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//===- InlineFunction.cpp - Code to perform function inlining -------------===//
//
// This file implements inlining of a function into a call site, resolving
// parameters and the return value as appropriate.
//
// FIXME: This pass should transform alloca instructions in the called function
// into malloc/free pairs! Or perhaps it should refuse to inline them!
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/iTerminators.h"
#include "llvm/iPHINode.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/Transforms/Utils/Local.h"
// InlineFunction - This function inlines the called function into the basic
// block of the caller. This returns false if it is not possible to inline this
// call. The program is still in a well defined state if this occurs though.
//
// Note that this only does one level of inlining. For example, if the
// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
// exists in the instruction stream. Similiarly this will inline a recursive
// function by one level.
//
bool InlineFunction(CallInst *CI) {
assert(isa<CallInst>(CI) && "InlineFunction only works on CallInst nodes");
assert(CI->getParent() && "Instruction not embedded in basic block!");
assert(CI->getParent()->getParent() && "Instruction not in function!");
const Function *CalledFunc = CI->getCalledFunction();
if (CalledFunc == 0 || // Can't inline external function or indirect
CalledFunc->isExternal() || // call, or call to a vararg function!
CalledFunc->getFunctionType()->isVarArg()) return false;
BasicBlock *OrigBB = CI->getParent();
Function *Caller = OrigBB->getParent();
// Call splitBasicBlock - The original basic block now ends at the instruction
// immediately before the call. The original basic block now ends with an
// unconditional branch to NewBB, and NewBB starts with the call instruction.
//
BasicBlock *NewBB = OrigBB->splitBasicBlock(CI,
CalledFunc->getName()+".entry");
NewBB->setName(OrigBB->getName()+".split");
// Remove (unlink) the CallInst from the start of the new basic block.
NewBB->getInstList().remove(CI);
// If we have a return value generated by this call, convert it into a PHI
// node that gets values from each of the old RET instructions in the original
// function.
//
PHINode *PHI = 0;
if (!CI->use_empty()) {
// The PHI node should go at the front of the new basic block to merge all
// possible incoming values.
//
PHI = new PHINode(CalledFunc->getReturnType(), CI->getName(),
NewBB->begin());
// Anything that used the result of the function call should now use the PHI
// node as their operand.
//
CI->replaceAllUsesWith(PHI);
}
// Get an iterator to the last basic block in the function, which will have
// the new function inlined after it.
//
Function::iterator LastBlock = &Caller->back();
// Calculate the vector of arguments to pass into the function cloner...
std::map<const Value*, Value*> ValueMap;
assert((unsigned)std::distance(CalledFunc->abegin(), CalledFunc->aend()) ==
CI->getNumOperands()-1 && "No varargs calls can be inlined yet!");
unsigned i = 1;
for (Function::const_aiterator I = CalledFunc->abegin(), E=CalledFunc->aend();
I != E; ++I, ++i)
ValueMap[I] = CI->getOperand(i);
// Since we are now done with the CallInst, we can delete it.
delete CI;
// Make a vector to capture the return instructions in the cloned function...
std::vector<ReturnInst*> Returns;
// Populate the value map with all of the globals in the program.
Module &M = *Caller->getParent();
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
ValueMap[I] = I;
for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
ValueMap[I] = I;
// Do all of the hard part of cloning the callee into the caller...
CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i");
// Loop over all of the return instructions, turning them into unconditional
// branches to the merge point now...
for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
ReturnInst *RI = Returns[i];
BasicBlock *BB = RI->getParent();
// Add a branch to the merge point where the PHI node would live...
new BranchInst(NewBB, RI);
if (PHI) { // The PHI node should include this value!
assert(RI->getReturnValue() && "Ret should have value!");
assert(RI->getReturnValue()->getType() == PHI->getType() &&
"Ret value not consistent in function!");
PHI->addIncoming(RI->getReturnValue(), BB);
}
// Delete the return instruction now
BB->getInstList().erase(RI);
}
// Check to see if the PHI node only has one argument. This is a common
// case resulting from there only being a single return instruction in the
// function call. Because this is so common, eliminate the PHI node.
//
if (PHI && PHI->getNumIncomingValues() == 1) {
PHI->replaceAllUsesWith(PHI->getIncomingValue(0));
PHI->getParent()->getInstList().erase(PHI);
}
// Change the branch that used to go to NewBB to branch to the first basic
// block of the inlined function.
//
TerminatorInst *Br = OrigBB->getTerminator();
assert(Br && Br->getOpcode() == Instruction::Br &&
"splitBasicBlock broken!");
Br->setOperand(0, ++LastBlock);
// If there are any alloca instructions in the block that used to be the entry
// block for the callee, move them to the entry block of the caller. First
// calculate which instruction they should be inserted before. We insert the
// instructions at the end of the current alloca list.
//
BasicBlock::iterator InsertPoint = Caller->begin()->begin();
while (isa<AllocaInst>(InsertPoint)) ++InsertPoint;
for (BasicBlock::iterator I = LastBlock->begin(), E = LastBlock->end();
I != E; )
if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
++I; // Move to the next instruction
LastBlock->getInstList().remove(AI);
Caller->front().getInstList().insert(InsertPoint, AI);
} else {
++I;
}
// Now that the function is correct, make it a little bit nicer. In
// particular, move the basic blocks inserted from the end of the function
// into the space made by splitting the source basic block.
//
Caller->getBasicBlockList().splice(NewBB, Caller->getBasicBlockList(),
LastBlock, Caller->end());
// We should always be able to fold the entry block of the function into the
// single predecessor of the block...
assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
SimplifyCFG(CalleeEntry);
// Okay, continue the CFG cleanup. It's often the case that there is only a
// single return instruction in the callee function. If this is the case,
// then we have an unconditional branch from the return block to the 'NewBB'.
// Check for this case, and eliminate the branch is possible.
SimplifyCFG(NewBB);
return true;
}
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