InlineFunction.cpp revision f7703df4968084c18c248c1feea9961c19a32e6a
1//===- InlineFunction.cpp - Code to perform function inlining -------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements inlining of a function into a call site, resolving 11// parameters and the return value as appropriate. 12// 13// FIXME: This pass should transform alloca instructions in the called function 14// into malloc/free pairs! Or perhaps it should refuse to inline them! 15// 16//===----------------------------------------------------------------------===// 17 18#include "llvm/Transforms/Utils/Cloning.h" 19#include "llvm/Constant.h" 20#include "llvm/DerivedTypes.h" 21#include "llvm/Module.h" 22#include "llvm/Instructions.h" 23#include "llvm/Intrinsics.h" 24#include "llvm/Support/CallSite.h" 25#include "llvm/Transforms/Utils/Local.h" 26using namespace llvm; 27 28bool llvm::InlineFunction(CallInst *CI) { return InlineFunction(CallSite(CI)); } 29bool llvm::InlineFunction(InvokeInst *II) {return InlineFunction(CallSite(II));} 30 31// InlineFunction - This function inlines the called function into the basic 32// block of the caller. This returns false if it is not possible to inline this 33// call. The program is still in a well defined state if this occurs though. 34// 35// Note that this only does one level of inlining. For example, if the 36// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 37// exists in the instruction stream. Similiarly this will inline a recursive 38// function by one level. 39// 40bool llvm::InlineFunction(CallSite CS) { 41 Instruction *TheCall = CS.getInstruction(); 42 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 43 "Instruction not in function!"); 44 45 const Function *CalledFunc = CS.getCalledFunction(); 46 if (CalledFunc == 0 || // Can't inline external function or indirect 47 CalledFunc->isExternal() || // call, or call to a vararg function! 48 CalledFunc->getFunctionType()->isVarArg()) return false; 49 50 BasicBlock *OrigBB = TheCall->getParent(); 51 Function *Caller = OrigBB->getParent(); 52 53 // We want to clone the entire callee function into the whole between the 54 // "starter" and "ender" blocks. How we accomplish this depends on whether 55 // this is an invoke instruction or a call instruction. 56 57 BasicBlock *InvokeDest = 0; // Exception handling destination 58 std::vector<Value*> InvokeDestPHIValues; // Values for PHI nodes in InvokeDest 59 BasicBlock *AfterCallBB; 60 61 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 62 InvokeDest = II->getExceptionalDest(); 63 64 // If there are PHI nodes in the exceptional destination block, we need to 65 // keep track of which values came into them from this invoke, then remove 66 // the entry for this block. 67 for (BasicBlock::iterator I = InvokeDest->begin(); 68 PHINode *PN = dyn_cast<PHINode>(I); ++I) { 69 // Save the value to use for this edge... 70 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(OrigBB)); 71 } 72 73 // Add an unconditional branch to make this look like the CallInst case... 74 BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall); 75 76 // Split the basic block. This guarantees that no PHI nodes will have to be 77 // updated due to new incoming edges, and make the invoke case more 78 // symmetric to the call case. 79 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 80 CalledFunc->getName()+".entry"); 81 82 // Remove (unlink) the InvokeInst from the function... 83 OrigBB->getInstList().remove(TheCall); 84 85 } else { // It's a call 86 // If this is a call instruction, we need to split the basic block that the 87 // call lives in. 88 // 89 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 90 CalledFunc->getName()+".entry"); 91 // Remove (unlink) the CallInst from the function... 92 AfterCallBB->getInstList().remove(TheCall); 93 } 94 95 // If we have a return value generated by this call, convert it into a PHI 96 // node that gets values from each of the old RET instructions in the original 97 // function. 98 // 99 PHINode *PHI = 0; 100 if (!TheCall->use_empty()) { 101 // The PHI node should go at the front of the new basic block to merge all 102 // possible incoming values. 103 // 104 PHI = new PHINode(CalledFunc->getReturnType(), TheCall->getName(), 105 AfterCallBB->begin()); 106 107 // Anything that used the result of the function call should now use the PHI 108 // node as their operand. 109 // 110 TheCall->replaceAllUsesWith(PHI); 111 } 112 113 // Get an iterator to the last basic block in the function, which will have 114 // the new function inlined after it. 115 // 116 Function::iterator LastBlock = &Caller->back(); 117 118 // Calculate the vector of arguments to pass into the function cloner... 119 std::map<const Value*, Value*> ValueMap; 120 assert(std::distance(CalledFunc->abegin(), CalledFunc->aend()) == 121 std::distance(CS.arg_begin(), CS.arg_end()) && 122 "No varargs calls can be inlined!"); 123 124 CallSite::arg_iterator AI = CS.arg_begin(); 125 for (Function::const_aiterator I = CalledFunc->abegin(), E=CalledFunc->aend(); 126 I != E; ++I, ++AI) 127 ValueMap[I] = *AI; 128 129 // Since we are now done with the Call/Invoke, we can delete it. 130 delete TheCall; 131 132 // Make a vector to capture the return instructions in the cloned function... 133 std::vector<ReturnInst*> Returns; 134 135 // Do all of the hard part of cloning the callee into the caller... 136 CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i"); 137 138 // Loop over all of the return instructions, turning them into unconditional 139 // branches to the merge point now... 140 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 141 ReturnInst *RI = Returns[i]; 142 BasicBlock *BB = RI->getParent(); 143 144 // Add a branch to the merge point where the PHI node lives if it exists. 145 new BranchInst(AfterCallBB, RI); 146 147 if (PHI) { // The PHI node should include this value! 148 assert(RI->getReturnValue() && "Ret should have value!"); 149 assert(RI->getReturnValue()->getType() == PHI->getType() && 150 "Ret value not consistent in function!"); 151 PHI->addIncoming(RI->getReturnValue(), BB); 152 } 153 154 // Delete the return instruction now 155 BB->getInstList().erase(RI); 156 } 157 158 // Check to see if the PHI node only has one argument. This is a common 159 // case resulting from there only being a single return instruction in the 160 // function call. Because this is so common, eliminate the PHI node. 161 // 162 if (PHI && PHI->getNumIncomingValues() == 1) { 163 PHI->replaceAllUsesWith(PHI->getIncomingValue(0)); 164 PHI->getParent()->getInstList().erase(PHI); 165 } 166 167 // Change the branch that used to go to AfterCallBB to branch to the first 168 // basic block of the inlined function. 169 // 170 TerminatorInst *Br = OrigBB->getTerminator(); 171 assert(Br && Br->getOpcode() == Instruction::Br && 172 "splitBasicBlock broken!"); 173 Br->setOperand(0, ++LastBlock); 174 175 // If there are any alloca instructions in the block that used to be the entry 176 // block for the callee, move them to the entry block of the caller. First 177 // calculate which instruction they should be inserted before. We insert the 178 // instructions at the end of the current alloca list. 179 // 180 if (isa<AllocaInst>(LastBlock->begin())) { 181 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 182 while (isa<AllocaInst>(InsertPoint)) ++InsertPoint; 183 184 for (BasicBlock::iterator I = LastBlock->begin(), E = LastBlock->end(); 185 I != E; ) 186 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) 187 if (isa<Constant>(AI->getArraySize())) { 188 LastBlock->getInstList().remove(AI); 189 Caller->front().getInstList().insert(InsertPoint, AI); 190 } 191 } 192 193 // If we just inlined a call due to an invoke instruction, scan the inlined 194 // function checking for function calls that should now be made into invoke 195 // instructions, and for unwind's which should be turned into branches. 196 if (InvokeDest) { 197 for (Function::iterator BB = LastBlock, E = Caller->end(); BB != E; ++BB) { 198 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) { 199 // We only need to check for function calls: inlined invoke instructions 200 // require no special handling... 201 if (CallInst *CI = dyn_cast<CallInst>(I)) { 202 // Convert this function call into an invoke instruction... 203 204 // First, split the basic block... 205 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); 206 207 // Next, create the new invoke instruction, inserting it at the end 208 // of the old basic block. 209 InvokeInst *II = 210 new InvokeInst(CI->getCalledValue(), Split, InvokeDest, 211 std::vector<Value*>(CI->op_begin()+1, CI->op_end()), 212 CI->getName(), BB->getTerminator()); 213 214 // Make sure that anything using the call now uses the invoke! 215 CI->replaceAllUsesWith(II); 216 217 // Delete the unconditional branch inserted by splitBasicBlock 218 BB->getInstList().pop_back(); 219 Split->getInstList().pop_front(); // Delete the original call 220 221 // Update any PHI nodes in the exceptional block to indicate that 222 // there is now a new entry in them. 223 unsigned i = 0; 224 for (BasicBlock::iterator I = InvokeDest->begin(); 225 PHINode *PN = dyn_cast<PHINode>(I); ++I, ++i) 226 PN->addIncoming(InvokeDestPHIValues[i], BB); 227 228 // This basic block is now complete, start scanning the next one. 229 break; 230 } else { 231 ++I; 232 } 233 } 234 235 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 236 // An UnwindInst requires special handling when it gets inlined into an 237 // invoke site. Once this happens, we know that the unwind would cause 238 // a control transfer to the invoke exception destination, so we can 239 // transform it into a direct branch to the exception destination. 240 new BranchInst(InvokeDest, UI); 241 242 // Delete the unwind instruction! 243 UI->getParent()->getInstList().pop_back(); 244 245 // Update any PHI nodes in the exceptional block to indicate that 246 // there is now a new entry in them. 247 unsigned i = 0; 248 for (BasicBlock::iterator I = InvokeDest->begin(); 249 PHINode *PN = dyn_cast<PHINode>(I); ++I, ++i) 250 PN->addIncoming(InvokeDestPHIValues[i], BB); 251 } 252 } 253 254 // Now that everything is happy, we have one final detail. The PHI nodes in 255 // the exception destination block still have entries due to the original 256 // invoke instruction. Eliminate these entries (which might even delete the 257 // PHI node) now. 258 for (BasicBlock::iterator I = InvokeDest->begin(); 259 PHINode *PN = dyn_cast<PHINode>(I); ++I) 260 PN->removeIncomingValue(AfterCallBB); 261 } 262 // Now that the function is correct, make it a little bit nicer. In 263 // particular, move the basic blocks inserted from the end of the function 264 // into the space made by splitting the source basic block. 265 // 266 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 267 LastBlock, Caller->end()); 268 269 // We should always be able to fold the entry block of the function into the 270 // single predecessor of the block... 271 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 272 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 273 SimplifyCFG(CalleeEntry); 274 275 // Okay, continue the CFG cleanup. It's often the case that there is only a 276 // single return instruction in the callee function. If this is the case, 277 // then we have an unconditional branch from the return block to the 278 // 'AfterCallBB'. Check for this case, and eliminate the branch is possible. 279 SimplifyCFG(AfterCallBB); 280 return true; 281} 282