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 // FIXME: This pass should transform alloca instructions in the called function
14 // into alloca/dealloca pairs! Or perhaps it should refuse to inline them!
16 //===----------------------------------------------------------------------===//
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"
27 bool llvm::InlineFunction(CallInst *CI) { return InlineFunction(CallSite(CI)); }
28 bool llvm::InlineFunction(InvokeInst *II) {return InlineFunction(CallSite(II));}
30 // InlineFunction - This function inlines the called function into the basic
31 // block of the caller. This returns false if it is not possible to inline this
32 // call. The program is still in a well defined state if this occurs though.
34 // Note that this only does one level of inlining. For example, if the
35 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
36 // exists in the instruction stream. Similiarly this will inline a recursive
37 // function by one level.
39 bool llvm::InlineFunction(CallSite CS) {
40 Instruction *TheCall = CS.getInstruction();
41 assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
42 "Instruction not in function!");
44 const Function *CalledFunc = CS.getCalledFunction();
45 if (CalledFunc == 0 || // Can't inline external function or indirect
46 CalledFunc->isExternal() || // call, or call to a vararg function!
47 CalledFunc->getFunctionType()->isVarArg()) return false;
49 BasicBlock *OrigBB = TheCall->getParent();
50 Function *Caller = OrigBB->getParent();
52 // Get an iterator to the last basic block in the function, which will have
53 // the new function inlined after it.
55 Function::iterator LastBlock = &Caller->back();
57 // Make sure to capture all of the return instructions from the cloned
59 std::vector<ReturnInst*> Returns;
60 { // Scope to destroy ValueMap after cloning.
61 // Calculate the vector of arguments to pass into the function cloner...
62 std::map<const Value*, Value*> ValueMap;
63 assert(std::distance(CalledFunc->abegin(), CalledFunc->aend()) ==
64 std::distance(CS.arg_begin(), CS.arg_end()) &&
65 "No varargs calls can be inlined!");
67 CallSite::arg_iterator AI = CS.arg_begin();
68 for (Function::const_aiterator I = CalledFunc->abegin(),
69 E = CalledFunc->aend(); I != E; ++I, ++AI)
72 // Clone the entire body of the callee into the caller.
73 CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i");
76 // Remember the first block that is newly cloned over.
77 Function::iterator FirstNewBlock = LastBlock; ++FirstNewBlock;
79 // If there are any alloca instructions in the block that used to be the entry
80 // block for the callee, move them to the entry block of the caller. First
81 // calculate which instruction they should be inserted before. We insert the
82 // instructions at the end of the current alloca list.
84 if (isa<AllocaInst>(FirstNewBlock->begin())) {
85 BasicBlock::iterator InsertPoint = Caller->begin()->begin();
86 for (BasicBlock::iterator I = FirstNewBlock->begin(),
87 E = FirstNewBlock->end(); I != E; )
88 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++))
89 if (isa<Constant>(AI->getArraySize())) {
90 // Scan for the block of allocas that we can move over.
91 while (isa<AllocaInst>(I) &&
92 isa<Constant>(cast<AllocaInst>(I)->getArraySize()))
95 // Transfer all of the allocas over in a block. Using splice means
96 // that they instructions aren't removed from the symbol table, then
98 Caller->front().getInstList().splice(InsertPoint,
99 FirstNewBlock->getInstList(),
104 // If we are inlining for an invoke instruction, we must make sure to rewrite
105 // any inlined 'unwind' instructions into branches to the invoke exception
106 // destination, and call instructions into invoke instructions.
107 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
108 BasicBlock *InvokeDest = II->getUnwindDest();
109 std::vector<Value*> InvokeDestPHIValues;
111 // If there are PHI nodes in the exceptional destination block, we need to
112 // keep track of which values came into them from this invoke, then remove
113 // the entry for this block.
114 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) {
115 PHINode *PN = cast<PHINode>(I);
116 // Save the value to use for this edge...
117 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(OrigBB));
120 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
122 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
123 // We only need to check for function calls: inlined invoke instructions
124 // require no special handling...
125 if (CallInst *CI = dyn_cast<CallInst>(I)) {
126 // Convert this function call into an invoke instruction... if it's
127 // not an intrinsic function call (which are known to not throw).
128 if (CI->getCalledFunction() &&
129 CI->getCalledFunction()->getIntrinsicID()) {
132 // First, split the basic block...
133 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");
135 // Next, create the new invoke instruction, inserting it at the end
136 // of the old basic block.
138 new InvokeInst(CI->getCalledValue(), Split, InvokeDest,
139 std::vector<Value*>(CI->op_begin()+1, CI->op_end()),
140 CI->getName(), BB->getTerminator());
142 // Make sure that anything using the call now uses the invoke!
143 CI->replaceAllUsesWith(II);
145 // Delete the unconditional branch inserted by splitBasicBlock
146 BB->getInstList().pop_back();
147 Split->getInstList().pop_front(); // Delete the original call
149 // Update any PHI nodes in the exceptional block to indicate that
150 // there is now a new entry in them.
152 for (BasicBlock::iterator I = InvokeDest->begin();
153 isa<PHINode>(I); ++I, ++i) {
154 PHINode *PN = cast<PHINode>(I);
155 PN->addIncoming(InvokeDestPHIValues[i], BB);
158 // This basic block is now complete, start scanning the next one.
166 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
167 // An UnwindInst requires special handling when it gets inlined into an
168 // invoke site. Once this happens, we know that the unwind would cause
169 // a control transfer to the invoke exception destination, so we can
170 // transform it into a direct branch to the exception destination.
171 new BranchInst(InvokeDest, UI);
173 // Delete the unwind instruction!
174 UI->getParent()->getInstList().pop_back();
176 // Update any PHI nodes in the exceptional block to indicate that
177 // there is now a new entry in them.
179 for (BasicBlock::iterator I = InvokeDest->begin();
180 isa<PHINode>(I); ++I, ++i) {
181 PHINode *PN = cast<PHINode>(I);
182 PN->addIncoming(InvokeDestPHIValues[i], BB);
187 // Now that everything is happy, we have one final detail. The PHI nodes in
188 // the exception destination block still have entries due to the original
189 // invoke instruction. Eliminate these entries (which might even delete the
191 InvokeDest->removePredecessor(II->getParent());
194 // If we cloned in _exactly one_ basic block, and if that block ends in a
195 // return instruction, we splice the body of the inlined callee directly into
196 // the calling basic block.
197 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
198 // Move all of the instructions right before the call.
199 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
200 FirstNewBlock->begin(), FirstNewBlock->end());
201 // Remove the cloned basic block.
202 Caller->getBasicBlockList().pop_back();
204 // If the call site was an invoke instruction, add a branch to the normal
206 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
207 new BranchInst(II->getNormalDest(), TheCall);
209 // If the return instruction returned a value, replace uses of the call with
210 // uses of the returned value.
211 if (!TheCall->use_empty())
212 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
214 // Since we are now done with the Call/Invoke, we can delete it.
215 TheCall->getParent()->getInstList().erase(TheCall);
217 // Since we are now done with the return instruction, delete it also.
218 Returns[0]->getParent()->getInstList().erase(Returns[0]);
220 // We are now done with the inlining.
224 // Otherwise, we have the normal case, of more than one block to inline or
225 // multiple return sites.
227 // We want to clone the entire callee function into the hole between the
228 // "starter" and "ender" blocks. How we accomplish this depends on whether
229 // this is an invoke instruction or a call instruction.
230 BasicBlock *AfterCallBB;
231 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
233 // Add an unconditional branch to make this look like the CallInst case...
234 BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall);
236 // Split the basic block. This guarantees that no PHI nodes will have to be
237 // updated due to new incoming edges, and make the invoke case more
238 // symmetric to the call case.
239 AfterCallBB = OrigBB->splitBasicBlock(NewBr,
240 CalledFunc->getName()+".entry");
242 } else { // It's a call
243 // If this is a call instruction, we need to split the basic block that
244 // the call lives in.
246 AfterCallBB = OrigBB->splitBasicBlock(TheCall,
247 CalledFunc->getName()+".entry");
250 // Change the branch that used to go to AfterCallBB to branch to the first
251 // basic block of the inlined function.
253 TerminatorInst *Br = OrigBB->getTerminator();
254 assert(Br && Br->getOpcode() == Instruction::Br &&
255 "splitBasicBlock broken!");
256 Br->setOperand(0, FirstNewBlock);
259 // Now that the function is correct, make it a little bit nicer. In
260 // particular, move the basic blocks inserted from the end of the function
261 // into the space made by splitting the source basic block.
263 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
264 FirstNewBlock, Caller->end());
266 // Handle all of the return instructions that we just cloned in, and eliminate
267 // any users of the original call/invoke instruction.
268 if (Returns.size() > 1) {
269 // The PHI node should go at the front of the new basic block to merge all
270 // possible incoming values.
273 if (!TheCall->use_empty()) {
274 PHI = new PHINode(CalledFunc->getReturnType(),
275 TheCall->getName(), AfterCallBB->begin());
277 // Anything that used the result of the function call should now use the
278 // PHI node as their operand.
280 TheCall->replaceAllUsesWith(PHI);
283 // Loop over all of the return instructions, turning them into unconditional
284 // branches to the merge point now, and adding entries to the PHI node as
286 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
287 ReturnInst *RI = Returns[i];
290 assert(RI->getReturnValue() && "Ret should have value!");
291 assert(RI->getReturnValue()->getType() == PHI->getType() &&
292 "Ret value not consistent in function!");
293 PHI->addIncoming(RI->getReturnValue(), RI->getParent());
296 // Add a branch to the merge point where the PHI node lives if it exists.
297 new BranchInst(AfterCallBB, RI);
299 // Delete the return instruction now
300 RI->getParent()->getInstList().erase(RI);
303 } else if (!Returns.empty()) {
304 // Otherwise, if there is exactly one return value, just replace anything
305 // using the return value of the call with the computed value.
306 if (!TheCall->use_empty())
307 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
309 // Splice the code from the return block into the block that it will return
310 // to, which contains the code that was after the call.
311 BasicBlock *ReturnBB = Returns[0]->getParent();
312 AfterCallBB->getInstList().splice(AfterCallBB->begin(),
313 ReturnBB->getInstList());
315 // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
316 ReturnBB->replaceAllUsesWith(AfterCallBB);
318 // Delete the return instruction now and empty ReturnBB now.
319 Returns[0]->getParent()->getInstList().erase(Returns[0]);
320 Caller->getBasicBlockList().erase(ReturnBB);
323 // Since we are now done with the Call/Invoke, we can delete it.
324 TheCall->getParent()->getInstList().erase(TheCall);
326 // We should always be able to fold the entry block of the function into the
327 // single predecessor of the block...
328 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
329 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
331 // Splice the code entry block into calling block, right before the
332 // unconditional branch.
333 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
334 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes
336 // Remove the unconditional branch.
337 OrigBB->getInstList().erase(Br);
339 // Now we can remove the CalleeEntry block, which is now empty.
340 Caller->getBasicBlockList().erase(CalleeEntry);