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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@455 91177308-0d34-0410-b5e6-96231b3b80d8
265 lines
9.2 KiB
C++
265 lines
9.2 KiB
C++
//===- MethodInlining.cpp - Code to perform method inlining ---------------===//
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//
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// This file implements inlining of methods.
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//
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// Specifically, this:
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// * Exports functionality to inline any method call
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// * Inlines methods that consist of a single basic block
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// * Is able to inline ANY method call
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// . Has a smart heuristic for when to inline a method
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//
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// Notice that:
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// * This pass has a habit of introducing duplicated constant pool entries,
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// and also opens up a lot of opportunities for constant propogation. It is
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// a good idea to to run a constant propogation pass, then a DCE pass
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// sometime after running this pass.
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//
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// TODO: Currently this throws away all of the symbol names in the method being
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// inlined to try to avoid name clashes. Use a name if it's not taken
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Optimizations/MethodInlining.h"
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#include "llvm/Module.h"
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#include "llvm/Method.h"
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#include "llvm/iTerminators.h"
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#include "llvm/iOther.h"
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#include <algorithm>
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#include <map>
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#include "llvm/Assembly/Writer.h"
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using namespace opt;
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// RemapInstruction - Convert the instruction operands from referencing the
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// current values into those specified by ValueMap.
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//
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static inline void RemapInstruction(Instruction *I,
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map<const Value *, Value*> &ValueMap) {
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for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
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const Value *Op = I->getOperand(op);
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Value *V = ValueMap[Op];
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if (!V && (Op->isMethod() || Op->isConstant()))
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continue; // Methods and constants don't get relocated
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if (!V) {
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cerr << "Val = " << endl << Op << "Addr = " << (void*)Op << endl;
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cerr << "Inst = " << I;
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}
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assert(V && "Referenced value not in value map!");
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I->setOperand(op, V);
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}
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}
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// InlineMethod - This function forcibly inlines the called method into the
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// basic block of the caller. This returns false if it is not possible to
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// inline this call. The program is still in a well defined state if this
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// occurs though.
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//
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// Note that this only does one level of inlining. For example, if the
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// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
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// exists in the instruction stream. Similiarly this will inline a recursive
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// method by one level.
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//
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bool opt::InlineMethod(BasicBlock::iterator CIIt) {
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assert((*CIIt)->getOpcode() == Instruction::Call &&
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"InlineMethod only works on CallInst nodes!");
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assert((*CIIt)->getParent() && "Instruction not embedded in basic block!");
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assert((*CIIt)->getParent()->getParent() && "Instruction not in method!");
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CallInst *CI = (CallInst*)*CIIt;
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const Method *CalledMeth = CI->getCalledMethod();
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if (CalledMeth->isExternal()) return false; // Can't inline external method!
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Method *CurrentMeth = CI->getParent()->getParent();
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//cerr << "Inlining " << CalledMeth->getName() << " into "
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// << CurrentMeth->getName() << endl;
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BasicBlock *OrigBB = CI->getParent();
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// Call splitBasicBlock - The original basic block now ends at the instruction
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// immediately before the call. The original basic block now ends with an
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// unconditional branch to NewBB, and NewBB starts with the call instruction.
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//
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BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt);
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// Remove (unlink) the CallInst from the start of the new basic block.
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NewBB->getInstList().remove(CI);
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// If we have a return value generated by this call, convert it into a PHI
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// node that gets values from each of the old RET instructions in the original
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// method.
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//
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PHINode *PHI = 0;
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if (CalledMeth->getReturnType() != Type::VoidTy) {
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PHI = new PHINode(CalledMeth->getReturnType(), CI->getName());
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// The PHI node should go at the front of the new basic block to merge all
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// possible incoming values.
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//
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NewBB->getInstList().push_front(PHI);
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// Anything that used the result of the function call should now use the PHI
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// node as their operand.
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//
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CI->replaceAllUsesWith(PHI);
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}
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// Keep a mapping between the original method's values and the new duplicated
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// code's values. This includes all of: Method arguments, instruction values,
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// constant pool entries, and basic blocks.
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//
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map<const Value *, Value*> ValueMap;
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// Add the method arguments to the mapping: (start counting at 1 to skip the
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// method reference itself)
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//
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Method::ArgumentListType::const_iterator PTI =
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CalledMeth->getArgumentList().begin();
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for (unsigned a = 1, E = CI->getNumOperands(); a != E; ++a, ++PTI)
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ValueMap[*PTI] = CI->getOperand(a);
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ValueMap[NewBB] = NewBB; // Returns get converted to reference NewBB
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// Loop over all of the basic blocks in the method, inlining them as
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// appropriate. Keep track of the first basic block of the method...
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//
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for (Method::const_iterator BI = CalledMeth->begin();
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BI != CalledMeth->end(); ++BI) {
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const BasicBlock *BB = *BI;
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assert(BB->getTerminator() && "BasicBlock doesn't have terminator!?!?");
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// Create a new basic block to copy instructions into!
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BasicBlock *IBB = new BasicBlock("", NewBB->getParent());
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ValueMap[*BI] = IBB; // Add basic block mapping.
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// Make sure to capture the mapping that a return will use...
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// TODO: This assumes that the RET is returning a value computed in the same
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// basic block as the return was issued from!
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//
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const TerminatorInst *TI = BB->getTerminator();
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// Loop over all instructions copying them over...
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Instruction *NewInst;
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for (BasicBlock::const_iterator II = BB->begin();
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II != (BB->end()-1); ++II) {
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IBB->getInstList().push_back((NewInst = (*II)->clone()));
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ValueMap[*II] = NewInst; // Add instruction map to value.
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}
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// Copy over the terminator now...
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switch (TI->getOpcode()) {
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case Instruction::Ret: {
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const ReturnInst *RI = (const ReturnInst*)TI;
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if (PHI) { // The PHI node should include this value!
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assert(RI->getReturnValue() && "Ret should have value!");
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assert(RI->getReturnValue()->getType() == PHI->getType() &&
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"Ret value not consistent in method!");
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PHI->addIncoming((Value*)RI->getReturnValue(), (BasicBlock*)BB);
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}
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// Add a branch to the code that was after the original Call.
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IBB->getInstList().push_back(new BranchInst(NewBB));
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break;
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}
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case Instruction::Br:
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IBB->getInstList().push_back(TI->clone());
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break;
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default:
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cerr << "MethodInlining: Don't know how to handle terminator: " << TI;
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abort();
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}
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}
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// Loop over all of the instructions in the method, fixing up operand
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// references as we go. This uses ValueMap to do all the hard work.
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//
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for (Method::const_iterator BI = CalledMeth->begin();
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BI != CalledMeth->end(); ++BI) {
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const BasicBlock *BB = *BI;
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BasicBlock *NBB = (BasicBlock*)ValueMap[BB];
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// Loop over all instructions, fixing each one as we find it...
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//
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for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); II++)
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RemapInstruction(*II, ValueMap);
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}
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if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also...
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// Change the branch that used to go to NewBB to branch to the first basic
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// block of the inlined method.
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//
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TerminatorInst *Br = OrigBB->getTerminator();
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assert(Br && Br->getOpcode() == Instruction::Br &&
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"splitBasicBlock broken!");
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Br->setOperand(0, ValueMap[CalledMeth->front()]);
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// Since we are now done with the CallInst, we can finally delete it.
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delete CI;
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return true;
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}
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bool opt::InlineMethod(CallInst *CI) {
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assert(CI->getParent() && "CallInst not embeded in BasicBlock!");
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BasicBlock *PBB = CI->getParent();
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BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI);
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assert(CallIt != PBB->end() &&
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"CallInst has parent that doesn't contain CallInst?!?");
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return InlineMethod(CallIt);
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}
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static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) {
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assert(CI->getParent() && CI->getParent()->getParent() &&
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"Call not embedded into a method!");
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// Don't inline a recursive call.
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if (CI->getParent()->getParent() == M) return false;
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// Don't inline something too big. This is a really crappy heuristic
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if (M->size() > 3) return false;
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// Don't inline into something too big. This is a **really** crappy heuristic
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if (CI->getParent()->getParent()->size() > 10) return false;
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// Go ahead and try just about anything else.
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return true;
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}
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static inline bool DoMethodInlining(BasicBlock *BB) {
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for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
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if ((*I)->getOpcode() == Instruction::Call) {
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// Check to see if we should inline this method
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CallInst *CI = (CallInst*)*I;
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Method *M = CI->getCalledMethod();
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if (ShouldInlineMethod(CI, M))
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return InlineMethod(I);
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}
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}
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return false;
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}
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bool opt::DoMethodInlining(Method *M) {
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bool Changed = false;
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// Loop through now and inline instructions a basic block at a time...
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for (Method::iterator I = M->begin(); I != M->end(); )
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if (DoMethodInlining(*I)) {
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Changed = true;
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// Iterator is now invalidated by new basic blocks inserted
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I = M->begin();
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} else {
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++I;
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}
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return Changed;
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}
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