LLVM API Documentation
00001 //===- InlineFunction.cpp - Code to perform function inlining -------------===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file implements inlining of a function into a call site, resolving 00011 // parameters and the return value as appropriate. 00012 // 00013 //===----------------------------------------------------------------------===// 00014 00015 #include "llvm/Transforms/Utils/Cloning.h" 00016 #include "llvm/Constants.h" 00017 #include "llvm/DerivedTypes.h" 00018 #include "llvm/Module.h" 00019 #include "llvm/Instructions.h" 00020 #include "llvm/Intrinsics.h" 00021 #include "llvm/Analysis/CallGraph.h" 00022 #include "llvm/Support/CallSite.h" 00023 using namespace llvm; 00024 00025 bool llvm::InlineFunction(CallInst *CI, CallGraph *CG) { 00026 return InlineFunction(CallSite(CI), CG); 00027 } 00028 bool llvm::InlineFunction(InvokeInst *II, CallGraph *CG) { 00029 return InlineFunction(CallSite(II), CG); 00030 } 00031 00032 /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls 00033 /// in the body of the inlined function into invokes and turn unwind 00034 /// instructions into branches to the invoke unwind dest. 00035 /// 00036 /// II is the invoke instruction begin inlined. FirstNewBlock is the first 00037 /// block of the inlined code (the last block is the end of the function), 00038 /// and InlineCodeInfo is information about the code that got inlined. 00039 static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock, 00040 ClonedCodeInfo &InlinedCodeInfo) { 00041 BasicBlock *InvokeDest = II->getUnwindDest(); 00042 std::vector<Value*> InvokeDestPHIValues; 00043 00044 // If there are PHI nodes in the unwind destination block, we need to 00045 // keep track of which values came into them from this invoke, then remove 00046 // the entry for this block. 00047 BasicBlock *InvokeBlock = II->getParent(); 00048 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) { 00049 PHINode *PN = cast<PHINode>(I); 00050 // Save the value to use for this edge. 00051 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock)); 00052 } 00053 00054 Function *Caller = FirstNewBlock->getParent(); 00055 00056 // The inlined code is currently at the end of the function, scan from the 00057 // start of the inlined code to its end, checking for stuff we need to 00058 // rewrite. 00059 if (InlinedCodeInfo.ContainsCalls || InlinedCodeInfo.ContainsUnwinds) { 00060 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 00061 BB != E; ++BB) { 00062 if (InlinedCodeInfo.ContainsCalls) { 00063 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ){ 00064 Instruction *I = BBI++; 00065 00066 // We only need to check for function calls: inlined invoke 00067 // instructions require no special handling. 00068 if (!isa<CallInst>(I)) continue; 00069 CallInst *CI = cast<CallInst>(I); 00070 00071 // If this is an intrinsic function call, don't convert it to an 00072 // invoke. 00073 if (CI->getCalledFunction() && 00074 CI->getCalledFunction()->getIntrinsicID()) 00075 continue; 00076 00077 // Convert this function call into an invoke instruction. 00078 // First, split the basic block. 00079 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); 00080 00081 // Next, create the new invoke instruction, inserting it at the end 00082 // of the old basic block. 00083 InvokeInst *II = 00084 new InvokeInst(CI->getCalledValue(), Split, InvokeDest, 00085 std::vector<Value*>(CI->op_begin()+1, CI->op_end()), 00086 CI->getName(), BB->getTerminator()); 00087 II->setCallingConv(CI->getCallingConv()); 00088 00089 // Make sure that anything using the call now uses the invoke! 00090 CI->replaceAllUsesWith(II); 00091 00092 // Delete the unconditional branch inserted by splitBasicBlock 00093 BB->getInstList().pop_back(); 00094 Split->getInstList().pop_front(); // Delete the original call 00095 00096 // Update any PHI nodes in the exceptional block to indicate that 00097 // there is now a new entry in them. 00098 unsigned i = 0; 00099 for (BasicBlock::iterator I = InvokeDest->begin(); 00100 isa<PHINode>(I); ++I, ++i) { 00101 PHINode *PN = cast<PHINode>(I); 00102 PN->addIncoming(InvokeDestPHIValues[i], BB); 00103 } 00104 00105 // This basic block is now complete, start scanning the next one. 00106 break; 00107 } 00108 } 00109 00110 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 00111 // An UnwindInst requires special handling when it gets inlined into an 00112 // invoke site. Once this happens, we know that the unwind would cause 00113 // a control transfer to the invoke exception destination, so we can 00114 // transform it into a direct branch to the exception destination. 00115 new BranchInst(InvokeDest, UI); 00116 00117 // Delete the unwind instruction! 00118 UI->getParent()->getInstList().pop_back(); 00119 00120 // Update any PHI nodes in the exceptional block to indicate that 00121 // there is now a new entry in them. 00122 unsigned i = 0; 00123 for (BasicBlock::iterator I = InvokeDest->begin(); 00124 isa<PHINode>(I); ++I, ++i) { 00125 PHINode *PN = cast<PHINode>(I); 00126 PN->addIncoming(InvokeDestPHIValues[i], BB); 00127 } 00128 } 00129 } 00130 } 00131 00132 // Now that everything is happy, we have one final detail. The PHI nodes in 00133 // the exception destination block still have entries due to the original 00134 // invoke instruction. Eliminate these entries (which might even delete the 00135 // PHI node) now. 00136 InvokeDest->removePredecessor(II->getParent()); 00137 } 00138 00139 /// UpdateCallGraphAfterInlining - Once we have finished inlining a call from 00140 /// caller to callee, update the specified callgraph to reflect the changes we 00141 /// made. 00142 static void UpdateCallGraphAfterInlining(const Function *Caller, 00143 const Function *Callee, 00144 CallGraph &CG) { 00145 // Update the call graph by deleting the edge from Callee to Caller 00146 CallGraphNode *CalleeNode = CG[Callee]; 00147 CallGraphNode *CallerNode = CG[Caller]; 00148 CallerNode->removeCallEdgeTo(CalleeNode); 00149 00150 // Since we inlined all uninlined call sites in the callee into the caller, 00151 // add edges from the caller to all of the callees of the callee. 00152 for (CallGraphNode::iterator I = CalleeNode->begin(), 00153 E = CalleeNode->end(); I != E; ++I) 00154 CallerNode->addCalledFunction(*I); 00155 } 00156 00157 00158 // InlineFunction - This function inlines the called function into the basic 00159 // block of the caller. This returns false if it is not possible to inline this 00160 // call. The program is still in a well defined state if this occurs though. 00161 // 00162 // Note that this only does one level of inlining. For example, if the 00163 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 00164 // exists in the instruction stream. Similiarly this will inline a recursive 00165 // function by one level. 00166 // 00167 bool llvm::InlineFunction(CallSite CS, CallGraph *CG) { 00168 Instruction *TheCall = CS.getInstruction(); 00169 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 00170 "Instruction not in function!"); 00171 00172 const Function *CalledFunc = CS.getCalledFunction(); 00173 if (CalledFunc == 0 || // Can't inline external function or indirect 00174 CalledFunc->isExternal() || // call, or call to a vararg function! 00175 CalledFunc->getFunctionType()->isVarArg()) return false; 00176 00177 00178 // If the call to the callee is a non-tail call, we must clear the 'tail' 00179 // flags on any calls that we inline. 00180 bool MustClearTailCallFlags = 00181 isa<CallInst>(TheCall) && !cast<CallInst>(TheCall)->isTailCall(); 00182 00183 BasicBlock *OrigBB = TheCall->getParent(); 00184 Function *Caller = OrigBB->getParent(); 00185 00186 // Get an iterator to the last basic block in the function, which will have 00187 // the new function inlined after it. 00188 // 00189 Function::iterator LastBlock = &Caller->back(); 00190 00191 // Make sure to capture all of the return instructions from the cloned 00192 // function. 00193 std::vector<ReturnInst*> Returns; 00194 ClonedCodeInfo InlinedFunctionInfo; 00195 { // Scope to destroy ValueMap after cloning. 00196 // Calculate the vector of arguments to pass into the function cloner... 00197 std::map<const Value*, Value*> ValueMap; 00198 assert(std::distance(CalledFunc->arg_begin(), CalledFunc->arg_end()) == 00199 std::distance(CS.arg_begin(), CS.arg_end()) && 00200 "No varargs calls can be inlined!"); 00201 00202 CallSite::arg_iterator AI = CS.arg_begin(); 00203 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 00204 E = CalledFunc->arg_end(); I != E; ++I, ++AI) 00205 ValueMap[I] = *AI; 00206 00207 // Clone the entire body of the callee into the caller. 00208 CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 00209 &InlinedFunctionInfo); 00210 } 00211 00212 // Remember the first block that is newly cloned over. 00213 Function::iterator FirstNewBlock = LastBlock; ++FirstNewBlock; 00214 00215 // If there are any alloca instructions in the block that used to be the entry 00216 // block for the callee, move them to the entry block of the caller. First 00217 // calculate which instruction they should be inserted before. We insert the 00218 // instructions at the end of the current alloca list. 00219 // 00220 { 00221 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 00222 for (BasicBlock::iterator I = FirstNewBlock->begin(), 00223 E = FirstNewBlock->end(); I != E; ) 00224 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) 00225 if (isa<Constant>(AI->getArraySize())) { 00226 // Scan for the block of allocas that we can move over, and move them 00227 // all at once. 00228 while (isa<AllocaInst>(I) && 00229 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 00230 ++I; 00231 00232 // Transfer all of the allocas over in a block. Using splice means 00233 // that they instructions aren't removed from the symbol table, then 00234 // reinserted. 00235 Caller->front().getInstList().splice(InsertPoint, 00236 FirstNewBlock->getInstList(), 00237 AI, I); 00238 } 00239 } 00240 00241 // If the inlined code contained dynamic alloca instructions, wrap the inlined 00242 // code with llvm.stacksave/llvm.stackrestore intrinsics. 00243 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 00244 Module *M = Caller->getParent(); 00245 const Type *SBytePtr = PointerType::get(Type::SByteTy); 00246 // Get the two intrinsics we care about. 00247 Function *StackSave, *StackRestore; 00248 StackSave = M->getOrInsertFunction("llvm.stacksave", SBytePtr, NULL); 00249 StackRestore = M->getOrInsertFunction("llvm.stackrestore", Type::VoidTy, 00250 SBytePtr, NULL); 00251 00252 // Insert the llvm.stacksave. 00253 Value *SavedPtr = new CallInst(StackSave, "savedstack", 00254 FirstNewBlock->begin()); 00255 00256 // Insert a call to llvm.stackrestore before any return instructions in the 00257 // inlined function. 00258 for (unsigned i = 0, e = Returns.size(); i != e; ++i) 00259 new CallInst(StackRestore, SavedPtr, "", Returns[i]); 00260 00261 // Count the number of StackRestore calls we insert. 00262 unsigned NumStackRestores = Returns.size(); 00263 00264 // If we are inlining an invoke instruction, insert restores before each 00265 // unwind. These unwinds will be rewritten into branches later. 00266 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 00267 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 00268 BB != E; ++BB) 00269 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 00270 new CallInst(StackRestore, SavedPtr, "", UI); 00271 ++NumStackRestores; 00272 } 00273 } 00274 00275 // If we are supposed to update the callgraph, do so now. 00276 if (CG) { 00277 CallGraphNode *StackSaveCGN = CG->getOrInsertFunction(StackSave); 00278 CallGraphNode *StackRestoreCGN = CG->getOrInsertFunction(StackRestore); 00279 CallGraphNode *CallerNode = (*CG)[Caller]; 00280 00281 // 'Caller' now calls llvm.stacksave one more time. 00282 CallerNode->addCalledFunction(StackSaveCGN); 00283 00284 // 'Caller' now calls llvm.stackrestore the appropriate number of times. 00285 for (unsigned i = 0; i != NumStackRestores; ++i) 00286 CallerNode->addCalledFunction(StackRestoreCGN); 00287 } 00288 } 00289 00290 // If we are inlining tail call instruction through a call site that isn't 00291 // marked 'tail', we must remove the tail marker for any calls in the inlined 00292 // code. 00293 if (MustClearTailCallFlags && InlinedFunctionInfo.ContainsCalls) { 00294 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 00295 BB != E; ++BB) 00296 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 00297 if (CallInst *CI = dyn_cast<CallInst>(I)) 00298 CI->setTailCall(false); 00299 } 00300 00301 // If we are inlining for an invoke instruction, we must make sure to rewrite 00302 // any inlined 'unwind' instructions into branches to the invoke exception 00303 // destination, and call instructions into invoke instructions. 00304 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 00305 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 00306 00307 // If we cloned in _exactly one_ basic block, and if that block ends in a 00308 // return instruction, we splice the body of the inlined callee directly into 00309 // the calling basic block. 00310 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 00311 // Move all of the instructions right before the call. 00312 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 00313 FirstNewBlock->begin(), FirstNewBlock->end()); 00314 // Remove the cloned basic block. 00315 Caller->getBasicBlockList().pop_back(); 00316 00317 // If the call site was an invoke instruction, add a branch to the normal 00318 // destination. 00319 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 00320 new BranchInst(II->getNormalDest(), TheCall); 00321 00322 // If the return instruction returned a value, replace uses of the call with 00323 // uses of the returned value. 00324 if (!TheCall->use_empty()) 00325 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 00326 00327 // Since we are now done with the Call/Invoke, we can delete it. 00328 TheCall->getParent()->getInstList().erase(TheCall); 00329 00330 // Since we are now done with the return instruction, delete it also. 00331 Returns[0]->getParent()->getInstList().erase(Returns[0]); 00332 00333 // Update the callgraph if requested. 00334 if (CG) UpdateCallGraphAfterInlining(Caller, CalledFunc, *CG); 00335 00336 // We are now done with the inlining. 00337 return true; 00338 } 00339 00340 // Otherwise, we have the normal case, of more than one block to inline or 00341 // multiple return sites. 00342 00343 // We want to clone the entire callee function into the hole between the 00344 // "starter" and "ender" blocks. How we accomplish this depends on whether 00345 // this is an invoke instruction or a call instruction. 00346 BasicBlock *AfterCallBB; 00347 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 00348 00349 // Add an unconditional branch to make this look like the CallInst case... 00350 BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall); 00351 00352 // Split the basic block. This guarantees that no PHI nodes will have to be 00353 // updated due to new incoming edges, and make the invoke case more 00354 // symmetric to the call case. 00355 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 00356 CalledFunc->getName()+".exit"); 00357 00358 } else { // It's a call 00359 // If this is a call instruction, we need to split the basic block that 00360 // the call lives in. 00361 // 00362 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 00363 CalledFunc->getName()+".exit"); 00364 } 00365 00366 // Change the branch that used to go to AfterCallBB to branch to the first 00367 // basic block of the inlined function. 00368 // 00369 TerminatorInst *Br = OrigBB->getTerminator(); 00370 assert(Br && Br->getOpcode() == Instruction::Br && 00371 "splitBasicBlock broken!"); 00372 Br->setOperand(0, FirstNewBlock); 00373 00374 00375 // Now that the function is correct, make it a little bit nicer. In 00376 // particular, move the basic blocks inserted from the end of the function 00377 // into the space made by splitting the source basic block. 00378 // 00379 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 00380 FirstNewBlock, Caller->end()); 00381 00382 // Handle all of the return instructions that we just cloned in, and eliminate 00383 // any users of the original call/invoke instruction. 00384 if (Returns.size() > 1) { 00385 // The PHI node should go at the front of the new basic block to merge all 00386 // possible incoming values. 00387 // 00388 PHINode *PHI = 0; 00389 if (!TheCall->use_empty()) { 00390 PHI = new PHINode(CalledFunc->getReturnType(), 00391 TheCall->getName(), AfterCallBB->begin()); 00392 00393 // Anything that used the result of the function call should now use the 00394 // PHI node as their operand. 00395 // 00396 TheCall->replaceAllUsesWith(PHI); 00397 } 00398 00399 // Loop over all of the return instructions, turning them into unconditional 00400 // branches to the merge point now, and adding entries to the PHI node as 00401 // appropriate. 00402 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 00403 ReturnInst *RI = Returns[i]; 00404 00405 if (PHI) { 00406 assert(RI->getReturnValue() && "Ret should have value!"); 00407 assert(RI->getReturnValue()->getType() == PHI->getType() && 00408 "Ret value not consistent in function!"); 00409 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 00410 } 00411 00412 // Add a branch to the merge point where the PHI node lives if it exists. 00413 new BranchInst(AfterCallBB, RI); 00414 00415 // Delete the return instruction now 00416 RI->getParent()->getInstList().erase(RI); 00417 } 00418 00419 } else if (!Returns.empty()) { 00420 // Otherwise, if there is exactly one return value, just replace anything 00421 // using the return value of the call with the computed value. 00422 if (!TheCall->use_empty()) 00423 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 00424 00425 // Splice the code from the return block into the block that it will return 00426 // to, which contains the code that was after the call. 00427 BasicBlock *ReturnBB = Returns[0]->getParent(); 00428 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 00429 ReturnBB->getInstList()); 00430 00431 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 00432 ReturnBB->replaceAllUsesWith(AfterCallBB); 00433 00434 // Delete the return instruction now and empty ReturnBB now. 00435 Returns[0]->eraseFromParent(); 00436 ReturnBB->eraseFromParent(); 00437 } else if (!TheCall->use_empty()) { 00438 // No returns, but something is using the return value of the call. Just 00439 // nuke the result. 00440 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 00441 } 00442 00443 // Since we are now done with the Call/Invoke, we can delete it. 00444 TheCall->eraseFromParent(); 00445 00446 // We should always be able to fold the entry block of the function into the 00447 // single predecessor of the block... 00448 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 00449 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 00450 00451 // Splice the code entry block into calling block, right before the 00452 // unconditional branch. 00453 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 00454 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 00455 00456 // Remove the unconditional branch. 00457 OrigBB->getInstList().erase(Br); 00458 00459 // Now we can remove the CalleeEntry block, which is now empty. 00460 Caller->getBasicBlockList().erase(CalleeEntry); 00461 00462 // Update the callgraph if requested. 00463 if (CG) UpdateCallGraphAfterInlining(Caller, CalledFunc, *CG); 00464 00465 return true; 00466 }