llvm-6502/lib/Transforms/IPO/InlineSimple.cpp
2001-10-18 01:32:34 +00:00

264 lines
9.2 KiB
C++

//===- MethodInlining.cpp - Code to perform method inlining ---------------===//
//
// This file implements inlining of methods.
//
// Specifically, this:
// * Exports functionality to inline any method call
// * Inlines methods that consist of a single basic block
// * Is able to inline ANY method call
// . Has a smart heuristic for when to inline a method
//
// Notice that:
// * This pass has a habit of introducing duplicated constant pool entries,
// and also 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.
//
// TODO: Currently this throws away all of the symbol names in the method being
// inlined to try to avoid name clashes. Use a name if it's not taken
//
//===----------------------------------------------------------------------===//
#include "llvm/Optimizations/MethodInlining.h"
#include "llvm/Module.h"
#include "llvm/Method.h"
#include "llvm/iTerminators.h"
#include "llvm/iOther.h"
#include <algorithm>
#include <map>
#include "llvm/Assembly/Writer.h"
using namespace opt;
// RemapInstruction - Convert the instruction operands from referencing the
// current values into those specified by ValueMap.
//
static inline void RemapInstruction(Instruction *I,
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<Method>(Op) || isa<ConstPoolVal>(Op)))
continue; // Methods and constants don't get relocated
if (!V) {
cerr << "Val = " << endl << Op << "Addr = " << (void*)Op << endl;
cerr << "Inst = " << I;
}
assert(V && "Referenced value not in value map!");
I->setOperand(op, V);
}
}
// InlineMethod - This function forcibly inlines the called method 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
// method by one level.
//
bool opt::InlineMethod(BasicBlock::iterator CIIt) {
assert(isa<CallInst>(*CIIt) && "InlineMethod only works on CallInst nodes!");
assert((*CIIt)->getParent() && "Instruction not embedded in basic block!");
assert((*CIIt)->getParent()->getParent() && "Instruction not in method!");
CallInst *CI = cast<CallInst>(*CIIt);
const Method *CalledMeth = CI->getCalledMethod();
if (CalledMeth == 0 || // Can't inline external method or indirect call!
CalledMeth->isExternal()) return false;
Method *CurrentMeth = CI->getParent()->getParent();
//cerr << "Inlining " << CalledMeth->getName() << " into "
// << CurrentMeth->getName() << endl;
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(CIIt);
// 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
// method.
//
PHINode *PHI = 0;
if (CalledMeth->getReturnType() != Type::VoidTy) {
PHI = new PHINode(CalledMeth->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 method's values and the new duplicated
// code's values. This includes all of: Method arguments, instruction values,
// constant pool entries, and basic blocks.
//
map<const Value *, Value*> ValueMap;
// Add the method arguments to the mapping: (start counting at 1 to skip the
// method reference itself)
//
Method::ArgumentListType::const_iterator PTI =
CalledMeth->getArgumentList().begin();
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 method, inlining them as
// appropriate. Keep track of the first basic block of the method...
//
for (Method::const_iterator BI = CalledMeth->begin();
BI != CalledMeth->end(); ++BI) {
const BasicBlock *BB = *BI;
assert(BB->getTerminator() && "BasicBlock doesn't have terminator!?!?");
// Create a new basic block to copy instructions into!
BasicBlock *IBB = new BasicBlock("", NewBB->getParent());
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()-1); ++II) {
IBB->getInstList().push_back((NewInst = (*II)->clone()));
ValueMap[*II] = NewInst; // Add instruction map to value.
}
// Copy over the terminator now...
switch (TI->getOpcode()) {
case Instruction::Ret: {
const ReturnInst *RI = cast<const 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 method!");
PHI->addIncoming((Value*)RI->getReturnValue(), 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 << "MethodInlining: Don't know how to handle terminator: " << TI;
abort();
}
}
// Loop over all of the instructions in the method, fixing up operand
// references as we go. This uses ValueMap to do all the hard work.
//
for (Method::const_iterator BI = CalledMeth->begin();
BI != CalledMeth->end(); ++BI) {
const BasicBlock *BB = *BI;
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 method.
//
TerminatorInst *Br = OrigBB->getTerminator();
assert(Br && Br->getOpcode() == Instruction::Br &&
"splitBasicBlock broken!");
Br->setOperand(0, ValueMap[CalledMeth->front()]);
// Since we are now done with the CallInst, we can finally delete it.
delete CI;
return true;
}
bool opt::InlineMethod(CallInst *CI) {
assert(CI->getParent() && "CallInst not embeded in BasicBlock!");
BasicBlock *PBB = CI->getParent();
BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI);
assert(CallIt != PBB->end() &&
"CallInst has parent that doesn't contain CallInst?!?");
return InlineMethod(CallIt);
}
static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) {
assert(CI->getParent() && CI->getParent()->getParent() &&
"Call not embedded into a method!");
// Don't inline a recursive call.
if (CI->getParent()->getParent() == M) return false;
// Don't inline something too big. This is a really crappy heuristic
if (M->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 DoMethodInlining(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 method
Method *M = CI->getCalledMethod();
if (M && ShouldInlineMethod(CI, M))
return InlineMethod(I);
}
}
return false;
}
bool opt::MethodInlining::doMethodInlining(Method *M) {
bool Changed = false;
// Loop through now and inline instructions a basic block at a time...
for (Method::iterator I = M->begin(); I != M->end(); )
if (DoMethodInlining(*I)) {
Changed = true;
// Iterator is now invalidated by new basic blocks inserted
I = M->begin();
} else {
++I;
}
return Changed;
}