mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-30 21:29:28 +00:00
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92726 91177308-0d34-0410-b5e6-96231b3b80d8
666 lines
21 KiB
C++
666 lines
21 KiB
C++
//===- MergeFunctions.cpp - Merge identical functions ---------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass looks for equivalent functions that are mergable and folds them.
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//
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// A hash is computed from the function, based on its type and number of
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// basic blocks.
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//
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// Once all hashes are computed, we perform an expensive equality comparison
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// on each function pair. This takes n^2/2 comparisons per bucket, so it's
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// important that the hash function be high quality. The equality comparison
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// iterates through each instruction in each basic block.
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//
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// When a match is found, the functions are folded. We can only fold two
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// functions when we know that the definition of one of them is not
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// overridable.
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//
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//===----------------------------------------------------------------------===//
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//
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// Future work:
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//
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// * fold vector<T*>::push_back and vector<S*>::push_back.
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//
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// These two functions have different types, but in a way that doesn't matter
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// to us. As long as we never see an S or T itself, using S* and S** is the
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// same as using a T* and T**.
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//
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// * virtual functions.
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//
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// Many functions have their address taken by the virtual function table for
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// the object they belong to. However, as long as it's only used for a lookup
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// and call, this is irrelevant, and we'd like to fold such implementations.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "mergefunc"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/FoldingSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Constants.h"
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#include "llvm/InlineAsm.h"
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#include "llvm/Instructions.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include <map>
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#include <vector>
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using namespace llvm;
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STATISTIC(NumFunctionsMerged, "Number of functions merged");
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namespace {
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struct MergeFunctions : public ModulePass {
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static char ID; // Pass identification, replacement for typeid
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MergeFunctions() : ModulePass(&ID) {}
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bool runOnModule(Module &M);
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};
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}
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char MergeFunctions::ID = 0;
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static RegisterPass<MergeFunctions>
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X("mergefunc", "Merge Functions");
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ModulePass *llvm::createMergeFunctionsPass() {
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return new MergeFunctions();
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}
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// ===----------------------------------------------------------------------===
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// Comparison of functions
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// ===----------------------------------------------------------------------===
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static unsigned long hash(const Function *F) {
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const FunctionType *FTy = F->getFunctionType();
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FoldingSetNodeID ID;
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ID.AddInteger(F->size());
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ID.AddInteger(F->getCallingConv());
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ID.AddBoolean(F->hasGC());
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ID.AddBoolean(FTy->isVarArg());
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ID.AddInteger(FTy->getReturnType()->getTypeID());
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for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
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ID.AddInteger(FTy->getParamType(i)->getTypeID());
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return ID.ComputeHash();
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}
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/// IgnoreBitcasts - given a bitcast, returns the first non-bitcast found by
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/// walking the chain of cast operands. Otherwise, returns the argument.
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static Value* IgnoreBitcasts(Value *V) {
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while (BitCastInst *BC = dyn_cast<BitCastInst>(V))
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V = BC->getOperand(0);
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return V;
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}
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/// isEquivalentType - any two pointers are equivalent. Otherwise, standard
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/// type equivalence rules apply.
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static bool isEquivalentType(const Type *Ty1, const Type *Ty2) {
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if (Ty1 == Ty2)
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return true;
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if (Ty1->getTypeID() != Ty2->getTypeID())
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return false;
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switch(Ty1->getTypeID()) {
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case Type::VoidTyID:
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case Type::FloatTyID:
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case Type::DoubleTyID:
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case Type::X86_FP80TyID:
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case Type::FP128TyID:
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case Type::PPC_FP128TyID:
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case Type::LabelTyID:
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case Type::MetadataTyID:
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return true;
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case Type::IntegerTyID:
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case Type::OpaqueTyID:
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// Ty1 == Ty2 would have returned true earlier.
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return false;
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default:
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llvm_unreachable("Unknown type!");
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return false;
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case Type::PointerTyID: {
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const PointerType *PTy1 = cast<PointerType>(Ty1);
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const PointerType *PTy2 = cast<PointerType>(Ty2);
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return PTy1->getAddressSpace() == PTy2->getAddressSpace();
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}
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case Type::StructTyID: {
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const StructType *STy1 = cast<StructType>(Ty1);
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const StructType *STy2 = cast<StructType>(Ty2);
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if (STy1->getNumElements() != STy2->getNumElements())
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return false;
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if (STy1->isPacked() != STy2->isPacked())
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return false;
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for (unsigned i = 0, e = STy1->getNumElements(); i != e; ++i) {
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if (!isEquivalentType(STy1->getElementType(i), STy2->getElementType(i)))
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return false;
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}
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return true;
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}
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case Type::FunctionTyID: {
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const FunctionType *FTy1 = cast<FunctionType>(Ty1);
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const FunctionType *FTy2 = cast<FunctionType>(Ty2);
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if (FTy1->getNumParams() != FTy2->getNumParams() ||
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FTy1->isVarArg() != FTy2->isVarArg())
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return false;
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if (!isEquivalentType(FTy1->getReturnType(), FTy2->getReturnType()))
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return false;
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for (unsigned i = 0, e = FTy1->getNumParams(); i != e; ++i) {
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if (!isEquivalentType(FTy1->getParamType(i), FTy2->getParamType(i)))
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return false;
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}
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return true;
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}
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case Type::ArrayTyID:
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case Type::VectorTyID: {
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const SequentialType *STy1 = cast<SequentialType>(Ty1);
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const SequentialType *STy2 = cast<SequentialType>(Ty2);
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return isEquivalentType(STy1->getElementType(), STy2->getElementType());
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}
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}
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}
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/// isEquivalentOperation - determine whether the two operations are the same
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/// except that pointer-to-A and pointer-to-B are equivalent. This should be
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/// kept in sync with Instruction::isSameOperationAs.
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static bool
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isEquivalentOperation(const Instruction *I1, const Instruction *I2) {
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if (I1->getOpcode() != I2->getOpcode() ||
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I1->getNumOperands() != I2->getNumOperands() ||
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!isEquivalentType(I1->getType(), I2->getType()) ||
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!I1->hasSameSubclassOptionalData(I2))
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return false;
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// We have two instructions of identical opcode and #operands. Check to see
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// if all operands are the same type
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for (unsigned i = 0, e = I1->getNumOperands(); i != e; ++i)
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if (!isEquivalentType(I1->getOperand(i)->getType(),
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I2->getOperand(i)->getType()))
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return false;
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// Check special state that is a part of some instructions.
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if (const LoadInst *LI = dyn_cast<LoadInst>(I1))
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return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() &&
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LI->getAlignment() == cast<LoadInst>(I2)->getAlignment();
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if (const StoreInst *SI = dyn_cast<StoreInst>(I1))
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return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() &&
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SI->getAlignment() == cast<StoreInst>(I2)->getAlignment();
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if (const CmpInst *CI = dyn_cast<CmpInst>(I1))
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return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate();
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if (const CallInst *CI = dyn_cast<CallInst>(I1))
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return CI->isTailCall() == cast<CallInst>(I2)->isTailCall() &&
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CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
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CI->getAttributes().getRawPointer() ==
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cast<CallInst>(I2)->getAttributes().getRawPointer();
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if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1))
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return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() &&
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CI->getAttributes().getRawPointer() ==
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cast<InvokeInst>(I2)->getAttributes().getRawPointer();
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if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1)) {
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if (IVI->getNumIndices() != cast<InsertValueInst>(I2)->getNumIndices())
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return false;
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for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
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if (IVI->idx_begin()[i] != cast<InsertValueInst>(I2)->idx_begin()[i])
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return false;
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return true;
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}
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if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1)) {
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if (EVI->getNumIndices() != cast<ExtractValueInst>(I2)->getNumIndices())
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return false;
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for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
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if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I2)->idx_begin()[i])
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return false;
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return true;
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}
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return true;
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}
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static bool compare(const Value *V, const Value *U) {
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assert(!isa<BasicBlock>(V) && !isa<BasicBlock>(U) &&
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"Must not compare basic blocks.");
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assert(isEquivalentType(V->getType(), U->getType()) &&
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"Two of the same operation have operands of different type.");
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// TODO: If the constant is an expression of F, we should accept that it's
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// equal to the same expression in terms of G.
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if (isa<Constant>(V))
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return V == U;
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// The caller has ensured that ValueMap[V] != U. Since Arguments are
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// pre-loaded into the ValueMap, and Instructions are added as we go, we know
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// that this can only be a mis-match.
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if (isa<Instruction>(V) || isa<Argument>(V))
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return false;
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if (isa<InlineAsm>(V) && isa<InlineAsm>(U)) {
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const InlineAsm *IAF = cast<InlineAsm>(V);
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const InlineAsm *IAG = cast<InlineAsm>(U);
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return IAF->getAsmString() == IAG->getAsmString() &&
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IAF->getConstraintString() == IAG->getConstraintString();
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}
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return false;
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}
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static bool equals(const BasicBlock *BB1, const BasicBlock *BB2,
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DenseMap<const Value *, const Value *> &ValueMap,
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DenseMap<const Value *, const Value *> &SpeculationMap) {
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// Speculatively add it anyways. If it's false, we'll notice a difference
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// later, and this won't matter.
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ValueMap[BB1] = BB2;
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BasicBlock::const_iterator FI = BB1->begin(), FE = BB1->end();
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BasicBlock::const_iterator GI = BB2->begin(), GE = BB2->end();
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do {
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if (isa<BitCastInst>(FI)) {
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++FI;
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continue;
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}
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if (isa<BitCastInst>(GI)) {
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++GI;
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continue;
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}
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if (!isEquivalentOperation(FI, GI))
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return false;
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if (isa<GetElementPtrInst>(FI)) {
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const GetElementPtrInst *GEPF = cast<GetElementPtrInst>(FI);
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const GetElementPtrInst *GEPG = cast<GetElementPtrInst>(GI);
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if (GEPF->hasAllZeroIndices() && GEPG->hasAllZeroIndices()) {
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// It's effectively a bitcast.
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++FI, ++GI;
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continue;
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}
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// TODO: we only really care about the elements before the index
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if (FI->getOperand(0)->getType() != GI->getOperand(0)->getType())
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return false;
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}
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if (ValueMap[FI] == GI) {
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++FI, ++GI;
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continue;
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}
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if (ValueMap[FI] != NULL)
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return false;
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for (unsigned i = 0, e = FI->getNumOperands(); i != e; ++i) {
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Value *OpF = IgnoreBitcasts(FI->getOperand(i));
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Value *OpG = IgnoreBitcasts(GI->getOperand(i));
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if (ValueMap[OpF] == OpG)
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continue;
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if (ValueMap[OpF] != NULL)
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return false;
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if (OpF->getValueID() != OpG->getValueID() ||
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!isEquivalentType(OpF->getType(), OpG->getType()))
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return false;
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if (isa<PHINode>(FI)) {
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if (SpeculationMap[OpF] == NULL)
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SpeculationMap[OpF] = OpG;
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else if (SpeculationMap[OpF] != OpG)
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return false;
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continue;
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} else if (isa<BasicBlock>(OpF)) {
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assert(isa<TerminatorInst>(FI) &&
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"BasicBlock referenced by non-Terminator non-PHI");
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// This call changes the ValueMap, hence we can't use
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// Value *& = ValueMap[...]
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if (!equals(cast<BasicBlock>(OpF), cast<BasicBlock>(OpG), ValueMap,
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SpeculationMap))
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return false;
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} else {
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if (!compare(OpF, OpG))
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return false;
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}
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ValueMap[OpF] = OpG;
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}
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ValueMap[FI] = GI;
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++FI, ++GI;
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} while (FI != FE && GI != GE);
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return FI == FE && GI == GE;
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}
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static bool equals(const Function *F, const Function *G) {
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// We need to recheck everything, but check the things that weren't included
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// in the hash first.
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if (F->getAttributes() != G->getAttributes())
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return false;
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if (F->hasGC() != G->hasGC())
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return false;
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if (F->hasGC() && F->getGC() != G->getGC())
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return false;
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if (F->hasSection() != G->hasSection())
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return false;
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if (F->hasSection() && F->getSection() != G->getSection())
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return false;
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if (F->isVarArg() != G->isVarArg())
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return false;
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// TODO: if it's internal and only used in direct calls, we could handle this
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// case too.
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if (F->getCallingConv() != G->getCallingConv())
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return false;
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if (!isEquivalentType(F->getFunctionType(), G->getFunctionType()))
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return false;
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DenseMap<const Value *, const Value *> ValueMap;
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DenseMap<const Value *, const Value *> SpeculationMap;
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ValueMap[F] = G;
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assert(F->arg_size() == G->arg_size() &&
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"Identical functions have a different number of args.");
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for (Function::const_arg_iterator fi = F->arg_begin(), gi = G->arg_begin(),
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fe = F->arg_end(); fi != fe; ++fi, ++gi)
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ValueMap[fi] = gi;
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if (!equals(&F->getEntryBlock(), &G->getEntryBlock(), ValueMap,
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SpeculationMap))
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return false;
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for (DenseMap<const Value *, const Value *>::iterator
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I = SpeculationMap.begin(), E = SpeculationMap.end(); I != E; ++I) {
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if (ValueMap[I->first] != I->second)
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return false;
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}
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return true;
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}
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// ===----------------------------------------------------------------------===
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// Folding of functions
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// ===----------------------------------------------------------------------===
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// Cases:
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// * F is external strong, G is external strong:
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// turn G into a thunk to F (1)
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// * F is external strong, G is external weak:
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// turn G into a thunk to F (1)
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// * F is external weak, G is external weak:
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// unfoldable
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// * F is external strong, G is internal:
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// address of G taken:
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// turn G into a thunk to F (1)
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// address of G not taken:
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// make G an alias to F (2)
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// * F is internal, G is external weak
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// address of F is taken:
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// turn G into a thunk to F (1)
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// address of F is not taken:
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// make G an alias of F (2)
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// * F is internal, G is internal:
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// address of F and G are taken:
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// turn G into a thunk to F (1)
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// address of G is not taken:
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// make G an alias to F (2)
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//
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// alias requires linkage == (external,local,weak) fallback to creating a thunk
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// external means 'externally visible' linkage != (internal,private)
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// internal means linkage == (internal,private)
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// weak means linkage mayBeOverridable
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// being external implies that the address is taken
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//
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// 1. turn G into a thunk to F
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// 2. make G an alias to F
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enum LinkageCategory {
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ExternalStrong,
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ExternalWeak,
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Internal
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};
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static LinkageCategory categorize(const Function *F) {
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switch (F->getLinkage()) {
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case GlobalValue::InternalLinkage:
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case GlobalValue::PrivateLinkage:
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case GlobalValue::LinkerPrivateLinkage:
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return Internal;
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case GlobalValue::WeakAnyLinkage:
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case GlobalValue::WeakODRLinkage:
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case GlobalValue::ExternalWeakLinkage:
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return ExternalWeak;
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case GlobalValue::ExternalLinkage:
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case GlobalValue::AvailableExternallyLinkage:
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case GlobalValue::LinkOnceAnyLinkage:
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case GlobalValue::LinkOnceODRLinkage:
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case GlobalValue::AppendingLinkage:
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case GlobalValue::DLLImportLinkage:
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case GlobalValue::DLLExportLinkage:
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case GlobalValue::GhostLinkage:
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case GlobalValue::CommonLinkage:
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return ExternalStrong;
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}
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llvm_unreachable("Unknown LinkageType.");
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return ExternalWeak;
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}
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static void ThunkGToF(Function *F, Function *G) {
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Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
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G->getParent());
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BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
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std::vector<Value *> Args;
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unsigned i = 0;
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const FunctionType *FFTy = F->getFunctionType();
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for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end();
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AI != AE; ++AI) {
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if (FFTy->getParamType(i) == AI->getType())
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Args.push_back(AI);
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else {
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Value *BCI = new BitCastInst(AI, FFTy->getParamType(i), "", BB);
|
|
Args.push_back(BCI);
|
|
}
|
|
++i;
|
|
}
|
|
|
|
CallInst *CI = CallInst::Create(F, Args.begin(), Args.end(), "", BB);
|
|
CI->setTailCall();
|
|
CI->setCallingConv(F->getCallingConv());
|
|
if (NewG->getReturnType()->isVoidTy()) {
|
|
ReturnInst::Create(F->getContext(), BB);
|
|
} else if (CI->getType() != NewG->getReturnType()) {
|
|
Value *BCI = new BitCastInst(CI, NewG->getReturnType(), "", BB);
|
|
ReturnInst::Create(F->getContext(), BCI, BB);
|
|
} else {
|
|
ReturnInst::Create(F->getContext(), CI, BB);
|
|
}
|
|
|
|
NewG->copyAttributesFrom(G);
|
|
NewG->takeName(G);
|
|
G->replaceAllUsesWith(NewG);
|
|
G->eraseFromParent();
|
|
|
|
// TODO: look at direct callers to G and make them all direct callers to F.
|
|
}
|
|
|
|
static void AliasGToF(Function *F, Function *G) {
|
|
if (!G->hasExternalLinkage() && !G->hasLocalLinkage() && !G->hasWeakLinkage())
|
|
return ThunkGToF(F, G);
|
|
|
|
GlobalAlias *GA = new GlobalAlias(
|
|
G->getType(), G->getLinkage(), "",
|
|
ConstantExpr::getBitCast(F, G->getType()), G->getParent());
|
|
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
|
|
GA->takeName(G);
|
|
GA->setVisibility(G->getVisibility());
|
|
G->replaceAllUsesWith(GA);
|
|
G->eraseFromParent();
|
|
}
|
|
|
|
static bool fold(std::vector<Function *> &FnVec, unsigned i, unsigned j) {
|
|
Function *F = FnVec[i];
|
|
Function *G = FnVec[j];
|
|
|
|
LinkageCategory catF = categorize(F);
|
|
LinkageCategory catG = categorize(G);
|
|
|
|
if (catF == ExternalWeak || (catF == Internal && catG == ExternalStrong)) {
|
|
std::swap(FnVec[i], FnVec[j]);
|
|
std::swap(F, G);
|
|
std::swap(catF, catG);
|
|
}
|
|
|
|
switch (catF) {
|
|
case ExternalStrong:
|
|
switch (catG) {
|
|
case ExternalStrong:
|
|
case ExternalWeak:
|
|
ThunkGToF(F, G);
|
|
break;
|
|
case Internal:
|
|
if (G->hasAddressTaken())
|
|
ThunkGToF(F, G);
|
|
else
|
|
AliasGToF(F, G);
|
|
break;
|
|
}
|
|
break;
|
|
|
|
case ExternalWeak: {
|
|
assert(catG == ExternalWeak);
|
|
|
|
// Make them both thunks to the same internal function.
|
|
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
|
|
Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "",
|
|
F->getParent());
|
|
H->copyAttributesFrom(F);
|
|
H->takeName(F);
|
|
F->replaceAllUsesWith(H);
|
|
|
|
ThunkGToF(F, G);
|
|
ThunkGToF(F, H);
|
|
|
|
F->setLinkage(GlobalValue::InternalLinkage);
|
|
} break;
|
|
|
|
case Internal:
|
|
switch (catG) {
|
|
case ExternalStrong:
|
|
llvm_unreachable(0);
|
|
// fall-through
|
|
case ExternalWeak:
|
|
if (F->hasAddressTaken())
|
|
ThunkGToF(F, G);
|
|
else
|
|
AliasGToF(F, G);
|
|
break;
|
|
case Internal: {
|
|
bool addrTakenF = F->hasAddressTaken();
|
|
bool addrTakenG = G->hasAddressTaken();
|
|
if (!addrTakenF && addrTakenG) {
|
|
std::swap(FnVec[i], FnVec[j]);
|
|
std::swap(F, G);
|
|
std::swap(addrTakenF, addrTakenG);
|
|
}
|
|
|
|
if (addrTakenF && addrTakenG) {
|
|
ThunkGToF(F, G);
|
|
} else {
|
|
assert(!addrTakenG);
|
|
AliasGToF(F, G);
|
|
}
|
|
} break;
|
|
}
|
|
break;
|
|
}
|
|
|
|
++NumFunctionsMerged;
|
|
return true;
|
|
}
|
|
|
|
// ===----------------------------------------------------------------------===
|
|
// Pass definition
|
|
// ===----------------------------------------------------------------------===
|
|
|
|
bool MergeFunctions::runOnModule(Module &M) {
|
|
bool Changed = false;
|
|
|
|
std::map<unsigned long, std::vector<Function *> > FnMap;
|
|
|
|
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
|
|
if (F->isDeclaration() || F->isIntrinsic())
|
|
continue;
|
|
|
|
FnMap[hash(F)].push_back(F);
|
|
}
|
|
|
|
// TODO: instead of running in a loop, we could also fold functions in
|
|
// callgraph order. Constructing the CFG probably isn't cheaper than just
|
|
// running in a loop, unless it happened to already be available.
|
|
|
|
bool LocalChanged;
|
|
do {
|
|
LocalChanged = false;
|
|
DEBUG(dbgs() << "size: " << FnMap.size() << "\n");
|
|
for (std::map<unsigned long, std::vector<Function *> >::iterator
|
|
I = FnMap.begin(), E = FnMap.end(); I != E; ++I) {
|
|
std::vector<Function *> &FnVec = I->second;
|
|
DEBUG(dbgs() << "hash (" << I->first << "): " << FnVec.size() << "\n");
|
|
|
|
for (int i = 0, e = FnVec.size(); i != e; ++i) {
|
|
for (int j = i + 1; j != e; ++j) {
|
|
bool isEqual = equals(FnVec[i], FnVec[j]);
|
|
|
|
DEBUG(dbgs() << " " << FnVec[i]->getName()
|
|
<< (isEqual ? " == " : " != ")
|
|
<< FnVec[j]->getName() << "\n");
|
|
|
|
if (isEqual) {
|
|
if (fold(FnVec, i, j)) {
|
|
LocalChanged = true;
|
|
FnVec.erase(FnVec.begin() + j);
|
|
--j, --e;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
}
|
|
Changed |= LocalChanged;
|
|
} while (LocalChanged);
|
|
|
|
return Changed;
|
|
}
|