBB->succ_empty() && 999afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg (!CanFallThrough(PriorTBB) || PriorTBB->empty())) 1000afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg DoTransform = false; 1001afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1002afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1003afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (DoTransform) { 1004afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Reverse the branch so we will fall through on the previous true cond. 1005afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg SmallVector<MachineOperand, 4> NewPriorCond(PriorCond); 1006afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!TII->ReverseBranchCondition(NewPriorCond)) { 1007afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg DOUT << "\nMoving MBB: " << *MBB; 1008afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg DOUT << "To make fallthrough to: " << *PriorTBB << "\n"; 1009afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1010afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(PrevBB); 1011afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(PrevBB, MBB, 0, NewPriorCond); 1012afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1013afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Move this block to the end of the function. 1014afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MBB->moveAfter(--MBB->getParent()->end()); 1015afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 1016afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++NumBranchOpts; 1017afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return; 1018afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1019afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1020afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1021afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1022afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1023afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Analyze the branch in the current block. 1024afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *CurTBB = 0, *CurFBB = 0; 1025afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg SmallVector<MachineOperand, 4> CurCond; 1026afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool CurUnAnalyzable = TII->AnalyzeBranch(*MBB, CurTBB, CurFBB, CurCond); 1027afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!CurUnAnalyzable) { 1028afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the CFG for the prior block has extra edges, remove them. 1029afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange |= MBB->CorrectExtraCFGEdges(CurTBB, CurFBB, !CurCond.empty()); 1030afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1031afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If this is a two-way branch, and the FBB branches to this block, reverse 1032afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // the condition so the single-basic-block loop is faster. Instead of: 1033afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Loop: xxx; jcc Out; jmp Loop 1034afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // we want: 1035afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Loop: xxx; jncc Loop; jmp Out 1036afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (CurTBB && CurFBB && CurFBB == MBB && CurTBB != MBB) { 1037afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg SmallVector<MachineOperand, 4> NewCond(CurCond); 1038afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!TII->ReverseBranchCondition(NewCond)) { 1039afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(*MBB); 1040afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(*MBB, CurFBB, CurTBB, NewCond); 1041afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 1042afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++NumBranchOpts; 1043afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return OptimizeBlock(MBB); 1044afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1045afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1046afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1047afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1048afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If this branch is the only thing in its block, see if we can forward 1049afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // other blocks across it. 1050afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (CurTBB && CurCond.empty() && CurFBB == 0 && 1051afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MBB->begin()->getDesc().isBranch() && CurTBB != MBB) { 1052afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // This block may contain just an unconditional branch. Because there can 1053afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // be 'non-branch terminators' in the block, try removing the branch and 1054afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // then seeing if the block is empty. 1055afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(*MBB); 1056afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1057afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If this block is just an unconditional branch to CurTBB, we can 1058afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // usually completely eliminate the block. The only case we cannot 1059afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // completely eliminate the block is when the block before this one 1060afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // falls through into MBB and we can't understand the prior block's branch 1061afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // condition. 1062afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (MBB->empty()) { 1063afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool PredHasNoFallThrough = TII->BlockHasNoFallThrough(PrevBB); 1064afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PredHasNoFallThrough || !PriorUnAnalyzable || 1065afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg !PrevBB.isSuccessor(MBB)) { 1066afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the prior block falls through into us, turn it into an 1067afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // explicit branch to us to make updates simpler. 1068afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!PredHasNoFallThrough && PrevBB.isSuccessor(MBB) && 1069afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg PriorTBB != MBB && PriorFBB != MBB) { 1070afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PriorTBB == 0) { 1071afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg assert(PriorCond.empty() && PriorFBB == 0 && 1072afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg "Bad branch analysis"); 1073afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg PriorTBB = MBB; 1074afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } else { 1075afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg assert(PriorFBB == 0 && "Machine CFG out of date!"); 1076afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg PriorFBB = MBB; 1077afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1078afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->RemoveBranch(PrevBB); 1079afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(PrevBB, PriorTBB, PriorFBB, PriorCond); 1080afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1081afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1082afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Iterate through all the predecessors, revectoring each in-turn. 1083afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg size_t PI = 0; 1084afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool DidChange = false; 1085afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool HasBranchToSelf = false; 1086afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg while(PI != MBB->pred_size()) { 1087afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *PMBB = *(MBB->pred_begin() + PI); 1088afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PMBB == MBB) { 1089afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If this block has an uncond branch to itself, leave it. 1090afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++PI; 1091afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg HasBranchToSelf = true; 1092afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } else { 1093afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg DidChange = true; 1094afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg PMBB->ReplaceUsesOfBlockWith(MBB, CurTBB); 1095afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1096afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1097afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1098afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Change any jumptables to go to the new MBB. 1099afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MBB->getParent()->getJumpTableInfo()-> 1100afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ReplaceMBBInJumpTables(MBB, CurTBB); 1101afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (DidChange) { 1102afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg ++NumBranchOpts; 1103afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 1104afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!HasBranchToSelf) return; 1105afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1106afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1107afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1108afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1109afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Add the branch back if the block is more than just an uncond branch. 1110afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(*MBB, CurTBB, 0, CurCond); 1111afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1112afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1113afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1114afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the prior block doesn't fall through into this block, and if this 1115afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // block doesn't fall through into some other block, see if we can find a 1116afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // place to move this block where a fall-through will happen. 1117afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!CanFallThrough(&PrevBB, PriorUnAnalyzable, 1118afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg PriorTBB, PriorFBB, PriorCond)) { 1119afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Now we know that there was no fall-through into this block, check to 1120afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // see if it has a fall-through into its successor. 1121afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg bool CurFallsThru = CanFallThrough(MBB, CurUnAnalyzable, CurTBB, CurFBB, 1122afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg CurCond); 1123afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1124afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!MBB->isLandingPad()) { 1125afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Check all the predecessors of this block. If one of them has no fall 1126afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // throughs, move this block right after it. 1127afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), 1128afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg E = MBB->pred_end(); PI != E; ++PI) { 1129afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Analyze the branch at the end of the pred. 1130afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *PredBB = *PI; 1131afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineFunction::iterator PredFallthrough = PredBB; ++PredFallthrough; 1132afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (PredBB != MBB && !CanFallThrough(PredBB) 1133afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg && (!CurFallsThru || !CurTBB || !CurFBB) 1134afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg && (!CurFallsThru || MBB->getNumber() >= PredBB->getNumber())) { 1135afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the current block doesn't fall through, just move it. 1136afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If the current block can fall through and does not end with a 1137afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // conditional branch, we need to append an unconditional jump to 1138afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // the (current) next block. To avoid a possible compile-time 1139afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // infinite loop, move blocks only backward in this case. 1140afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Also, if there are already 2 branches here, we cannot add a third; 1141afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // this means we have the case 1142645c1cef13475db0db6433574807ee01ff0ceb28Brian Paul // Bcc next 1143afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // B elsewhere 1144afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // next: 1145afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (CurFallsThru) { 1146afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *NextBB = next(MachineFunction::iterator(MBB)); 1147afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg CurCond.clear(); 1148afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg TII->InsertBranch(*MBB, NextBB, 0, CurCond); 1149afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1150afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MBB->moveAfter(PredBB); 1151afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 1152afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return OptimizeBlock(MBB); 1153afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1154afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1155afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1156afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1157afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (!CurFallsThru) { 1158afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Check all successors to see if we can move this block before it. 1159afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(), 1160afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg E = MBB->succ_end(); SI != E; ++SI) { 1161afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Analyze the branch at the end of the block before the succ. 1162afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineBasicBlock *SuccBB = *SI; 1163afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MachineFunction::iterator SuccPrev = SuccBB; --SuccPrev; 1164afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg std::vector<MachineOperand> SuccPrevCond; 1165afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1166afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // If this block doesn't already fall-through to that successor, and if 1167afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // the succ doesn't already have a block that can fall through into it, 1168afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // and if the successor isn't an EH destination, we can arrange for the 1169afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // fallthrough to happen. 1170afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (SuccBB != MBB && !CanFallThrough(SuccPrev) && 1171afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg !SuccBB->isLandingPad()) { 1172afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MBB->moveBefore(SuccBB); 1173afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 1174afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return OptimizeBlock(MBB); 1175afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1176afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1177afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg 1178afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // Okay, there is no really great place to put this block. If, however, 1179afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // the block before this one would be a fall-through if this block were 1180afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg // removed, move this block to the end of the function. 1181afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg if (FallThrough != MBB->getParent()->end() && 1182afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg PrevBB.isSuccessor(FallThrough)) { 1183afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MBB->moveAfter(--MBB->getParent()->end()); 1184afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg MadeChange = true; 1185afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg return; 1186afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1187afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1188afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg } 1189afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg} 1190afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1cjtg