1 //===- InlineFunction.cpp - Code to perform function inlining -------------===//
3 // The LLVM Compiler Infrastructure
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.
8 //===----------------------------------------------------------------------===//
10 // This file implements inlining of a function into a call site, resolving
11 // parameters and the return value as appropriate.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/Utils/Cloning.h"
16 #include "llvm/Constants.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/Module.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Intrinsics.h"
21 #include "llvm/Analysis/CallGraph.h"
22 #include "llvm/ADT/SmallVector.h"
23 #include "llvm/Support/CallSite.h"
26 bool llvm::InlineFunction(CallInst *CI, CallGraph *CG, const TargetData *TD) {
27 return InlineFunction(CallSite(CI), CG, TD);
29 bool llvm::InlineFunction(InvokeInst *II, CallGraph *CG, const TargetData *TD) {
30 return InlineFunction(CallSite(II), CG, TD);
33 /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls
34 /// in the body of the inlined function into invokes and turn unwind
35 /// instructions into branches to the invoke unwind dest.
37 /// II is the invoke instruction begin inlined. FirstNewBlock is the first
38 /// block of the inlined code (the last block is the end of the function),
39 /// and InlineCodeInfo is information about the code that got inlined.
40 static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
41 ClonedCodeInfo &InlinedCodeInfo) {
42 BasicBlock *InvokeDest = II->getUnwindDest();
43 std::vector<Value*> InvokeDestPHIValues;
45 // If there are PHI nodes in the unwind destination block, we need to
46 // keep track of which values came into them from this invoke, then remove
47 // the entry for this block.
48 BasicBlock *InvokeBlock = II->getParent();
49 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) {
50 PHINode *PN = cast<PHINode>(I);
51 // Save the value to use for this edge.
52 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock));
55 Function *Caller = FirstNewBlock->getParent();
57 // The inlined code is currently at the end of the function, scan from the
58 // start of the inlined code to its end, checking for stuff we need to
60 if (InlinedCodeInfo.ContainsCalls || InlinedCodeInfo.ContainsUnwinds) {
61 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
63 if (InlinedCodeInfo.ContainsCalls) {
64 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ){
65 Instruction *I = BBI++;
67 // We only need to check for function calls: inlined invoke
68 // instructions require no special handling.
69 if (!isa<CallInst>(I)) continue;
70 CallInst *CI = cast<CallInst>(I);
72 // If this is an intrinsic function call or an inline asm, don't
73 // convert it to an invoke.
74 if ((CI->getCalledFunction() &&
75 CI->getCalledFunction()->getIntrinsicID()) ||
76 isa<InlineAsm>(CI->getCalledValue()))
79 // Convert this function call into an invoke instruction.
80 // First, split the basic block.
81 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");
83 // Next, create the new invoke instruction, inserting it at the end
84 // of the old basic block.
85 SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end());
87 new InvokeInst(CI->getCalledValue(), Split, InvokeDest,
88 InvokeArgs.begin(), InvokeArgs.end(),
89 CI->getName(), BB->getTerminator());
90 II->setCallingConv(CI->getCallingConv());
91 II->setParamAttrs(CI->getParamAttrs());
93 // Make sure that anything using the call now uses the invoke!
94 CI->replaceAllUsesWith(II);
96 // Delete the unconditional branch inserted by splitBasicBlock
97 BB->getInstList().pop_back();
98 Split->getInstList().pop_front(); // Delete the original call
100 // Update any PHI nodes in the exceptional block to indicate that
101 // there is now a new entry in them.
103 for (BasicBlock::iterator I = InvokeDest->begin();
104 isa<PHINode>(I); ++I, ++i) {
105 PHINode *PN = cast<PHINode>(I);
106 PN->addIncoming(InvokeDestPHIValues[i], BB);
109 // This basic block is now complete, start scanning the next one.
114 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
115 // An UnwindInst requires special handling when it gets inlined into an
116 // invoke site. Once this happens, we know that the unwind would cause
117 // a control transfer to the invoke exception destination, so we can
118 // transform it into a direct branch to the exception destination.
119 new BranchInst(InvokeDest, UI);
121 // Delete the unwind instruction!
122 UI->getParent()->getInstList().pop_back();
124 // Update any PHI nodes in the exceptional block to indicate that
125 // there is now a new entry in them.
127 for (BasicBlock::iterator I = InvokeDest->begin();
128 isa<PHINode>(I); ++I, ++i) {
129 PHINode *PN = cast<PHINode>(I);
130 PN->addIncoming(InvokeDestPHIValues[i], BB);
136 // Now that everything is happy, we have one final detail. The PHI nodes in
137 // the exception destination block still have entries due to the original
138 // invoke instruction. Eliminate these entries (which might even delete the
140 InvokeDest->removePredecessor(II->getParent());
143 /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee
144 /// into the caller, update the specified callgraph to reflect the changes we
145 /// made. Note that it's possible that not all code was copied over, so only
146 /// some edges of the callgraph will be remain.
147 static void UpdateCallGraphAfterInlining(const Function *Caller,
148 const Function *Callee,
149 Function::iterator FirstNewBlock,
150 DenseMap<const Value*, Value*> &ValueMap,
152 // Update the call graph by deleting the edge from Callee to Caller
153 CallGraphNode *CalleeNode = CG[Callee];
154 CallGraphNode *CallerNode = CG[Caller];
155 CallerNode->removeCallEdgeTo(CalleeNode);
157 // Since we inlined some uninlined call sites in the callee into the caller,
158 // add edges from the caller to all of the callees of the callee.
159 for (CallGraphNode::iterator I = CalleeNode->begin(),
160 E = CalleeNode->end(); I != E; ++I) {
161 const Instruction *OrigCall = I->first.getInstruction();
163 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall);
164 // Only copy the edge if the call was inlined!
165 if (VMI != ValueMap.end() && VMI->second) {
166 // If the call was inlined, but then constant folded, there is no edge to
167 // add. Check for this case.
168 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second))
169 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second);
175 // InlineFunction - This function inlines the called function into the basic
176 // block of the caller. This returns false if it is not possible to inline this
177 // call. The program is still in a well defined state if this occurs though.
179 // Note that this only does one level of inlining. For example, if the
180 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
181 // exists in the instruction stream. Similiarly this will inline a recursive
182 // function by one level.
184 bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) {
185 Instruction *TheCall = CS.getInstruction();
186 assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
187 "Instruction not in function!");
189 const Function *CalledFunc = CS.getCalledFunction();
190 if (CalledFunc == 0 || // Can't inline external function or indirect
191 CalledFunc->isDeclaration() || // call, or call to a vararg function!
192 CalledFunc->getFunctionType()->isVarArg()) return false;
195 // If the call to the callee is a non-tail call, we must clear the 'tail'
196 // flags on any calls that we inline.
197 bool MustClearTailCallFlags =
198 isa<CallInst>(TheCall) && !cast<CallInst>(TheCall)->isTailCall();
200 BasicBlock *OrigBB = TheCall->getParent();
201 Function *Caller = OrigBB->getParent();
203 // Get an iterator to the last basic block in the function, which will have
204 // the new function inlined after it.
206 Function::iterator LastBlock = &Caller->back();
208 // Make sure to capture all of the return instructions from the cloned
210 std::vector<ReturnInst*> Returns;
211 ClonedCodeInfo InlinedFunctionInfo;
212 Function::iterator FirstNewBlock;
214 { // Scope to destroy ValueMap after cloning.
215 DenseMap<const Value*, Value*> ValueMap;
217 // Calculate the vector of arguments to pass into the function cloner, which
218 // matches up the formal to the actual argument values.
219 assert(std::distance(CalledFunc->arg_begin(), CalledFunc->arg_end()) ==
220 std::distance(CS.arg_begin(), CS.arg_end()) &&
221 "No varargs calls can be inlined!");
222 CallSite::arg_iterator AI = CS.arg_begin();
223 for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
224 E = CalledFunc->arg_end(); I != E; ++I, ++AI)
227 // We want the inliner to prune the code as it copies. We would LOVE to
228 // have no dead or constant instructions leftover after inlining occurs
229 // (which can happen, e.g., because an argument was constant), but we'll be
230 // happy with whatever the cloner can do.
231 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i",
232 &InlinedFunctionInfo, TD);
234 // Remember the first block that is newly cloned over.
235 FirstNewBlock = LastBlock; ++FirstNewBlock;
237 // Update the callgraph if requested.
239 UpdateCallGraphAfterInlining(Caller, CalledFunc, FirstNewBlock, ValueMap,
243 // If there are any alloca instructions in the block that used to be the entry
244 // block for the callee, move them to the entry block of the caller. First
245 // calculate which instruction they should be inserted before. We insert the
246 // instructions at the end of the current alloca list.
249 BasicBlock::iterator InsertPoint = Caller->begin()->begin();
250 for (BasicBlock::iterator I = FirstNewBlock->begin(),
251 E = FirstNewBlock->end(); I != E; )
252 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) {
253 // If the alloca is now dead, remove it. This often occurs due to code
255 if (AI->use_empty()) {
256 AI->eraseFromParent();
260 if (isa<Constant>(AI->getArraySize())) {
261 // Scan for the block of allocas that we can move over, and move them
263 while (isa<AllocaInst>(I) &&
264 isa<Constant>(cast<AllocaInst>(I)->getArraySize()))
267 // Transfer all of the allocas over in a block. Using splice means
268 // that the instructions aren't removed from the symbol table, then
270 Caller->getEntryBlock().getInstList().splice(
272 FirstNewBlock->getInstList(),
278 // If the inlined code contained dynamic alloca instructions, wrap the inlined
279 // code with llvm.stacksave/llvm.stackrestore intrinsics.
280 if (InlinedFunctionInfo.ContainsDynamicAllocas) {
281 Module *M = Caller->getParent();
282 const Type *BytePtr = PointerType::get(Type::Int8Ty);
283 // Get the two intrinsics we care about.
284 Constant *StackSave, *StackRestore;
285 StackSave = M->getOrInsertFunction("llvm.stacksave", BytePtr, NULL);
286 StackRestore = M->getOrInsertFunction("llvm.stackrestore", Type::VoidTy,
289 // If we are preserving the callgraph, add edges to the stacksave/restore
290 // functions for the calls we insert.
291 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0;
293 // We know that StackSave/StackRestore are Function*'s, because they are
294 // intrinsics which must have the right types.
295 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave));
296 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore));
297 CallerNode = (*CG)[Caller];
300 // Insert the llvm.stacksave.
301 CallInst *SavedPtr = new CallInst(StackSave, "savedstack",
302 FirstNewBlock->begin());
303 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN);
305 // Insert a call to llvm.stackrestore before any return instructions in the
307 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
308 CallInst *CI = new CallInst(StackRestore, SavedPtr, "", Returns[i]);
309 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
312 // Count the number of StackRestore calls we insert.
313 unsigned NumStackRestores = Returns.size();
315 // If we are inlining an invoke instruction, insert restores before each
316 // unwind. These unwinds will be rewritten into branches later.
317 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) {
318 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
320 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
321 new CallInst(StackRestore, SavedPtr, "", UI);
327 // If we are inlining tail call instruction through a call site that isn't
328 // marked 'tail', we must remove the tail marker for any calls in the inlined
330 if (MustClearTailCallFlags && InlinedFunctionInfo.ContainsCalls) {
331 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
333 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
334 if (CallInst *CI = dyn_cast<CallInst>(I))
335 CI->setTailCall(false);
338 // If we are inlining for an invoke instruction, we must make sure to rewrite
339 // any inlined 'unwind' instructions into branches to the invoke exception
340 // destination, and call instructions into invoke instructions.
341 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
342 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);
344 // If we cloned in _exactly one_ basic block, and if that block ends in a
345 // return instruction, we splice the body of the inlined callee directly into
346 // the calling basic block.
347 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
348 // Move all of the instructions right before the call.
349 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
350 FirstNewBlock->begin(), FirstNewBlock->end());
351 // Remove the cloned basic block.
352 Caller->getBasicBlockList().pop_back();
354 // If the call site was an invoke instruction, add a branch to the normal
356 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
357 new BranchInst(II->getNormalDest(), TheCall);
359 // If the return instruction returned a value, replace uses of the call with
360 // uses of the returned value.
361 if (!TheCall->use_empty())
362 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
364 // Since we are now done with the Call/Invoke, we can delete it.
365 TheCall->getParent()->getInstList().erase(TheCall);
367 // Since we are now done with the return instruction, delete it also.
368 Returns[0]->getParent()->getInstList().erase(Returns[0]);
370 // We are now done with the inlining.
374 // Otherwise, we have the normal case, of more than one block to inline or
375 // multiple return sites.
377 // We want to clone the entire callee function into the hole between the
378 // "starter" and "ender" blocks. How we accomplish this depends on whether
379 // this is an invoke instruction or a call instruction.
380 BasicBlock *AfterCallBB;
381 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
383 // Add an unconditional branch to make this look like the CallInst case...
384 BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall);
386 // Split the basic block. This guarantees that no PHI nodes will have to be
387 // updated due to new incoming edges, and make the invoke case more
388 // symmetric to the call case.
389 AfterCallBB = OrigBB->splitBasicBlock(NewBr,
390 CalledFunc->getName()+".exit");
392 } else { // It's a call
393 // If this is a call instruction, we need to split the basic block that
394 // the call lives in.
396 AfterCallBB = OrigBB->splitBasicBlock(TheCall,
397 CalledFunc->getName()+".exit");
400 // Change the branch that used to go to AfterCallBB to branch to the first
401 // basic block of the inlined function.
403 TerminatorInst *Br = OrigBB->getTerminator();
404 assert(Br && Br->getOpcode() == Instruction::Br &&
405 "splitBasicBlock broken!");
406 Br->setOperand(0, FirstNewBlock);
409 // Now that the function is correct, make it a little bit nicer. In
410 // particular, move the basic blocks inserted from the end of the function
411 // into the space made by splitting the source basic block.
413 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
414 FirstNewBlock, Caller->end());
416 // Handle all of the return instructions that we just cloned in, and eliminate
417 // any users of the original call/invoke instruction.
418 if (Returns.size() > 1) {
419 // The PHI node should go at the front of the new basic block to merge all
420 // possible incoming values.
423 if (!TheCall->use_empty()) {
424 PHI = new PHINode(CalledFunc->getReturnType(),
425 TheCall->getName(), AfterCallBB->begin());
427 // Anything that used the result of the function call should now use the
428 // PHI node as their operand.
430 TheCall->replaceAllUsesWith(PHI);
433 // Loop over all of the return instructions, turning them into unconditional
434 // branches to the merge point now, and adding entries to the PHI node as
436 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
437 ReturnInst *RI = Returns[i];
440 assert(RI->getReturnValue() && "Ret should have value!");
441 assert(RI->getReturnValue()->getType() == PHI->getType() &&
442 "Ret value not consistent in function!");
443 PHI->addIncoming(RI->getReturnValue(), RI->getParent());
446 // Add a branch to the merge point where the PHI node lives if it exists.
447 new BranchInst(AfterCallBB, RI);
449 // Delete the return instruction now
450 RI->getParent()->getInstList().erase(RI);
453 } else if (!Returns.empty()) {
454 // Otherwise, if there is exactly one return value, just replace anything
455 // using the return value of the call with the computed value.
456 if (!TheCall->use_empty())
457 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
459 // Splice the code from the return block into the block that it will return
460 // to, which contains the code that was after the call.
461 BasicBlock *ReturnBB = Returns[0]->getParent();
462 AfterCallBB->getInstList().splice(AfterCallBB->begin(),
463 ReturnBB->getInstList());
465 // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
466 ReturnBB->replaceAllUsesWith(AfterCallBB);
468 // Delete the return instruction now and empty ReturnBB now.
469 Returns[0]->eraseFromParent();
470 ReturnBB->eraseFromParent();
471 } else if (!TheCall->use_empty()) {
472 // No returns, but something is using the return value of the call. Just
474 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
477 // Since we are now done with the Call/Invoke, we can delete it.
478 TheCall->eraseFromParent();
480 // We should always be able to fold the entry block of the function into the
481 // single predecessor of the block...
482 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
483 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
485 // Splice the code entry block into calling block, right before the
486 // unconditional branch.
487 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
488 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes
490 // Remove the unconditional branch.
491 OrigBB->getInstList().erase(Br);
493 // Now we can remove the CalleeEntry block, which is now empty.
494 Caller->getBasicBlockList().erase(CalleeEntry);