PHIElimination.cpp revision 1cbe4d0ad0888e50858cca83cf2a0d3083709513
1bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner//===-- PhiElimination.cpp - Eliminate PHI nodes by inserting copies ------===// 2b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 3b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// The LLVM Compiler Infrastructure 4b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 5b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// This file was developed by the LLVM research group and is distributed under 6b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// the University of Illinois Open Source License. See LICENSE.TXT for details. 7b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 8b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell//===----------------------------------------------------------------------===// 9bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner// 10bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner// This pass eliminates machine instruction PHI nodes by inserting copy 11bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner// instructions. This destroys SSA information, but is the desired input for 12bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner// some register allocators. 13bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner// 14bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner//===----------------------------------------------------------------------===// 15bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 16bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner#include "llvm/CodeGen/MachineFunctionPass.h" 17bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner#include "llvm/CodeGen/MachineInstr.h" 18bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner#include "llvm/CodeGen/SSARegMap.h" 19bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner#include "llvm/CodeGen/LiveVariables.h" 203501feab811c86c9659248a4875fc31a3165f84dChris Lattner#include "llvm/Target/TargetInstrInfo.h" 21bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner#include "llvm/Target/TargetMachine.h" 22572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner#include "llvm/Support/CFG.h" 23bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 24d0fde30ce850b78371fd1386338350591f9ff494Brian Gaekenamespace llvm { 25d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 26bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattnernamespace { 27bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner struct PNE : public MachineFunctionPass { 28bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner bool runOnMachineFunction(MachineFunction &Fn) { 29bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner bool Changed = false; 30bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 31bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // Eliminate PHI instructions by inserting copies into predecessor blocks. 32bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // 33bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) 34bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner Changed |= EliminatePHINodes(Fn, *I); 35bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 36bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner //std::cerr << "AFTER PHI NODE ELIM:\n"; 37bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner //Fn.dump(); 38bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner return Changed; 39bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner } 40bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 41bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 42bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner AU.addPreserved<LiveVariables>(); 43bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner MachineFunctionPass::getAnalysisUsage(AU); 44bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner } 45bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 46bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner private: 47bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions 48bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner /// in predecessor basic blocks. 49bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner /// 50bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB); 51bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner }; 52bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 53bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner RegisterPass<PNE> X("phi-node-elimination", 54bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner "Eliminate PHI nodes for register allocation"); 55bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner} 56bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 57d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 58bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattnerconst PassInfo *PHIEliminationID = X.getPassInfo(); 59bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 60bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions in 61bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner/// predecessor basic blocks. 62bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner/// 63bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattnerbool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { 640416d2a70aea644c3e0c06301c29f3b81ec1e42dChris Lattner if (MBB.empty() || MBB.front()->getOpcode() != TargetInstrInfo::PHI) 65bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner return false; // Quick exit for normal case... 66bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 67bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner LiveVariables *LV = getAnalysisToUpdate<LiveVariables>(); 68bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner const TargetInstrInfo &MII = MF.getTarget().getInstrInfo(); 69bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner const MRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo(); 70bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 71bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner while (MBB.front()->getOpcode() == TargetInstrInfo::PHI) { 72bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner MachineInstr *MI = MBB.front(); 73bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // Unlink the PHI node from the basic block... but don't delete the PHI yet 74bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner MBB.erase(MBB.begin()); 75bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 761cbe4d0ad0888e50858cca83cf2a0d3083709513Chris Lattner assert(MRegisterInfo::isVirtualRegister(MI->getOperand(0).getReg()) && 77bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner "PHI node doesn't write virt reg?"); 78bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 79bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner unsigned DestReg = MI->getOperand(0).getAllocatedRegNum(); 80bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 81bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // Create a new register for the incoming PHI arguments 82bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(DestReg); 83bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner unsigned IncomingReg = MF.getSSARegMap()->createVirtualRegister(RC); 84bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 85927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // Insert a register to register copy in the top of the current block (but 86bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // after any remaining phi nodes) which copies the new incoming register 87bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // into the phi node destination. 88bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // 89bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner MachineBasicBlock::iterator AfterPHIsIt = MBB.begin(); 90a13f0d3f4159b1f54bcfc733ccd94977b020ea56Chris Lattner while (AfterPHIsIt != MBB.end() && 91a13f0d3f4159b1f54bcfc733ccd94977b020ea56Chris Lattner (*AfterPHIsIt)->getOpcode() == TargetInstrInfo::PHI) 92a13f0d3f4159b1f54bcfc733ccd94977b020ea56Chris Lattner ++AfterPHIsIt; // Skip over all of the PHI nodes... 93bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC); 94927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner 95927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // Update live variable information if there is any... 96927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner if (LV) { 97927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner MachineInstr *PHICopy = *(AfterPHIsIt-1); 98927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner 99927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // Add information to LiveVariables to know that the incoming value is 100b52e0241c03a257f96bd9c77788eff5b1a7fd437Chris Lattner // killed. Note that because the value is defined in several places (once 101b52e0241c03a257f96bd9c77788eff5b1a7fd437Chris Lattner // each for each incoming block), the "def" block and instruction fields 102b52e0241c03a257f96bd9c77788eff5b1a7fd437Chris Lattner // for the VarInfo is not filled in. 103927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // 104b52e0241c03a257f96bd9c77788eff5b1a7fd437Chris Lattner LV->addVirtualRegisterKilled(IncomingReg, &MBB, PHICopy); 105bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 106927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // Since we are going to be deleting the PHI node, if it is the last use 107927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // of any registers, or if the value itself is dead, we need to move this 108927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // information over to the new copy we just inserted... 109927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // 110927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner std::pair<LiveVariables::killed_iterator, LiveVariables::killed_iterator> 111927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner RKs = LV->killed_range(MI); 112572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner std::vector<std::pair<MachineInstr*, unsigned> > Range; 113927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner if (RKs.first != RKs.second) { 114572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Copy the range into a vector... 115572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner Range.assign(RKs.first, RKs.second); 116572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner 117572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Delete the range... 118927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner LV->removeVirtualRegistersKilled(RKs.first, RKs.second); 119572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner 120572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Add all of the kills back, which will update the appropriate info... 121572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner for (unsigned i = 0, e = Range.size(); i != e; ++i) 122572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner LV->addVirtualRegisterKilled(Range[i].second, &MBB, PHICopy); 123927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner } 124927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner 125927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner RKs = LV->dead_range(MI); 126927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner if (RKs.first != RKs.second) { 127572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Works as above... 128572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner Range.assign(RKs.first, RKs.second); 129927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner LV->removeVirtualRegistersDead(RKs.first, RKs.second); 130572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner for (unsigned i = 0, e = Range.size(); i != e; ++i) 131572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner LV->addVirtualRegisterDead(Range[i].second, &MBB, PHICopy); 132927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner } 133927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner } 134bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 135927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // Now loop over all of the incoming arguments, changing them to copy into 136bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // the IncomingReg register in the corresponding predecessor basic block. 137bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // 138bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) { 139bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner MachineOperand &opVal = MI->getOperand(i-1); 140bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 141bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // Get the MachineBasicBlock equivalent of the BasicBlock that is the 142927ce5dfaea00453889080cd1c6daf3eb197ad74Chris Lattner // source path the PHI. 143bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock(); 144bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 14598719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // Figure out where to insert the copy, which is at the end of the 14698719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // predecessor basic block, but before any terminator/branch 14798719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // instructions... 14898719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner MachineBasicBlock::iterator I = opBlock.end(); 14998719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner if (I != opBlock.begin()) { // Handle empty blocks 15098719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner --I; 15198719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // must backtrack over ALL the branches in the previous block 15298719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner while (MII.isTerminatorInstr((*I)->getOpcode()) && 15398719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner I != opBlock.begin()) 15498719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner --I; 15598719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner 15698719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // move back to the first branch instruction so new instructions 15798719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // are inserted right in front of it and not in front of a non-branch 15898719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner if (!MII.isTerminatorInstr((*I)->getOpcode())) 15998719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner ++I; 16098719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner } 16198719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner 162bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // Check to make sure we haven't already emitted the copy for this block. 163bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // This can happen because PHI nodes may have multiple entries for the 164bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // same basic block. It doesn't matter which entry we use though, because 165bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // all incoming values are guaranteed to be the same for a particular bb. 166bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // 16798719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // If we emitted a copy for this basic block already, it will be right 16898719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // where we want to insert one now. Just check for a definition of the 16998719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner // register we are interested in! 170bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // 171bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner bool HaveNotEmitted = true; 17298719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner 17398719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner if (I != opBlock.begin()) { 17498719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner MachineInstr *PrevInst = *(I-1); 17598719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner for (unsigned i = 0, e = PrevInst->getNumOperands(); i != e; ++i) { 17698719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner MachineOperand &MO = PrevInst->getOperand(i); 1771cbe4d0ad0888e50858cca83cf2a0d3083709513Chris Lattner if (MO.isRegister() && MO.getReg() == IncomingReg) 1784d7af65903cbc858464362e70a6adf499982ec8aAlkis Evlogimenos if (MO.isDef()) { 17998719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner HaveNotEmitted = false; 18098719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner break; 18198719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner } 182bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner } 18398719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner } 184bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 185572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner if (HaveNotEmitted) { // If the copy has not already been emitted, do it. 1861cbe4d0ad0888e50858cca83cf2a0d3083709513Chris Lattner assert(MRegisterInfo::isVirtualRegister(opVal.getReg()) && 18798719d7cdc693c077d179fe3461ce625d6faef34Chris Lattner "Machine PHI Operands must all be virtual registers!"); 188572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner unsigned SrcReg = opVal.getReg(); 189572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner RegInfo->copyRegToReg(opBlock, I, IncomingReg, SrcReg, RC); 190572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner 191572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Now update live variable information if we have it. 192572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner if (LV) { 193572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // We want to be able to insert a kill of the register if this PHI 194572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // (aka, the copy we just inserted) is the last use of the source 195572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // value. Live variable analysis conservatively handles this by 196572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // saying that the value is live until the end of the block the PHI 197572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // entry lives in. If the value really is dead at the PHI copy, there 198572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // will be no successor blocks which have the value live-in. 199572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // 200572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Check to see if the copy is the last use, and if so, update the 201572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // live variables information so that it knows the copy source 202572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // instruction kills the incoming value. 203572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // 204572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner LiveVariables::VarInfo &InRegVI = LV->getVarInfo(SrcReg); 205572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner 20608d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner // Loop over all of the successors of the basic block, checking to see 20708d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner // if the value is either live in the block, or if it is killed in the 20808d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner // block. Also check to see if this register is in use by another PHI 20908d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner // node which has not yet been eliminated. If so, it will be killed 21008d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner // at an appropriate point later. 211572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // 212572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner bool ValueIsLive = false; 2139e2dd8f8d7c995721584d8c7add309e5d9cb1051Chris Lattner const BasicBlock *BB = opBlock.getBasicBlock(); 2149e2dd8f8d7c995721584d8c7add309e5d9cb1051Chris Lattner for (succ_const_iterator SI = succ_begin(BB), E = succ_end(BB); 21508d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner SI != E && !ValueIsLive; ++SI) { 216572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner const std::pair<MachineBasicBlock*, unsigned> & 217572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner SuccInfo = LV->getBasicBlockInfo(*SI); 218572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner 219572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Is it alive in this successor? 220572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner unsigned SuccIdx = SuccInfo.second; 221572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner if (SuccIdx < InRegVI.AliveBlocks.size() && 222572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner InRegVI.AliveBlocks[SuccIdx]) { 223572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner ValueIsLive = true; 224572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner break; 225572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner } 226572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner 227572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Is it killed in this successor? 228572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner MachineBasicBlock *MBB = SuccInfo.first; 229572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i) 230572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner if (InRegVI.Kills[i].first == MBB) { 231572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner ValueIsLive = true; 232572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner break; 233572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner } 23408d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner 23508d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner // Is it used by any PHI instructions in this block? 23608d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner if (ValueIsLive) break; 23708d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner 23808d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner // Loop over all of the PHIs in this successor, checking to see if 23908d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner // the register is being used... 24008d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner for (MachineBasicBlock::iterator BBI = MBB->begin(), E=MBB->end(); 24108d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner BBI != E && (*BBI)->getOpcode() == TargetInstrInfo::PHI; 24208d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner ++BBI) 24308d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner for (unsigned i = 1, e = (*BBI)->getNumOperands(); i < e; i += 2) 24408d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner if ((*BBI)->getOperand(i).getReg() == SrcReg) { 24508d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner ValueIsLive = true; 24608d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner break; 24708d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner } 248572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner } 249572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner 250572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // Okay, if we now know that the value is not live out of the block, 251572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // we can add a kill marker to the copy we inserted saying that it 252572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // kills the incoming value! 253572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner // 25408d2e4e09adc53aa93c08c8327d2f5f2814acb74Chris Lattner if (!ValueIsLive) 255572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner LV->addVirtualRegisterKilled(SrcReg, &opBlock, *(I-1)); 256572c77066808fc0e9ee1d212dab227f28bf5e28aChris Lattner } 257bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner } 258bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner } 259bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 260bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner // really delete the PHI instruction now! 261bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner delete MI; 262bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner } 263bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner 264bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner return true; 265bc40e898e153c9b81f246a7971eaac7b14446c49Chris Lattner} 266d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 267d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke} // End llvm namespace 268