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/DerivedTypes.h"
13 #include "llvm/Module.h"
14 #include "llvm/iTerminators.h"
15 #include "llvm/iPHINode.h"
16 #include "llvm/iMemory.h"
17 #include "llvm/iOther.h"
18 #include "llvm/Transforms/Utils/Local.h"
20 // InlineFunction - This function inlines the called function into the basic
21 // block of the caller. This returns false if it is not possible to inline this
22 // call. The program is still in a well defined state if this occurs though.
24 // Note that this only does one level of inlining. For example, if the
25 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
26 // exists in the instruction stream. Similiarly this will inline a recursive
27 // function by one level.
29 bool InlineFunction(CallInst *CI) {
30 assert(isa<CallInst>(CI) && "InlineFunction only works on CallInst nodes");
31 assert(CI->getParent() && "Instruction not embedded in basic block!");
32 assert(CI->getParent()->getParent() && "Instruction not in function!");
34 const Function *CalledFunc = CI->getCalledFunction();
35 if (CalledFunc == 0 || // Can't inline external function or indirect
36 CalledFunc->isExternal() || // call, or call to a vararg function!
37 CalledFunc->getFunctionType()->isVarArg()) return false;
39 BasicBlock *OrigBB = CI->getParent();
40 Function *Caller = OrigBB->getParent();
42 // Call splitBasicBlock - The original basic block now ends at the instruction
43 // immediately before the call. The original basic block now ends with an
44 // unconditional branch to NewBB, and NewBB starts with the call instruction.
46 BasicBlock *NewBB = OrigBB->splitBasicBlock(CI,
47 CalledFunc->getName()+".entry");
48 NewBB->setName(OrigBB->getName()+".split");
50 // Remove (unlink) the CallInst from the start of the new basic block.
51 NewBB->getInstList().remove(CI);
53 // If we have a return value generated by this call, convert it into a PHI
54 // node that gets values from each of the old RET instructions in the original
58 if (!CI->use_empty()) {
59 // The PHI node should go at the front of the new basic block to merge all
60 // possible incoming values.
62 PHI = new PHINode(CalledFunc->getReturnType(), CI->getName(),
65 // Anything that used the result of the function call should now use the PHI
66 // node as their operand.
68 CI->replaceAllUsesWith(PHI);
71 // Get an iterator to the last basic block in the function, which will have
72 // the new function inlined after it.
74 Function::iterator LastBlock = &Caller->back();
76 // Calculate the vector of arguments to pass into the function cloner...
77 std::map<const Value*, Value*> ValueMap;
78 assert((unsigned)std::distance(CalledFunc->abegin(), CalledFunc->aend()) ==
79 CI->getNumOperands()-1 && "No varargs calls can be inlined yet!");
82 for (Function::const_aiterator I = CalledFunc->abegin(), E=CalledFunc->aend();
84 ValueMap[I] = CI->getOperand(i);
86 // Since we are now done with the CallInst, we can delete it.
89 // Make a vector to capture the return instructions in the cloned function...
90 std::vector<ReturnInst*> Returns;
92 // Populate the value map with all of the globals in the program.
93 Module &M = *Caller->getParent();
94 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
96 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
99 // Do all of the hard part of cloning the callee into the caller...
100 CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i");
102 // Loop over all of the return instructions, turning them into unconditional
103 // branches to the merge point now...
104 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
105 ReturnInst *RI = Returns[i];
106 BasicBlock *BB = RI->getParent();
108 // Add a branch to the merge point where the PHI node would live...
109 new BranchInst(NewBB, RI);
111 if (PHI) { // The PHI node should include this value!
112 assert(RI->getReturnValue() && "Ret should have value!");
113 assert(RI->getReturnValue()->getType() == PHI->getType() &&
114 "Ret value not consistent in function!");
115 PHI->addIncoming(RI->getReturnValue(), BB);
118 // Delete the return instruction now
119 BB->getInstList().erase(RI);
122 // Check to see if the PHI node only has one argument. This is a common
123 // case resulting from there only being a single return instruction in the
124 // function call. Because this is so common, eliminate the PHI node.
126 if (PHI && PHI->getNumIncomingValues() == 1) {
127 PHI->replaceAllUsesWith(PHI->getIncomingValue(0));
128 PHI->getParent()->getInstList().erase(PHI);
131 // Change the branch that used to go to NewBB to branch to the first basic
132 // block of the inlined function.
134 TerminatorInst *Br = OrigBB->getTerminator();
135 assert(Br && Br->getOpcode() == Instruction::Br &&
136 "splitBasicBlock broken!");
137 Br->setOperand(0, ++LastBlock);
139 // If there are any alloca instructions in the block that used to be the entry
140 // block for the callee, move them to the entry block of the caller. First
141 // calculate which instruction they should be inserted before. We insert the
142 // instructions at the end of the current alloca list.
144 BasicBlock::iterator InsertPoint = Caller->begin()->begin();
145 while (isa<AllocaInst>(InsertPoint)) ++InsertPoint;
147 for (BasicBlock::iterator I = LastBlock->begin(), E = LastBlock->end();
149 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
150 ++I; // Move to the next instruction
151 LastBlock->getInstList().remove(AI);
152 Caller->front().getInstList().insert(InsertPoint, AI);
158 // Now that the function is correct, make it a little bit nicer. In
159 // particular, move the basic blocks inserted from the end of the function
160 // into the space made by splitting the source basic block.
162 Caller->getBasicBlockList().splice(NewBB, Caller->getBasicBlockList(),
163 LastBlock, Caller->end());
165 // We should always be able to fold the entry block of the function into the
166 // single predecessor of the block...
167 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
168 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
169 SimplifyCFG(CalleeEntry);
171 // Okay, continue the CFG cleanup. It's often the case that there is only a
172 // single return instruction in the callee function. If this is the case,
173 // then we have an unconditional branch from the return block to the 'NewBB'.
174 // Check for this case, and eliminate the branch is possible.