mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137667 91177308-0d34-0410-b5e6-96231b3b80d8
873 lines
30 KiB
C++
873 lines
30 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. If both functions are
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// overridable, we move the functionality into a new internal function and
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// leave two overridable thunks to it.
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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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// * 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 functions.
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//
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// * switch from n^2 pair-wise comparisons to an n-way comparison for each
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// bucket.
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//
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// * be smarter about bitcasts.
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//
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// In order to fold functions, we will sometimes add either bitcast instructions
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// or bitcast constant expressions. Unfortunately, this can confound further
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// analysis since the two functions differ where one has a bitcast and the
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// other doesn't. We should learn to look through bitcasts.
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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/DenseSet.h"
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#include "llvm/ADT/FoldingSet.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/STLExtras.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/Operator.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/IRBuilder.h"
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#include "llvm/Support/ValueHandle.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetData.h"
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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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STATISTIC(NumThunksWritten, "Number of thunks generated");
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STATISTIC(NumAliasesWritten, "Number of aliases generated");
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STATISTIC(NumDoubleWeak, "Number of new functions created");
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/// Creates a hash-code for the function which is the same for any two
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/// functions that will compare equal, without looking at the instructions
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/// inside the function.
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static unsigned profileFunction(const Function *F) {
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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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namespace {
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/// ComparableFunction - A struct that pairs together functions with a
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/// TargetData so that we can keep them together as elements in the DenseSet.
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class ComparableFunction {
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public:
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static const ComparableFunction EmptyKey;
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static const ComparableFunction TombstoneKey;
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static TargetData * const LookupOnly;
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ComparableFunction(Function *Func, TargetData *TD)
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: Func(Func), Hash(profileFunction(Func)), TD(TD) {}
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Function *getFunc() const { return Func; }
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unsigned getHash() const { return Hash; }
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TargetData *getTD() const { return TD; }
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// Drops AssertingVH reference to the function. Outside of debug mode, this
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// does nothing.
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void release() {
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assert(Func &&
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"Attempted to release function twice, or release empty/tombstone!");
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Func = NULL;
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}
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private:
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explicit ComparableFunction(unsigned Hash)
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: Func(NULL), Hash(Hash), TD(NULL) {}
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AssertingVH<Function> Func;
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unsigned Hash;
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TargetData *TD;
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};
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const ComparableFunction ComparableFunction::EmptyKey = ComparableFunction(0);
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const ComparableFunction ComparableFunction::TombstoneKey =
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ComparableFunction(1);
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TargetData *const ComparableFunction::LookupOnly = (TargetData*)(-1);
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}
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namespace llvm {
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template <>
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struct DenseMapInfo<ComparableFunction> {
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static ComparableFunction getEmptyKey() {
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return ComparableFunction::EmptyKey;
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}
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static ComparableFunction getTombstoneKey() {
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return ComparableFunction::TombstoneKey;
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}
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static unsigned getHashValue(const ComparableFunction &CF) {
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return CF.getHash();
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}
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static bool isEqual(const ComparableFunction &LHS,
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const ComparableFunction &RHS);
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};
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}
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namespace {
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/// FunctionComparator - Compares two functions to determine whether or not
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/// they will generate machine code with the same behaviour. TargetData is
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/// used if available. The comparator always fails conservatively (erring on the
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/// side of claiming that two functions are different).
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class FunctionComparator {
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public:
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FunctionComparator(const TargetData *TD, const Function *F1,
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const Function *F2)
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: F1(F1), F2(F2), TD(TD) {}
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/// Test whether the two functions have equivalent behaviour.
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bool compare();
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private:
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/// Test whether two basic blocks have equivalent behaviour.
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bool compare(const BasicBlock *BB1, const BasicBlock *BB2);
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/// Assign or look up previously assigned numbers for the two values, and
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/// return whether the numbers are equal. Numbers are assigned in the order
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/// visited.
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bool enumerate(const Value *V1, const Value *V2);
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/// Compare two Instructions for equivalence, similar to
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/// Instruction::isSameOperationAs but with modifications to the type
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/// comparison.
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bool isEquivalentOperation(const Instruction *I1,
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const Instruction *I2) const;
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/// Compare two GEPs for equivalent pointer arithmetic.
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bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2);
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bool isEquivalentGEP(const GetElementPtrInst *GEP1,
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const GetElementPtrInst *GEP2) {
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return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2));
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}
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/// Compare two Types, treating all pointer types as equal.
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bool isEquivalentType(Type *Ty1, Type *Ty2) const;
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// The two functions undergoing comparison.
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const Function *F1, *F2;
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const TargetData *TD;
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DenseMap<const Value *, const Value *> id_map;
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DenseSet<const Value *> seen_values;
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};
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}
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// Any two pointers in the same address space are equivalent, intptr_t and
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// pointers are equivalent. Otherwise, standard type equivalence rules apply.
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bool FunctionComparator::isEquivalentType(Type *Ty1,
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Type *Ty2) const {
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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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if (TD) {
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LLVMContext &Ctx = Ty1->getContext();
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if (isa<PointerType>(Ty1) && Ty2 == TD->getIntPtrType(Ctx)) return true;
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if (isa<PointerType>(Ty2) && Ty1 == TD->getIntPtrType(Ctx)) return true;
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}
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return false;
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}
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switch (Ty1->getTypeID()) {
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default:
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llvm_unreachable("Unknown type!");
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// Fall through in Release mode.
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case Type::IntegerTyID:
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case Type::VectorTyID:
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// Ty1 == Ty2 would have returned true earlier.
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return false;
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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::PointerTyID: {
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PointerType *PTy1 = cast<PointerType>(Ty1);
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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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StructType *STy1 = cast<StructType>(Ty1);
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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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FunctionType *FTy1 = cast<FunctionType>(Ty1);
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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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ArrayType *ATy1 = cast<ArrayType>(Ty1);
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ArrayType *ATy2 = cast<ArrayType>(Ty2);
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return ATy1->getNumElements() == ATy2->getNumElements() &&
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isEquivalentType(ATy1->getElementType(), ATy2->getElementType());
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}
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}
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}
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// Determine whether the two operations are the same except that pointer-to-A
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// and pointer-to-B are equivalent. This should be kept in sync with
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// Instruction::isSameOperationAs.
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bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
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const Instruction *I2) const {
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// Differences from Instruction::isSameOperationAs:
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// * replace type comparison with calls to isEquivalentType.
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// * we test for I->hasSameSubclassOptionalData (nuw/nsw/tail) at the top
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// * because of the above, we don't test for the tail bit on calls later on
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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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LI->getOrdering() == cast<LoadInst>(I2)->getOrdering() &&
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LI->getSynchScope() == cast<LoadInst>(I2)->getSynchScope();
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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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SI->getOrdering() == cast<StoreInst>(I2)->getOrdering() &&
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SI->getSynchScope() == cast<StoreInst>(I2)->getSynchScope();
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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->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
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CI->getAttributes() == cast<CallInst>(I2)->getAttributes();
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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() == cast<InvokeInst>(I2)->getAttributes();
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if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1))
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return IVI->getIndices() == cast<InsertValueInst>(I2)->getIndices();
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if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1))
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return EVI->getIndices() == cast<ExtractValueInst>(I2)->getIndices();
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if (const FenceInst *FI = dyn_cast<FenceInst>(I1))
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return FI->getOrdering() == cast<FenceInst>(I2)->getOrdering() &&
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FI->getSynchScope() == cast<FenceInst>(I2)->getSynchScope();
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if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(I1))
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return CXI->isVolatile() == cast<AtomicCmpXchgInst>(I2)->isVolatile() &&
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CXI->getOrdering() == cast<AtomicCmpXchgInst>(I2)->getOrdering() &&
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CXI->getSynchScope() == cast<AtomicCmpXchgInst>(I2)->getSynchScope();
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if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I1))
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return RMWI->getOperation() == cast<AtomicRMWInst>(I2)->getOperation() &&
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RMWI->isVolatile() == cast<AtomicRMWInst>(I2)->isVolatile() &&
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RMWI->getOrdering() == cast<AtomicRMWInst>(I2)->getOrdering() &&
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RMWI->getSynchScope() == cast<AtomicRMWInst>(I2)->getSynchScope();
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return true;
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}
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// Determine whether two GEP operations perform the same underlying arithmetic.
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bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1,
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const GEPOperator *GEP2) {
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// When we have target data, we can reduce the GEP down to the value in bytes
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// added to the address.
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if (TD && GEP1->hasAllConstantIndices() && GEP2->hasAllConstantIndices()) {
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SmallVector<Value *, 8> Indices1(GEP1->idx_begin(), GEP1->idx_end());
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SmallVector<Value *, 8> Indices2(GEP2->idx_begin(), GEP2->idx_end());
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uint64_t Offset1 = TD->getIndexedOffset(GEP1->getPointerOperandType(),
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Indices1);
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uint64_t Offset2 = TD->getIndexedOffset(GEP2->getPointerOperandType(),
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Indices2);
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return Offset1 == Offset2;
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}
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if (GEP1->getPointerOperand()->getType() !=
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GEP2->getPointerOperand()->getType())
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return false;
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if (GEP1->getNumOperands() != GEP2->getNumOperands())
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return false;
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for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) {
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if (!enumerate(GEP1->getOperand(i), GEP2->getOperand(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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// Compare two values used by the two functions under pair-wise comparison. If
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// this is the first time the values are seen, they're added to the mapping so
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// that we will detect mismatches on next use.
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bool FunctionComparator::enumerate(const Value *V1, const Value *V2) {
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// Check for function @f1 referring to itself and function @f2 referring to
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// itself, or referring to each other, or both referring to either of them.
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// They're all equivalent if the two functions are otherwise equivalent.
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if (V1 == F1 && V2 == F2)
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return true;
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if (V1 == F2 && V2 == F1)
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return true;
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if (const Constant *C1 = dyn_cast<Constant>(V1)) {
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if (V1 == V2) return true;
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const Constant *C2 = dyn_cast<Constant>(V2);
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if (!C2) return false;
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// TODO: constant expressions with GEP or references to F1 or F2.
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if (C1->isNullValue() && C2->isNullValue() &&
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isEquivalentType(C1->getType(), C2->getType()))
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return true;
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// Try bitcasting C2 to C1's type. If the bitcast is legal and returns C1
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// then they must have equal bit patterns.
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return C1->getType()->canLosslesslyBitCastTo(C2->getType()) &&
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C1 == ConstantExpr::getBitCast(const_cast<Constant*>(C2), C1->getType());
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}
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if (isa<InlineAsm>(V1) || isa<InlineAsm>(V2))
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return V1 == V2;
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// Check that V1 maps to V2. If we find a value that V1 maps to then we simply
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// check whether it's equal to V2. When there is no mapping then we need to
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// ensure that V2 isn't already equivalent to something else. For this
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// purpose, we track the V2 values in a set.
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const Value *&map_elem = id_map[V1];
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if (map_elem)
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return map_elem == V2;
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if (!seen_values.insert(V2).second)
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return false;
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map_elem = V2;
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return true;
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}
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// Test whether two basic blocks have equivalent behaviour.
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bool FunctionComparator::compare(const BasicBlock *BB1, const BasicBlock *BB2) {
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BasicBlock::const_iterator F1I = BB1->begin(), F1E = BB1->end();
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BasicBlock::const_iterator F2I = BB2->begin(), F2E = BB2->end();
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do {
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if (!enumerate(F1I, F2I))
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return false;
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if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) {
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const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I);
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if (!GEP2)
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return false;
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if (!enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
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return false;
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if (!isEquivalentGEP(GEP1, GEP2))
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return false;
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} else {
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if (!isEquivalentOperation(F1I, F2I))
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return false;
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assert(F1I->getNumOperands() == F2I->getNumOperands());
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for (unsigned i = 0, e = F1I->getNumOperands(); i != e; ++i) {
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Value *OpF1 = F1I->getOperand(i);
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Value *OpF2 = F2I->getOperand(i);
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if (!enumerate(OpF1, OpF2))
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return false;
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if (OpF1->getValueID() != OpF2->getValueID() ||
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!isEquivalentType(OpF1->getType(), OpF2->getType()))
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|
return false;
|
|
}
|
|
}
|
|
|
|
++F1I, ++F2I;
|
|
} while (F1I != F1E && F2I != F2E);
|
|
|
|
return F1I == F1E && F2I == F2E;
|
|
}
|
|
|
|
// Test whether the two functions have equivalent behaviour.
|
|
bool FunctionComparator::compare() {
|
|
// We need to recheck everything, but check the things that weren't included
|
|
// in the hash first.
|
|
|
|
if (F1->getAttributes() != F2->getAttributes())
|
|
return false;
|
|
|
|
if (F1->hasGC() != F2->hasGC())
|
|
return false;
|
|
|
|
if (F1->hasGC() && F1->getGC() != F2->getGC())
|
|
return false;
|
|
|
|
if (F1->hasSection() != F2->hasSection())
|
|
return false;
|
|
|
|
if (F1->hasSection() && F1->getSection() != F2->getSection())
|
|
return false;
|
|
|
|
if (F1->isVarArg() != F2->isVarArg())
|
|
return false;
|
|
|
|
// TODO: if it's internal and only used in direct calls, we could handle this
|
|
// case too.
|
|
if (F1->getCallingConv() != F2->getCallingConv())
|
|
return false;
|
|
|
|
if (!isEquivalentType(F1->getFunctionType(), F2->getFunctionType()))
|
|
return false;
|
|
|
|
assert(F1->arg_size() == F2->arg_size() &&
|
|
"Identically typed functions have different numbers of args!");
|
|
|
|
// Visit the arguments so that they get enumerated in the order they're
|
|
// passed in.
|
|
for (Function::const_arg_iterator f1i = F1->arg_begin(),
|
|
f2i = F2->arg_begin(), f1e = F1->arg_end(); f1i != f1e; ++f1i, ++f2i) {
|
|
if (!enumerate(f1i, f2i))
|
|
llvm_unreachable("Arguments repeat!");
|
|
}
|
|
|
|
// We do a CFG-ordered walk since the actual ordering of the blocks in the
|
|
// linked list is immaterial. Our walk starts at the entry block for both
|
|
// functions, then takes each block from each terminator in order. As an
|
|
// artifact, this also means that unreachable blocks are ignored.
|
|
SmallVector<const BasicBlock *, 8> F1BBs, F2BBs;
|
|
SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1.
|
|
|
|
F1BBs.push_back(&F1->getEntryBlock());
|
|
F2BBs.push_back(&F2->getEntryBlock());
|
|
|
|
VisitedBBs.insert(F1BBs[0]);
|
|
while (!F1BBs.empty()) {
|
|
const BasicBlock *F1BB = F1BBs.pop_back_val();
|
|
const BasicBlock *F2BB = F2BBs.pop_back_val();
|
|
|
|
if (!enumerate(F1BB, F2BB) || !compare(F1BB, F2BB))
|
|
return false;
|
|
|
|
const TerminatorInst *F1TI = F1BB->getTerminator();
|
|
const TerminatorInst *F2TI = F2BB->getTerminator();
|
|
|
|
assert(F1TI->getNumSuccessors() == F2TI->getNumSuccessors());
|
|
for (unsigned i = 0, e = F1TI->getNumSuccessors(); i != e; ++i) {
|
|
if (!VisitedBBs.insert(F1TI->getSuccessor(i)))
|
|
continue;
|
|
|
|
F1BBs.push_back(F1TI->getSuccessor(i));
|
|
F2BBs.push_back(F2TI->getSuccessor(i));
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
namespace {
|
|
|
|
/// MergeFunctions finds functions which will generate identical machine code,
|
|
/// by considering all pointer types to be equivalent. Once identified,
|
|
/// MergeFunctions will fold them by replacing a call to one to a call to a
|
|
/// bitcast of the other.
|
|
///
|
|
class MergeFunctions : public ModulePass {
|
|
public:
|
|
static char ID;
|
|
MergeFunctions()
|
|
: ModulePass(ID), HasGlobalAliases(false) {
|
|
initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnModule(Module &M);
|
|
|
|
private:
|
|
typedef DenseSet<ComparableFunction> FnSetType;
|
|
|
|
/// A work queue of functions that may have been modified and should be
|
|
/// analyzed again.
|
|
std::vector<WeakVH> Deferred;
|
|
|
|
/// Insert a ComparableFunction into the FnSet, or merge it away if it's
|
|
/// equal to one that's already present.
|
|
bool insert(ComparableFunction &NewF);
|
|
|
|
/// Remove a Function from the FnSet and queue it up for a second sweep of
|
|
/// analysis.
|
|
void remove(Function *F);
|
|
|
|
/// Find the functions that use this Value and remove them from FnSet and
|
|
/// queue the functions.
|
|
void removeUsers(Value *V);
|
|
|
|
/// Replace all direct calls of Old with calls of New. Will bitcast New if
|
|
/// necessary to make types match.
|
|
void replaceDirectCallers(Function *Old, Function *New);
|
|
|
|
/// Merge two equivalent functions. Upon completion, G may be deleted, or may
|
|
/// be converted into a thunk. In either case, it should never be visited
|
|
/// again.
|
|
void mergeTwoFunctions(Function *F, Function *G);
|
|
|
|
/// Replace G with a thunk or an alias to F. Deletes G.
|
|
void writeThunkOrAlias(Function *F, Function *G);
|
|
|
|
/// Replace G with a simple tail call to bitcast(F). Also replace direct uses
|
|
/// of G with bitcast(F). Deletes G.
|
|
void writeThunk(Function *F, Function *G);
|
|
|
|
/// Replace G with an alias to F. Deletes G.
|
|
void writeAlias(Function *F, Function *G);
|
|
|
|
/// The set of all distinct functions. Use the insert() and remove() methods
|
|
/// to modify it.
|
|
FnSetType FnSet;
|
|
|
|
/// TargetData for more accurate GEP comparisons. May be NULL.
|
|
TargetData *TD;
|
|
|
|
/// Whether or not the target supports global aliases.
|
|
bool HasGlobalAliases;
|
|
};
|
|
|
|
} // end anonymous namespace
|
|
|
|
char MergeFunctions::ID = 0;
|
|
INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)
|
|
|
|
ModulePass *llvm::createMergeFunctionsPass() {
|
|
return new MergeFunctions();
|
|
}
|
|
|
|
bool MergeFunctions::runOnModule(Module &M) {
|
|
bool Changed = false;
|
|
TD = getAnalysisIfAvailable<TargetData>();
|
|
|
|
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
|
|
if (!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
|
|
Deferred.push_back(WeakVH(I));
|
|
}
|
|
FnSet.resize(Deferred.size());
|
|
|
|
do {
|
|
std::vector<WeakVH> Worklist;
|
|
Deferred.swap(Worklist);
|
|
|
|
DEBUG(dbgs() << "size of module: " << M.size() << '\n');
|
|
DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n');
|
|
|
|
// Insert only strong functions and merge them. Strong function merging
|
|
// always deletes one of them.
|
|
for (std::vector<WeakVH>::iterator I = Worklist.begin(),
|
|
E = Worklist.end(); I != E; ++I) {
|
|
if (!*I) continue;
|
|
Function *F = cast<Function>(*I);
|
|
if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
|
|
!F->mayBeOverridden()) {
|
|
ComparableFunction CF = ComparableFunction(F, TD);
|
|
Changed |= insert(CF);
|
|
}
|
|
}
|
|
|
|
// Insert only weak functions and merge them. By doing these second we
|
|
// create thunks to the strong function when possible. When two weak
|
|
// functions are identical, we create a new strong function with two weak
|
|
// weak thunks to it which are identical but not mergable.
|
|
for (std::vector<WeakVH>::iterator I = Worklist.begin(),
|
|
E = Worklist.end(); I != E; ++I) {
|
|
if (!*I) continue;
|
|
Function *F = cast<Function>(*I);
|
|
if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
|
|
F->mayBeOverridden()) {
|
|
ComparableFunction CF = ComparableFunction(F, TD);
|
|
Changed |= insert(CF);
|
|
}
|
|
}
|
|
DEBUG(dbgs() << "size of FnSet: " << FnSet.size() << '\n');
|
|
} while (!Deferred.empty());
|
|
|
|
FnSet.clear();
|
|
|
|
return Changed;
|
|
}
|
|
|
|
bool DenseMapInfo<ComparableFunction>::isEqual(const ComparableFunction &LHS,
|
|
const ComparableFunction &RHS) {
|
|
if (LHS.getFunc() == RHS.getFunc() &&
|
|
LHS.getHash() == RHS.getHash())
|
|
return true;
|
|
if (!LHS.getFunc() || !RHS.getFunc())
|
|
return false;
|
|
|
|
// One of these is a special "underlying pointer comparison only" object.
|
|
if (LHS.getTD() == ComparableFunction::LookupOnly ||
|
|
RHS.getTD() == ComparableFunction::LookupOnly)
|
|
return false;
|
|
|
|
assert(LHS.getTD() == RHS.getTD() &&
|
|
"Comparing functions for different targets");
|
|
|
|
return FunctionComparator(LHS.getTD(), LHS.getFunc(),
|
|
RHS.getFunc()).compare();
|
|
}
|
|
|
|
// Replace direct callers of Old with New.
|
|
void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
|
|
Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
|
|
for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
|
|
UI != UE;) {
|
|
Value::use_iterator TheIter = UI;
|
|
++UI;
|
|
CallSite CS(*TheIter);
|
|
if (CS && CS.isCallee(TheIter)) {
|
|
remove(CS.getInstruction()->getParent()->getParent());
|
|
TheIter.getUse().set(BitcastNew);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Replace G with an alias to F if possible, or else a thunk to F. Deletes G.
|
|
void MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
|
|
if (HasGlobalAliases && G->hasUnnamedAddr()) {
|
|
if (G->hasExternalLinkage() || G->hasLocalLinkage() ||
|
|
G->hasWeakLinkage()) {
|
|
writeAlias(F, G);
|
|
return;
|
|
}
|
|
}
|
|
|
|
writeThunk(F, G);
|
|
}
|
|
|
|
// Replace G with a simple tail call to bitcast(F). Also replace direct uses
|
|
// of G with bitcast(F). Deletes G.
|
|
void MergeFunctions::writeThunk(Function *F, Function *G) {
|
|
if (!G->mayBeOverridden()) {
|
|
// Redirect direct callers of G to F.
|
|
replaceDirectCallers(G, F);
|
|
}
|
|
|
|
// If G was internal then we may have replaced all uses of G with F. If so,
|
|
// stop here and delete G. There's no need for a thunk.
|
|
if (G->hasLocalLinkage() && G->use_empty()) {
|
|
G->eraseFromParent();
|
|
return;
|
|
}
|
|
|
|
Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
|
|
G->getParent());
|
|
BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
|
|
IRBuilder<false> Builder(BB);
|
|
|
|
SmallVector<Value *, 16> Args;
|
|
unsigned i = 0;
|
|
FunctionType *FFTy = F->getFunctionType();
|
|
for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end();
|
|
AI != AE; ++AI) {
|
|
Args.push_back(Builder.CreateBitCast(AI, FFTy->getParamType(i)));
|
|
++i;
|
|
}
|
|
|
|
CallInst *CI = Builder.CreateCall(F, Args);
|
|
CI->setTailCall();
|
|
CI->setCallingConv(F->getCallingConv());
|
|
if (NewG->getReturnType()->isVoidTy()) {
|
|
Builder.CreateRetVoid();
|
|
} else {
|
|
Builder.CreateRet(Builder.CreateBitCast(CI, NewG->getReturnType()));
|
|
}
|
|
|
|
NewG->copyAttributesFrom(G);
|
|
NewG->takeName(G);
|
|
removeUsers(G);
|
|
G->replaceAllUsesWith(NewG);
|
|
G->eraseFromParent();
|
|
|
|
DEBUG(dbgs() << "writeThunk: " << NewG->getName() << '\n');
|
|
++NumThunksWritten;
|
|
}
|
|
|
|
// Replace G with an alias to F and delete G.
|
|
void MergeFunctions::writeAlias(Function *F, Function *G) {
|
|
Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
|
|
GlobalAlias *GA = new GlobalAlias(G->getType(), G->getLinkage(), "",
|
|
BitcastF, G->getParent());
|
|
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
|
|
GA->takeName(G);
|
|
GA->setVisibility(G->getVisibility());
|
|
removeUsers(G);
|
|
G->replaceAllUsesWith(GA);
|
|
G->eraseFromParent();
|
|
|
|
DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n');
|
|
++NumAliasesWritten;
|
|
}
|
|
|
|
// Merge two equivalent functions. Upon completion, Function G is deleted.
|
|
void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
|
|
if (F->mayBeOverridden()) {
|
|
assert(G->mayBeOverridden());
|
|
|
|
if (HasGlobalAliases) {
|
|
// Make them both thunks to the same internal function.
|
|
Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "",
|
|
F->getParent());
|
|
H->copyAttributesFrom(F);
|
|
H->takeName(F);
|
|
removeUsers(F);
|
|
F->replaceAllUsesWith(H);
|
|
|
|
unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
|
|
|
|
writeAlias(F, G);
|
|
writeAlias(F, H);
|
|
|
|
F->setAlignment(MaxAlignment);
|
|
F->setLinkage(GlobalValue::PrivateLinkage);
|
|
} else {
|
|
// We can't merge them. Instead, pick one and update all direct callers
|
|
// to call it and hope that we improve the instruction cache hit rate.
|
|
replaceDirectCallers(G, F);
|
|
}
|
|
|
|
++NumDoubleWeak;
|
|
} else {
|
|
writeThunkOrAlias(F, G);
|
|
}
|
|
|
|
++NumFunctionsMerged;
|
|
}
|
|
|
|
// Insert a ComparableFunction into the FnSet, or merge it away if equal to one
|
|
// that was already inserted.
|
|
bool MergeFunctions::insert(ComparableFunction &NewF) {
|
|
std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF);
|
|
if (Result.second) {
|
|
DEBUG(dbgs() << "Inserting as unique: " << NewF.getFunc()->getName() << '\n');
|
|
return false;
|
|
}
|
|
|
|
const ComparableFunction &OldF = *Result.first;
|
|
|
|
// Never thunk a strong function to a weak function.
|
|
assert(!OldF.getFunc()->mayBeOverridden() ||
|
|
NewF.getFunc()->mayBeOverridden());
|
|
|
|
DEBUG(dbgs() << " " << OldF.getFunc()->getName() << " == "
|
|
<< NewF.getFunc()->getName() << '\n');
|
|
|
|
Function *DeleteF = NewF.getFunc();
|
|
NewF.release();
|
|
mergeTwoFunctions(OldF.getFunc(), DeleteF);
|
|
return true;
|
|
}
|
|
|
|
// Remove a function from FnSet. If it was already in FnSet, add it to Deferred
|
|
// so that we'll look at it in the next round.
|
|
void MergeFunctions::remove(Function *F) {
|
|
// We need to make sure we remove F, not a function "equal" to F per the
|
|
// function equality comparator.
|
|
//
|
|
// The special "lookup only" ComparableFunction bypasses the expensive
|
|
// function comparison in favour of a pointer comparison on the underlying
|
|
// Function*'s.
|
|
ComparableFunction CF = ComparableFunction(F, ComparableFunction::LookupOnly);
|
|
if (FnSet.erase(CF)) {
|
|
DEBUG(dbgs() << "Removed " << F->getName() << " from set and deferred it.\n");
|
|
Deferred.push_back(F);
|
|
}
|
|
}
|
|
|
|
// For each instruction used by the value, remove() the function that contains
|
|
// the instruction. This should happen right before a call to RAUW.
|
|
void MergeFunctions::removeUsers(Value *V) {
|
|
std::vector<Value *> Worklist;
|
|
Worklist.push_back(V);
|
|
while (!Worklist.empty()) {
|
|
Value *V = Worklist.back();
|
|
Worklist.pop_back();
|
|
|
|
for (Value::use_iterator UI = V->use_begin(), UE = V->use_end();
|
|
UI != UE; ++UI) {
|
|
Use &U = UI.getUse();
|
|
if (Instruction *I = dyn_cast<Instruction>(U.getUser())) {
|
|
remove(I->getParent()->getParent());
|
|
} else if (isa<GlobalValue>(U.getUser())) {
|
|
// do nothing
|
|
} else if (Constant *C = dyn_cast<Constant>(U.getUser())) {
|
|
for (Value::use_iterator CUI = C->use_begin(), CUE = C->use_end();
|
|
CUI != CUE; ++CUI)
|
|
Worklist.push_back(*CUI);
|
|
}
|
|
}
|
|
}
|
|
}
|