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