| //===- 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) { |
| // 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); |
| } |
| |
| // 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. |
| new BranchInst(NewBB, IBB->end()); |
| 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 { |
| virtual bool runOnFunction(Function &F) { |
| return doFunctionInlining(F); |
| } |
| }; |
| RegisterOpt<FunctionInlining> X("inline", "Function Integration/Inlining"); |
| } |
| |
| Pass *createFunctionInliningPass() { return new FunctionInlining(); } |