llvm-6502/lib/Transforms/IPO/InlineSimple.cpp

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//===- FunctionInlining.cpp - Code to perform function inlining -----------===//
//
// This file implements inlining of functions.
//
// Specifically, this:
// * Exports functionality to inline any function call
// * Inlines functions that consist of a single basic block
// * Is able to inline ANY function call
// . Has a smart heuristic for when to inline a function
//
// Notice that:
// * This pass opens up a lot of opportunities for constant propogation. It
// is a good idea to to run a constant propogation pass, then a DCE pass
// sometime after running this pass.
//
// FIXME: This pass should transform alloca instructions in the called function
// into malloc/free pairs!
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/FunctionInlining.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/iTerminators.h"
#include "llvm/iPHINode.h"
#include "llvm/iOther.h"
#include "llvm/Type.h"
#include "Support/StatisticReporter.h"
#include <algorithm>
#include <iostream>
static Statistic<> NumInlined("inline\t\t- Number of functions inlined");
using std::cerr;
// RemapInstruction - Convert the instruction operands from referencing the
// current values into those specified by ValueMap.
//
static inline void RemapInstruction(Instruction *I,
std::map<const Value *, Value*> &ValueMap) {
for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
const Value *Op = I->getOperand(op);
Value *V = ValueMap[Op];
if (!V && (isa<GlobalValue>(Op) || isa<Constant>(Op)))
continue; // Globals and constants don't get relocated
if (!V) {
cerr << "Val = \n" << Op << "Addr = " << (void*)Op;
cerr << "\nInst = " << I;
}
assert(V && "Referenced value not in value map!");
I->setOperand(op, V);
}
}
// InlineFunction - This function forcibly 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 call!
CalledFunc->isExternal()) return false;
//cerr << "Inlining " << CalledFunc->getName() << " into "
// << CurrentMeth->getName() << "\n";
BasicBlock *OrigBB = CI->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);
NewBB->setName("InlinedFunctionReturnNode");
// 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 (CalledFunc->getReturnType() != Type::VoidTy) {
PHI = new PHINode(CalledFunc->getReturnType(), CI->getName());
// The PHI node should go at the front of the new basic block to merge all
// possible incoming values.
//
NewBB->getInstList().push_front(PHI);
// Anything that used the result of the function call should now use the PHI
// node as their operand.
//
CI->replaceAllUsesWith(PHI);
}
// Keep a mapping between the original function's values and the new
// duplicated code's values. This includes all of: Function arguments,
// instruction values, constant pool entries, and basic blocks.
//
std::map<const Value *, Value*> ValueMap;
// Add the function arguments to the mapping: (start counting at 1 to skip the
// function reference itself)
//
Function::const_aiterator PTI = CalledFunc->abegin();
for (unsigned a = 1, E = CI->getNumOperands(); a != E; ++a, ++PTI)
ValueMap[PTI] = CI->getOperand(a);
ValueMap[NewBB] = NewBB; // Returns get converted to reference NewBB
// Loop over all of the basic blocks in the function, inlining them as
// appropriate. Keep track of the first basic block of the function...
//
for (Function::const_iterator BB = CalledFunc->begin();
BB != CalledFunc->end(); ++BB) {
assert(BB->getTerminator() && "BasicBlock doesn't have terminator!?!?");
// Create a new basic block to copy instructions into!
BasicBlock *IBB = new BasicBlock("", NewBB->getParent());
if (BB->hasName()) IBB->setName(BB->getName()+".i"); // .i = inlined once
ValueMap[BB] = IBB; // Add basic block mapping.
// Make sure to capture the mapping that a return will use...
// TODO: This assumes that the RET is returning a value computed in the same
// basic block as the return was issued from!
//
const TerminatorInst *TI = BB->getTerminator();
// Loop over all instructions copying them over...
Instruction *NewInst;
for (BasicBlock::const_iterator II = BB->begin();
II != --BB->end(); ++II) {
IBB->getInstList().push_back((NewInst = II->clone()));
ValueMap[II] = NewInst; // Add instruction map to value.
if (II->hasName())
NewInst->setName(II->getName()+".i"); // .i = inlined once
}
// Copy over the terminator now...
switch (TI->getOpcode()) {
case Instruction::Ret: {
const ReturnInst *RI = cast<ReturnInst>(TI);
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((Value*)RI->getReturnValue(),
(BasicBlock*)cast<BasicBlock>(&*BB));
}
// Add a branch to the code that was after the original Call.
IBB->getInstList().push_back(new BranchInst(NewBB));
break;
}
case Instruction::Br:
IBB->getInstList().push_back(TI->clone());
break;
default:
cerr << "FunctionInlining: Don't know how to handle terminator: " << TI;
abort();
}
}
// Loop over all of the instructions in the function, fixing up operand
// references as we go. This uses ValueMap to do all the hard work.
//
for (Function::const_iterator BB = CalledFunc->begin();
BB != CalledFunc->end(); ++BB) {
BasicBlock *NBB = (BasicBlock*)ValueMap[BB];
// Loop over all instructions, fixing each one as we find it...
//
for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); ++II)
RemapInstruction(II, ValueMap);
}
if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also...
// 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, ValueMap[&CalledFunc->front()]);
// Since we are now done with the CallInst, we can finally delete it.
delete CI;
return true;
}
static inline bool ShouldInlineFunction(const CallInst *CI, const Function *F) {
assert(CI->getParent() && CI->getParent()->getParent() &&
"Call not embedded into a function!");
// Don't inline a recursive call.
if (CI->getParent()->getParent() == F) return false;
// Don't inline something too big. This is a really crappy heuristic
if (F->size() > 3) return false;
// Don't inline into something too big. This is a **really** crappy heuristic
if (CI->getParent()->getParent()->size() > 10) return false;
// Go ahead and try just about anything else.
return true;
}
static inline bool DoFunctionInlining(BasicBlock *BB) {
for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
if (CallInst *CI = dyn_cast<CallInst>(&*I)) {
// Check to see if we should inline this function
Function *F = CI->getCalledFunction();
if (F && ShouldInlineFunction(CI, F)) {
return InlineFunction(CI);
}
}
}
return false;
}
// doFunctionInlining - Use a heuristic based approach to inline functions that
// seem to look good.
//
static bool doFunctionInlining(Function &F) {
bool Changed = false;
// Loop through now and inline instructions a basic block at a time...
for (Function::iterator I = F.begin(); I != F.end(); )
if (DoFunctionInlining(I)) {
++NumInlined;
Changed = true;
} else {
++I;
}
return Changed;
}
namespace {
struct FunctionInlining : public FunctionPass {
const char *getPassName() const { return "Function Inlining"; }
virtual bool runOnFunction(Function &F) {
return doFunctionInlining(F);
}
};
}
Pass *createFunctionInliningPass() { return new FunctionInlining(); }