llvm-project/llvm/lib/Transforms/IPO/MergeFunctions.cpp

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//===- MergeFunctions.cpp - Merge identical functions ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass looks for equivalent functions that are mergable and folds them.
//
// A hash is computed from the function, based on its type and number of
// basic blocks.
//
// Once all hashes are computed, we perform an expensive equality comparison
// on each function pair. This takes n^2/2 comparisons per bucket, so it's
// important that the hash function be high quality. The equality comparison
// iterates through each instruction in each basic block.
//
// When a match is found the functions are folded. If both functions are
// overridable, we move the functionality into a new internal function and
// leave two overridable thunks to it.
//
//===----------------------------------------------------------------------===//
//
// Future work:
//
// * virtual functions.
//
// Many functions have their address taken by the virtual function table for
// the object they belong to. However, as long as it's only used for a lookup
// and call, this is irrelevant, and we'd like to fold such functions.
//
// * switch from n^2 pair-wise comparisons to an n-way comparison for each
// bucket.
//
// * be smarter about bitcasts.
//
// In order to fold functions, we will sometimes add either bitcast instructions
// or bitcast constant expressions. Unfortunately, this can confound further
// analysis since the two functions differ where one has a bitcast and the
// other doesn't. We should learn to look through bitcasts.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "mergefunc"
STATISTIC(NumFunctionsMerged, "Number of functions merged");
STATISTIC(NumThunksWritten, "Number of thunks generated");
STATISTIC(NumAliasesWritten, "Number of aliases generated");
STATISTIC(NumDoubleWeak, "Number of new functions created");
/// Returns the type id for a type to be hashed. We turn pointer types into
/// integers here because the actual compare logic below considers pointers and
/// integers of the same size as equal.
static Type::TypeID getTypeIDForHash(Type *Ty) {
if (Ty->isPointerTy())
return Type::IntegerTyID;
return Ty->getTypeID();
}
/// Creates a hash-code for the function which is the same for any two
/// functions that will compare equal, without looking at the instructions
/// inside the function.
static unsigned profileFunction(const Function *F) {
FunctionType *FTy = F->getFunctionType();
FoldingSetNodeID ID;
ID.AddInteger(F->size());
ID.AddInteger(F->getCallingConv());
ID.AddBoolean(F->hasGC());
ID.AddBoolean(FTy->isVarArg());
ID.AddInteger(getTypeIDForHash(FTy->getReturnType()));
for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
ID.AddInteger(getTypeIDForHash(FTy->getParamType(i)));
return ID.ComputeHash();
}
namespace {
/// ComparableFunction - A struct that pairs together functions with a
/// DataLayout so that we can keep them together as elements in the DenseSet.
class ComparableFunction {
public:
static const ComparableFunction EmptyKey;
static const ComparableFunction TombstoneKey;
static DataLayout * const LookupOnly;
ComparableFunction(Function *Func, const DataLayout *DL)
: Func(Func), Hash(profileFunction(Func)), DL(DL) {}
Function *getFunc() const { return Func; }
unsigned getHash() const { return Hash; }
const DataLayout *getDataLayout() const { return DL; }
// Drops AssertingVH reference to the function. Outside of debug mode, this
// does nothing.
void release() {
assert(Func &&
"Attempted to release function twice, or release empty/tombstone!");
Func = nullptr;
}
private:
explicit ComparableFunction(unsigned Hash)
: Func(nullptr), Hash(Hash), DL(nullptr) {}
AssertingVH<Function> Func;
unsigned Hash;
const DataLayout *DL;
};
const ComparableFunction ComparableFunction::EmptyKey = ComparableFunction(0);
const ComparableFunction ComparableFunction::TombstoneKey =
ComparableFunction(1);
DataLayout *const ComparableFunction::LookupOnly = (DataLayout*)(-1);
}
namespace llvm {
template <>
struct DenseMapInfo<ComparableFunction> {
static ComparableFunction getEmptyKey() {
return ComparableFunction::EmptyKey;
}
static ComparableFunction getTombstoneKey() {
return ComparableFunction::TombstoneKey;
}
static unsigned getHashValue(const ComparableFunction &CF) {
return CF.getHash();
}
static bool isEqual(const ComparableFunction &LHS,
const ComparableFunction &RHS);
};
}
namespace {
/// FunctionComparator - Compares two functions to determine whether or not
/// they will generate machine code with the same behaviour. DataLayout is
/// used if available. The comparator always fails conservatively (erring on the
/// side of claiming that two functions are different).
class FunctionComparator {
public:
FunctionComparator(const DataLayout *DL, const Function *F1,
const Function *F2)
: F1(F1), F2(F2), DL(DL) {}
/// Test whether the two functions have equivalent behaviour.
bool compare();
private:
/// Test whether two basic blocks have equivalent behaviour.
bool compare(const BasicBlock *BB1, const BasicBlock *BB2);
/// Constants comparison.
/// Its analog to lexicographical comparison between hypothetical numbers
/// of next format:
/// <bitcastability-trait><raw-bit-contents>
///
/// 1. Bitcastability.
/// Check whether L's type could be losslessly bitcasted to R's type.
/// On this stage method, in case when lossless bitcast is not possible
/// method returns -1 or 1, thus also defining which type is greater in
/// context of bitcastability.
/// Stage 0: If types are equal in terms of cmpTypes, then we can go straight
/// to the contents comparison.
/// If types differ, remember types comparison result and check
/// whether we still can bitcast types.
/// Stage 1: Types that satisfies isFirstClassType conditions are always
/// greater then others.
/// Stage 2: Vector is greater then non-vector.
/// If both types are vectors, then vector with greater bitwidth is
/// greater.
/// If both types are vectors with the same bitwidth, then types
/// are bitcastable, and we can skip other stages, and go to contents
/// comparison.
/// Stage 3: Pointer types are greater than non-pointers. If both types are
/// pointers of the same address space - go to contents comparison.
/// Different address spaces: pointer with greater address space is
/// greater.
/// Stage 4: Types are neither vectors, nor pointers. And they differ.
/// We don't know how to bitcast them. So, we better don't do it,
/// and return types comparison result (so it determines the
/// relationship among constants we don't know how to bitcast).
///
/// Just for clearance, let's see how the set of constants could look
/// on single dimension axis:
///
/// [NFCT], [FCT, "others"], [FCT, pointers], [FCT, vectors]
/// Where: NFCT - Not a FirstClassType
/// FCT - FirstClassTyp:
///
/// 2. Compare raw contents.
/// It ignores types on this stage and only compares bits from L and R.
/// Returns 0, if L and R has equivalent contents.
/// -1 or 1 if values are different.
/// Pretty trivial:
/// 2.1. If contents are numbers, compare numbers.
/// Ints with greater bitwidth are greater. Ints with same bitwidths
/// compared by their contents.
/// 2.2. "And so on". Just to avoid discrepancies with comments
/// perhaps it would be better to read the implementation itself.
/// 3. And again about overall picture. Let's look back at how the ordered set
/// of constants will look like:
/// [NFCT], [FCT, "others"], [FCT, pointers], [FCT, vectors]
///
/// Now look, what could be inside [FCT, "others"], for example:
/// [FCT, "others"] =
/// [
/// [double 0.1], [double 1.23],
/// [i32 1], [i32 2],
/// { double 1.0 }, ; StructTyID, NumElements = 1
/// { i32 1 }, ; StructTyID, NumElements = 1
/// { double 1, i32 1 }, ; StructTyID, NumElements = 2
/// { i32 1, double 1 } ; StructTyID, NumElements = 2
/// ]
///
/// Let's explain the order. Float numbers will be less than integers, just
/// because of cmpType terms: FloatTyID < IntegerTyID.
/// Floats (with same fltSemantics) are sorted according to their value.
/// Then you can see integers, and they are, like a floats,
/// could be easy sorted among each others.
/// The structures. Structures are grouped at the tail, again because of their
/// TypeID: StructTyID > IntegerTyID > FloatTyID.
/// Structures with greater number of elements are greater. Structures with
/// greater elements going first are greater.
/// The same logic with vectors, arrays and other possible complex types.
///
/// Bitcastable constants.
/// Let's assume, that some constant, belongs to some group of
/// "so-called-equal" values with different types, and at the same time
/// belongs to another group of constants with equal types
/// and "really" equal values.
///
/// Now, prove that this is impossible:
///
/// If constant A with type TyA is bitcastable to B with type TyB, then:
/// 1. All constants with equal types to TyA, are bitcastable to B. Since
/// those should be vectors (if TyA is vector), pointers
/// (if TyA is pointer), or else (if TyA equal to TyB), those types should
/// be equal to TyB.
/// 2. All constants with non-equal, but bitcastable types to TyA, are
/// bitcastable to B.
/// Once again, just because we allow it to vectors and pointers only.
/// This statement could be expanded as below:
/// 2.1. All vectors with equal bitwidth to vector A, has equal bitwidth to
/// vector B, and thus bitcastable to B as well.
/// 2.2. All pointers of the same address space, no matter what they point to,
/// bitcastable. So if C is pointer, it could be bitcasted to A and to B.
/// So any constant equal or bitcastable to A is equal or bitcastable to B.
/// QED.
///
/// In another words, for pointers and vectors, we ignore top-level type and
/// look at their particular properties (bit-width for vectors, and
/// address space for pointers).
/// If these properties are equal - compare their contents.
int cmpConstants(const Constant *L, const Constant *R);
/// Assign or look up previously assigned numbers for the two values, and
/// return whether the numbers are equal. Numbers are assigned in the order
/// visited.
/// Comparison order:
/// Stage 0: Value that is function itself is always greater then others.
/// If left and right values are references to their functions, then
/// they are equal.
/// Stage 1: Constants are greater than non-constants.
/// If both left and right are constants, then the result of
/// cmpConstants is used as cmpValues result.
/// Stage 2: InlineAsm instances are greater than others. If both left and
/// right are InlineAsm instances, InlineAsm* pointers casted to
/// integers and compared as numbers.
/// Stage 3: For all other cases we compare order we meet these values in
/// their functions. If right value was met first during scanning,
/// then left value is greater.
/// In another words, we compare serial numbers, for more details
/// see comments for sn_mapL and sn_mapR.
int cmpValues(const Value *L, const Value *R);
bool enumerate(const Value *V1, const Value *V2) {
return cmpValues(V1, V2) == 0;
}
/// Compare two Instructions for equivalence, similar to
/// Instruction::isSameOperationAs but with modifications to the type
/// comparison.
bool isEquivalentOperation(const Instruction *I1,
const Instruction *I2) const;
/// Compare two GEPs for equivalent pointer arithmetic.
bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2);
bool isEquivalentGEP(const GetElementPtrInst *GEP1,
const GetElementPtrInst *GEP2) {
return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2));
}
/// cmpType - compares two types,
/// defines total ordering among the types set.
///
/// Return values:
/// 0 if types are equal,
/// -1 if Left is less than Right,
/// +1 if Left is greater than Right.
///
/// Description:
/// Comparison is broken onto stages. Like in lexicographical comparison
/// stage coming first has higher priority.
/// On each explanation stage keep in mind total ordering properties.
///
/// 0. Before comparison we coerce pointer types of 0 address space to
/// integer.
/// We also don't bother with same type at left and right, so
/// just return 0 in this case.
///
/// 1. If types are of different kind (different type IDs).
/// Return result of type IDs comparison, treating them as numbers.
/// 2. If types are vectors or integers, compare Type* values as numbers.
/// 3. Types has same ID, so check whether they belongs to the next group:
/// * Void
/// * Float
/// * Double
/// * X86_FP80
/// * FP128
/// * PPC_FP128
/// * Label
/// * Metadata
/// If so - return 0, yes - we can treat these types as equal only because
/// their IDs are same.
/// 4. If Left and Right are pointers, return result of address space
/// comparison (numbers comparison). We can treat pointer types of same
/// address space as equal.
/// 5. If types are complex.
/// Then both Left and Right are to be expanded and their element types will
/// be checked with the same way. If we get Res != 0 on some stage, return it.
/// Otherwise return 0.
/// 6. For all other cases put llvm_unreachable.
int cmpType(Type *TyL, Type *TyR) const;
bool isEquivalentType(Type *Ty1, Type *Ty2) const {
return cmpType(Ty1, Ty2) == 0;
}
int cmpNumbers(uint64_t L, uint64_t R) const;
int cmpAPInt(const APInt &L, const APInt &R) const;
int cmpAPFloat(const APFloat &L, const APFloat &R) const;
int cmpStrings(StringRef L, StringRef R) const;
int cmpAttrs(const AttributeSet L, const AttributeSet R) const;
// The two functions undergoing comparison.
const Function *F1, *F2;
const DataLayout *DL;
/// Assign serial numbers to values from left function, and values from
/// right function.
/// Explanation:
/// Being comparing functions we need to compare values we meet at left and
/// right sides.
/// Its easy to sort things out for external values. It just should be
/// the same value at left and right.
/// But for local values (those were introduced inside function body)
/// we have to ensure they were introduced at exactly the same place,
/// and plays the same role.
/// Let's assign serial number to each value when we meet it first time.
/// Values that were met at same place will be with same serial numbers.
/// In this case it would be good to explain few points about values assigned
/// to BBs and other ways of implementation (see below).
///
/// 1. Safety of BB reordering.
/// It's safe to change the order of BasicBlocks in function.
/// Relationship with other functions and serial numbering will not be
/// changed in this case.
/// As follows from FunctionComparator::compare(), we do CFG walk: we start
/// from the entry, and then take each terminator. So it doesn't matter how in
/// fact BBs are ordered in function. And since cmpValues are called during
/// this walk, the numbering depends only on how BBs located inside the CFG.
/// So the answer is - yes. We will get the same numbering.
///
/// 2. Impossibility to use dominance properties of values.
/// If we compare two instruction operands: first is usage of local
/// variable AL from function FL, and second is usage of local variable AR
/// from FR, we could compare their origins and check whether they are
/// defined at the same place.
/// But, we are still not able to compare operands of PHI nodes, since those
/// could be operands from further BBs we didn't scan yet.
/// So it's impossible to use dominance properties in general.
DenseMap<const Value*, int> sn_mapL, sn_mapR;
};
}
int FunctionComparator::cmpNumbers(uint64_t L, uint64_t R) const {
if (L < R) return -1;
if (L > R) return 1;
return 0;
}
int FunctionComparator::cmpAPInt(const APInt &L, const APInt &R) const {
if (int Res = cmpNumbers(L.getBitWidth(), R.getBitWidth()))
return Res;
if (L.ugt(R)) return 1;
if (R.ugt(L)) return -1;
return 0;
}
int FunctionComparator::cmpAPFloat(const APFloat &L, const APFloat &R) const {
if (int Res = cmpNumbers((uint64_t)&L.getSemantics(),
(uint64_t)&R.getSemantics()))
return Res;
return cmpAPInt(L.bitcastToAPInt(), R.bitcastToAPInt());
}
int FunctionComparator::cmpStrings(StringRef L, StringRef R) const {
// Prevent heavy comparison, compare sizes first.
if (int Res = cmpNumbers(L.size(), R.size()))
return Res;
// Compare strings lexicographically only when it is necessary: only when
// strings are equal in size.
return L.compare(R);
}
int FunctionComparator::cmpAttrs(const AttributeSet L,
const AttributeSet R) const {
if (int Res = cmpNumbers(L.getNumSlots(), R.getNumSlots()))
return Res;
for (unsigned i = 0, e = L.getNumSlots(); i != e; ++i) {
AttributeSet::iterator LI = L.begin(i), LE = L.end(i), RI = R.begin(i),
RE = R.end(i);
for (; LI != LE && RI != RE; ++LI, ++RI) {
Attribute LA = *LI;
Attribute RA = *RI;
if (LA < RA)
return -1;
if (RA < LA)
return 1;
}
if (LI != LE)
return 1;
if (RI != RE)
return -1;
}
return 0;
}
/// Constants comparison:
/// 1. Check whether type of L constant could be losslessly bitcasted to R
/// type.
/// 2. Compare constant contents.
/// For more details see declaration comments.
int FunctionComparator::cmpConstants(const Constant *L, const Constant *R) {
Type *TyL = L->getType();
Type *TyR = R->getType();
// Check whether types are bitcastable. This part is just re-factored
// Type::canLosslesslyBitCastTo method, but instead of returning true/false,
// we also pack into result which type is "less" for us.
int TypesRes = cmpType(TyL, TyR);
if (TypesRes != 0) {
// Types are different, but check whether we can bitcast them.
if (!TyL->isFirstClassType()) {
if (TyR->isFirstClassType())
return -1;
// Neither TyL nor TyR are values of first class type. Return the result
// of comparing the types
return TypesRes;
}
if (!TyR->isFirstClassType()) {
if (TyL->isFirstClassType())
return 1;
return TypesRes;
}
// Vector -> Vector conversions are always lossless if the two vector types
// have the same size, otherwise not.
unsigned TyLWidth = 0;
unsigned TyRWidth = 0;
if (const VectorType *VecTyL = dyn_cast<VectorType>(TyL))
TyLWidth = VecTyL->getBitWidth();
if (const VectorType *VecTyR = dyn_cast<VectorType>(TyR))
TyRWidth = VecTyR->getBitWidth();
if (TyLWidth != TyRWidth)
return cmpNumbers(TyLWidth, TyRWidth);
// Zero bit-width means neither TyL nor TyR are vectors.
if (!TyLWidth) {
PointerType *PTyL = dyn_cast<PointerType>(TyL);
PointerType *PTyR = dyn_cast<PointerType>(TyR);
if (PTyL && PTyR) {
unsigned AddrSpaceL = PTyL->getAddressSpace();
unsigned AddrSpaceR = PTyR->getAddressSpace();
if (int Res = cmpNumbers(AddrSpaceL, AddrSpaceR))
return Res;
}
if (PTyL)
return 1;
if (PTyR)
return -1;
// TyL and TyR aren't vectors, nor pointers. We don't know how to
// bitcast them.
return TypesRes;
}
}
// OK, types are bitcastable, now check constant contents.
if (L->isNullValue() && R->isNullValue())
return TypesRes;
if (L->isNullValue() && !R->isNullValue())
return 1;
if (!L->isNullValue() && R->isNullValue())
return -1;
if (int Res = cmpNumbers(L->getValueID(), R->getValueID()))
return Res;
switch (L->getValueID()) {
case Value::UndefValueVal: return TypesRes;
case Value::ConstantIntVal: {
const APInt &LInt = cast<ConstantInt>(L)->getValue();
const APInt &RInt = cast<ConstantInt>(R)->getValue();
return cmpAPInt(LInt, RInt);
}
case Value::ConstantFPVal: {
const APFloat &LAPF = cast<ConstantFP>(L)->getValueAPF();
const APFloat &RAPF = cast<ConstantFP>(R)->getValueAPF();
return cmpAPFloat(LAPF, RAPF);
}
case Value::ConstantArrayVal: {
const ConstantArray *LA = cast<ConstantArray>(L);
const ConstantArray *RA = cast<ConstantArray>(R);
uint64_t NumElementsL = cast<ArrayType>(TyL)->getNumElements();
uint64_t NumElementsR = cast<ArrayType>(TyR)->getNumElements();
if (int Res = cmpNumbers(NumElementsL, NumElementsR))
return Res;
for (uint64_t i = 0; i < NumElementsL; ++i) {
if (int Res = cmpConstants(cast<Constant>(LA->getOperand(i)),
cast<Constant>(RA->getOperand(i))))
return Res;
}
return 0;
}
case Value::ConstantStructVal: {
const ConstantStruct *LS = cast<ConstantStruct>(L);
const ConstantStruct *RS = cast<ConstantStruct>(R);
unsigned NumElementsL = cast<StructType>(TyL)->getNumElements();
unsigned NumElementsR = cast<StructType>(TyR)->getNumElements();
if (int Res = cmpNumbers(NumElementsL, NumElementsR))
return Res;
for (unsigned i = 0; i != NumElementsL; ++i) {
if (int Res = cmpConstants(cast<Constant>(LS->getOperand(i)),
cast<Constant>(RS->getOperand(i))))
return Res;
}
return 0;
}
case Value::ConstantVectorVal: {
const ConstantVector *LV = cast<ConstantVector>(L);
const ConstantVector *RV = cast<ConstantVector>(R);
unsigned NumElementsL = cast<VectorType>(TyL)->getNumElements();
unsigned NumElementsR = cast<VectorType>(TyR)->getNumElements();
if (int Res = cmpNumbers(NumElementsL, NumElementsR))
return Res;
for (uint64_t i = 0; i < NumElementsL; ++i) {
if (int Res = cmpConstants(cast<Constant>(LV->getOperand(i)),
cast<Constant>(RV->getOperand(i))))
return Res;
}
return 0;
}
case Value::ConstantExprVal: {
const ConstantExpr *LE = cast<ConstantExpr>(L);
const ConstantExpr *RE = cast<ConstantExpr>(R);
unsigned NumOperandsL = LE->getNumOperands();
unsigned NumOperandsR = RE->getNumOperands();
if (int Res = cmpNumbers(NumOperandsL, NumOperandsR))
return Res;
for (unsigned i = 0; i < NumOperandsL; ++i) {
if (int Res = cmpConstants(cast<Constant>(LE->getOperand(i)),
cast<Constant>(RE->getOperand(i))))
return Res;
}
return 0;
}
case Value::FunctionVal:
case Value::GlobalVariableVal:
case Value::GlobalAliasVal:
default: // Unknown constant, cast L and R pointers to numbers and compare.
return cmpNumbers((uint64_t)L, (uint64_t)R);
}
}
/// cmpType - compares two types,
/// defines total ordering among the types set.
/// See method declaration comments for more details.
int FunctionComparator::cmpType(Type *TyL, Type *TyR) const {
PointerType *PTyL = dyn_cast<PointerType>(TyL);
PointerType *PTyR = dyn_cast<PointerType>(TyR);
if (DL) {
if (PTyL && PTyL->getAddressSpace() == 0) TyL = DL->getIntPtrType(TyL);
if (PTyR && PTyR->getAddressSpace() == 0) TyR = DL->getIntPtrType(TyR);
}
if (TyL == TyR)
return 0;
if (int Res = cmpNumbers(TyL->getTypeID(), TyR->getTypeID()))
return Res;
switch (TyL->getTypeID()) {
default:
llvm_unreachable("Unknown type!");
// Fall through in Release mode.
case Type::IntegerTyID:
case Type::VectorTyID:
// TyL == TyR would have returned true earlier.
return cmpNumbers((uint64_t)TyL, (uint64_t)TyR);
case Type::VoidTyID:
case Type::FloatTyID:
case Type::DoubleTyID:
case Type::X86_FP80TyID:
case Type::FP128TyID:
case Type::PPC_FP128TyID:
case Type::LabelTyID:
case Type::MetadataTyID:
return 0;
case Type::PointerTyID: {
assert(PTyL && PTyR && "Both types must be pointers here.");
return cmpNumbers(PTyL->getAddressSpace(), PTyR->getAddressSpace());
}
case Type::StructTyID: {
StructType *STyL = cast<StructType>(TyL);
StructType *STyR = cast<StructType>(TyR);
if (STyL->getNumElements() != STyR->getNumElements())
return cmpNumbers(STyL->getNumElements(), STyR->getNumElements());
if (STyL->isPacked() != STyR->isPacked())
return cmpNumbers(STyL->isPacked(), STyR->isPacked());
for (unsigned i = 0, e = STyL->getNumElements(); i != e; ++i) {
if (int Res = cmpType(STyL->getElementType(i),
STyR->getElementType(i)))
return Res;
}
return 0;
}
case Type::FunctionTyID: {
FunctionType *FTyL = cast<FunctionType>(TyL);
FunctionType *FTyR = cast<FunctionType>(TyR);
if (FTyL->getNumParams() != FTyR->getNumParams())
return cmpNumbers(FTyL->getNumParams(), FTyR->getNumParams());
if (FTyL->isVarArg() != FTyR->isVarArg())
return cmpNumbers(FTyL->isVarArg(), FTyR->isVarArg());
if (int Res = cmpType(FTyL->getReturnType(), FTyR->getReturnType()))
return Res;
for (unsigned i = 0, e = FTyL->getNumParams(); i != e; ++i) {
if (int Res = cmpType(FTyL->getParamType(i), FTyR->getParamType(i)))
return Res;
}
return 0;
}
case Type::ArrayTyID: {
ArrayType *ATyL = cast<ArrayType>(TyL);
ArrayType *ATyR = cast<ArrayType>(TyR);
if (ATyL->getNumElements() != ATyR->getNumElements())
return cmpNumbers(ATyL->getNumElements(), ATyR->getNumElements());
return cmpType(ATyL->getElementType(), ATyR->getElementType());
}
}
}
// Determine whether the two operations are the same except that pointer-to-A
// and pointer-to-B are equivalent. This should be kept in sync with
// Instruction::isSameOperationAs.
bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
const Instruction *I2) const {
// Differences from Instruction::isSameOperationAs:
// * replace type comparison with calls to isEquivalentType.
// * we test for I->hasSameSubclassOptionalData (nuw/nsw/tail) at the top
// * because of the above, we don't test for the tail bit on calls later on
if (I1->getOpcode() != I2->getOpcode() ||
I1->getNumOperands() != I2->getNumOperands() ||
!isEquivalentType(I1->getType(), I2->getType()) ||
!I1->hasSameSubclassOptionalData(I2))
return false;
// We have two instructions of identical opcode and #operands. Check to see
// if all operands are the same type
for (unsigned i = 0, e = I1->getNumOperands(); i != e; ++i)
if (!isEquivalentType(I1->getOperand(i)->getType(),
I2->getOperand(i)->getType()))
return false;
// Check special state that is a part of some instructions.
if (const LoadInst *LI = dyn_cast<LoadInst>(I1))
return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() &&
LI->getAlignment() == cast<LoadInst>(I2)->getAlignment() &&
LI->getOrdering() == cast<LoadInst>(I2)->getOrdering() &&
LI->getSynchScope() == cast<LoadInst>(I2)->getSynchScope();
if (const StoreInst *SI = dyn_cast<StoreInst>(I1))
return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() &&
SI->getAlignment() == cast<StoreInst>(I2)->getAlignment() &&
SI->getOrdering() == cast<StoreInst>(I2)->getOrdering() &&
SI->getSynchScope() == cast<StoreInst>(I2)->getSynchScope();
if (const CmpInst *CI = dyn_cast<CmpInst>(I1))
return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate();
if (const CallInst *CI = dyn_cast<CallInst>(I1))
return CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
CI->getAttributes() == cast<CallInst>(I2)->getAttributes();
if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1))
return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() &&
CI->getAttributes() == cast<InvokeInst>(I2)->getAttributes();
if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1))
return IVI->getIndices() == cast<InsertValueInst>(I2)->getIndices();
if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1))
return EVI->getIndices() == cast<ExtractValueInst>(I2)->getIndices();
if (const FenceInst *FI = dyn_cast<FenceInst>(I1))
return FI->getOrdering() == cast<FenceInst>(I2)->getOrdering() &&
FI->getSynchScope() == cast<FenceInst>(I2)->getSynchScope();
if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(I1))
return CXI->isVolatile() == cast<AtomicCmpXchgInst>(I2)->isVolatile() &&
CXI->getSuccessOrdering() ==
cast<AtomicCmpXchgInst>(I2)->getSuccessOrdering() &&
CXI->getFailureOrdering() ==
cast<AtomicCmpXchgInst>(I2)->getFailureOrdering() &&
CXI->getSynchScope() == cast<AtomicCmpXchgInst>(I2)->getSynchScope();
if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I1))
return RMWI->getOperation() == cast<AtomicRMWInst>(I2)->getOperation() &&
RMWI->isVolatile() == cast<AtomicRMWInst>(I2)->isVolatile() &&
RMWI->getOrdering() == cast<AtomicRMWInst>(I2)->getOrdering() &&
RMWI->getSynchScope() == cast<AtomicRMWInst>(I2)->getSynchScope();
return true;
}
// Determine whether two GEP operations perform the same underlying arithmetic.
bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1,
const GEPOperator *GEP2) {
unsigned AS = GEP1->getPointerAddressSpace();
if (AS != GEP2->getPointerAddressSpace())
return false;
if (DL) {
// When we have target data, we can reduce the GEP down to the value in bytes
// added to the address.
unsigned BitWidth = DL ? DL->getPointerSizeInBits(AS) : 1;
APInt Offset1(BitWidth, 0), Offset2(BitWidth, 0);
if (GEP1->accumulateConstantOffset(*DL, Offset1) &&
GEP2->accumulateConstantOffset(*DL, Offset2)) {
return Offset1 == Offset2;
}
}
if (GEP1->getPointerOperand()->getType() !=
GEP2->getPointerOperand()->getType())
return false;
if (GEP1->getNumOperands() != GEP2->getNumOperands())
return false;
for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) {
if (!enumerate(GEP1->getOperand(i), GEP2->getOperand(i)))
return false;
}
return true;
}
/// Compare two values used by the two functions under pair-wise comparison. If
/// this is the first time the values are seen, they're added to the mapping so
/// that we will detect mismatches on next use.
/// See comments in declaration for more details.
int FunctionComparator::cmpValues(const Value *L, const Value *R) {
// Catch self-reference case.
if (L == F1) {
if (R == F2)
return 0;
return -1;
}
if (R == F2) {
if (L == F1)
return 0;
return 1;
}
const Constant *ConstL = dyn_cast<Constant>(L);
const Constant *ConstR = dyn_cast<Constant>(R);
if (ConstL && ConstR) {
if (L == R)
return 0;
return cmpConstants(ConstL, ConstR);
}
if (ConstL)
return 1;
if (ConstR)
return -1;
const InlineAsm *InlineAsmL = dyn_cast<InlineAsm>(L);
const InlineAsm *InlineAsmR = dyn_cast<InlineAsm>(R);
if (InlineAsmL && InlineAsmR)
return cmpNumbers((uint64_t)L, (uint64_t)R);
if (InlineAsmL)
return 1;
if (InlineAsmR)
return -1;
auto LeftSN = sn_mapL.insert(std::make_pair(L, sn_mapL.size())),
RightSN = sn_mapR.insert(std::make_pair(R, sn_mapR.size()));
return cmpNumbers(LeftSN.first->second, RightSN.first->second);
}
// Test whether two basic blocks have equivalent behaviour.
bool FunctionComparator::compare(const BasicBlock *BB1, const BasicBlock *BB2) {
BasicBlock::const_iterator F1I = BB1->begin(), F1E = BB1->end();
BasicBlock::const_iterator F2I = BB2->begin(), F2E = BB2->end();
do {
if (!enumerate(F1I, F2I))
return false;
if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) {
const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I);
if (!GEP2)
return false;
if (!enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
2010-05-13 14:45:13 +08:00
return false;
if (!isEquivalentGEP(GEP1, GEP2))
2010-05-13 14:45:13 +08:00
return false;
} else {
if (!isEquivalentOperation(F1I, F2I))
return false;
assert(F1I->getNumOperands() == F2I->getNumOperands());
for (unsigned i = 0, e = F1I->getNumOperands(); i != e; ++i) {
Value *OpF1 = F1I->getOperand(i);
Value *OpF2 = F2I->getOperand(i);
if (!enumerate(OpF1, OpF2))
2010-05-13 14:45:13 +08:00
return false;
if (OpF1->getValueID() != OpF2->getValueID() ||
!isEquivalentType(OpF1->getType(), OpF2->getType()))
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.
sn_mapL.clear();
sn_mapR.clear();
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)))
2010-05-13 14:45:13 +08:00
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) override;
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;
/// DataLayout for more accurate GEP comparisons. May be NULL.
const DataLayout *DL;
/// 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;
DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
DL = DLP ? &DLP->getDataLayout() : nullptr;
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, DL);
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, DL);
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.getDataLayout() == ComparableFunction::LookupOnly ||
RHS.getDataLayout() == ComparableFunction::LookupOnly)
return false;
assert(LHS.getDataLayout() == RHS.getDataLayout() &&
"Comparing functions for different targets");
return FunctionComparator(LHS.getDataLayout(), 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());
[C++11] Add range based accessors for the Use-Def chain of a Value. This requires a number of steps. 1) Move value_use_iterator into the Value class as an implementation detail 2) Change it to actually be a *Use* iterator rather than a *User* iterator. 3) Add an adaptor which is a User iterator that always looks through the Use to the User. 4) Wrap these in Value::use_iterator and Value::user_iterator typedefs. 5) Add the range adaptors as Value::uses() and Value::users(). 6) Update *all* of the callers to correctly distinguish between whether they wanted a use_iterator (and to explicitly dig out the User when needed), or a user_iterator which makes the Use itself totally opaque. Because #6 requires churning essentially everything that walked the Use-Def chains, I went ahead and added all of the range adaptors and switched them to range-based loops where appropriate. Also because the renaming requires at least churning every line of code, it didn't make any sense to split these up into multiple commits -- all of which would touch all of the same lies of code. The result is still not quite optimal. The Value::use_iterator is a nice regular iterator, but Value::user_iterator is an iterator over User*s rather than over the User objects themselves. As a consequence, it fits a bit awkwardly into the range-based world and it has the weird extra-dereferencing 'operator->' that so many of our iterators have. I think this could be fixed by providing something which transforms a range of T&s into a range of T*s, but that *can* be separated into another patch, and it isn't yet 100% clear whether this is the right move. However, this change gets us most of the benefit and cleans up a substantial amount of code around Use and User. =] llvm-svn: 203364
2014-03-09 11:16:01 +08:00
for (auto UI = Old->use_begin(), UE = Old->use_end(); UI != UE;) {
Use *U = &*UI;
++UI;
[C++11] Add range based accessors for the Use-Def chain of a Value. This requires a number of steps. 1) Move value_use_iterator into the Value class as an implementation detail 2) Change it to actually be a *Use* iterator rather than a *User* iterator. 3) Add an adaptor which is a User iterator that always looks through the Use to the User. 4) Wrap these in Value::use_iterator and Value::user_iterator typedefs. 5) Add the range adaptors as Value::uses() and Value::users(). 6) Update *all* of the callers to correctly distinguish between whether they wanted a use_iterator (and to explicitly dig out the User when needed), or a user_iterator which makes the Use itself totally opaque. Because #6 requires churning essentially everything that walked the Use-Def chains, I went ahead and added all of the range adaptors and switched them to range-based loops where appropriate. Also because the renaming requires at least churning every line of code, it didn't make any sense to split these up into multiple commits -- all of which would touch all of the same lies of code. The result is still not quite optimal. The Value::use_iterator is a nice regular iterator, but Value::user_iterator is an iterator over User*s rather than over the User objects themselves. As a consequence, it fits a bit awkwardly into the range-based world and it has the weird extra-dereferencing 'operator->' that so many of our iterators have. I think this could be fixed by providing something which transforms a range of T&s into a range of T*s, but that *can* be separated into another patch, and it isn't yet 100% clear whether this is the right move. However, this change gets us most of the benefit and cleans up a substantial amount of code around Use and User. =] llvm-svn: 203364
2014-03-09 11:16:01 +08:00
CallSite CS(U->getUser());
if (CS && CS.isCallee(U)) {
remove(CS.getInstruction()->getParent()->getParent());
[C++11] Add range based accessors for the Use-Def chain of a Value. This requires a number of steps. 1) Move value_use_iterator into the Value class as an implementation detail 2) Change it to actually be a *Use* iterator rather than a *User* iterator. 3) Add an adaptor which is a User iterator that always looks through the Use to the User. 4) Wrap these in Value::use_iterator and Value::user_iterator typedefs. 5) Add the range adaptors as Value::uses() and Value::users(). 6) Update *all* of the callers to correctly distinguish between whether they wanted a use_iterator (and to explicitly dig out the User when needed), or a user_iterator which makes the Use itself totally opaque. Because #6 requires churning essentially everything that walked the Use-Def chains, I went ahead and added all of the range adaptors and switched them to range-based loops where appropriate. Also because the renaming requires at least churning every line of code, it didn't make any sense to split these up into multiple commits -- all of which would touch all of the same lies of code. The result is still not quite optimal. The Value::use_iterator is a nice regular iterator, but Value::user_iterator is an iterator over User*s rather than over the User objects themselves. As a consequence, it fits a bit awkwardly into the range-based world and it has the weird extra-dereferencing 'operator->' that so many of our iterators have. I think this could be fixed by providing something which transforms a range of T&s into a range of T*s, but that *can* be separated into another patch, and it isn't yet 100% clear whether this is the right move. However, this change gets us most of the benefit and cleans up a substantial amount of code around Use and User. =] llvm-svn: 203364
2014-03-09 11:16:01 +08:00
U->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);
}
// Helper for writeThunk,
// Selects proper bitcast operation,
// but a bit simpler then CastInst::getCastOpcode.
static Value *createCast(IRBuilder<false> &Builder, Value *V, Type *DestTy) {
Type *SrcTy = V->getType();
if (SrcTy->isStructTy()) {
assert(DestTy->isStructTy());
assert(SrcTy->getStructNumElements() == DestTy->getStructNumElements());
Value *Result = UndefValue::get(DestTy);
for (unsigned int I = 0, E = SrcTy->getStructNumElements(); I < E; ++I) {
Value *Element = createCast(
Builder, Builder.CreateExtractValue(V, ArrayRef<unsigned int>(I)),
DestTy->getStructElementType(I));
Result =
Builder.CreateInsertValue(Result, Element, ArrayRef<unsigned int>(I));
}
return Result;
}
assert(!DestTy->isStructTy());
if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
return Builder.CreateIntToPtr(V, DestTy);
else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
return Builder.CreatePtrToInt(V, DestTy);
else
return Builder.CreateBitCast(V, DestTy);
}
// 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(createCast(Builder, (Value*)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(createCast(Builder, 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;
// Don't merge tiny functions, since it can just end up making the function
// larger.
// FIXME: Should still merge them if they are unnamed_addr and produce an
// alias.
if (NewF.getFunc()->size() == 1) {
if (NewF.getFunc()->front().size() <= 2) {
DEBUG(dbgs() << NewF.getFunc()->getName()
<< " is to small to bother merging\n");
return false;
}
}
// 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();
[C++11] Add range based accessors for the Use-Def chain of a Value. This requires a number of steps. 1) Move value_use_iterator into the Value class as an implementation detail 2) Change it to actually be a *Use* iterator rather than a *User* iterator. 3) Add an adaptor which is a User iterator that always looks through the Use to the User. 4) Wrap these in Value::use_iterator and Value::user_iterator typedefs. 5) Add the range adaptors as Value::uses() and Value::users(). 6) Update *all* of the callers to correctly distinguish between whether they wanted a use_iterator (and to explicitly dig out the User when needed), or a user_iterator which makes the Use itself totally opaque. Because #6 requires churning essentially everything that walked the Use-Def chains, I went ahead and added all of the range adaptors and switched them to range-based loops where appropriate. Also because the renaming requires at least churning every line of code, it didn't make any sense to split these up into multiple commits -- all of which would touch all of the same lies of code. The result is still not quite optimal. The Value::use_iterator is a nice regular iterator, but Value::user_iterator is an iterator over User*s rather than over the User objects themselves. As a consequence, it fits a bit awkwardly into the range-based world and it has the weird extra-dereferencing 'operator->' that so many of our iterators have. I think this could be fixed by providing something which transforms a range of T&s into a range of T*s, but that *can* be separated into another patch, and it isn't yet 100% clear whether this is the right move. However, this change gets us most of the benefit and cleans up a substantial amount of code around Use and User. =] llvm-svn: 203364
2014-03-09 11:16:01 +08:00
for (User *U : V->users()) {
if (Instruction *I = dyn_cast<Instruction>(U)) {
remove(I->getParent()->getParent());
[C++11] Add range based accessors for the Use-Def chain of a Value. This requires a number of steps. 1) Move value_use_iterator into the Value class as an implementation detail 2) Change it to actually be a *Use* iterator rather than a *User* iterator. 3) Add an adaptor which is a User iterator that always looks through the Use to the User. 4) Wrap these in Value::use_iterator and Value::user_iterator typedefs. 5) Add the range adaptors as Value::uses() and Value::users(). 6) Update *all* of the callers to correctly distinguish between whether they wanted a use_iterator (and to explicitly dig out the User when needed), or a user_iterator which makes the Use itself totally opaque. Because #6 requires churning essentially everything that walked the Use-Def chains, I went ahead and added all of the range adaptors and switched them to range-based loops where appropriate. Also because the renaming requires at least churning every line of code, it didn't make any sense to split these up into multiple commits -- all of which would touch all of the same lies of code. The result is still not quite optimal. The Value::use_iterator is a nice regular iterator, but Value::user_iterator is an iterator over User*s rather than over the User objects themselves. As a consequence, it fits a bit awkwardly into the range-based world and it has the weird extra-dereferencing 'operator->' that so many of our iterators have. I think this could be fixed by providing something which transforms a range of T&s into a range of T*s, but that *can* be separated into another patch, and it isn't yet 100% clear whether this is the right move. However, this change gets us most of the benefit and cleans up a substantial amount of code around Use and User. =] llvm-svn: 203364
2014-03-09 11:16:01 +08:00
} else if (isa<GlobalValue>(U)) {
// do nothing
[C++11] Add range based accessors for the Use-Def chain of a Value. This requires a number of steps. 1) Move value_use_iterator into the Value class as an implementation detail 2) Change it to actually be a *Use* iterator rather than a *User* iterator. 3) Add an adaptor which is a User iterator that always looks through the Use to the User. 4) Wrap these in Value::use_iterator and Value::user_iterator typedefs. 5) Add the range adaptors as Value::uses() and Value::users(). 6) Update *all* of the callers to correctly distinguish between whether they wanted a use_iterator (and to explicitly dig out the User when needed), or a user_iterator which makes the Use itself totally opaque. Because #6 requires churning essentially everything that walked the Use-Def chains, I went ahead and added all of the range adaptors and switched them to range-based loops where appropriate. Also because the renaming requires at least churning every line of code, it didn't make any sense to split these up into multiple commits -- all of which would touch all of the same lies of code. The result is still not quite optimal. The Value::use_iterator is a nice regular iterator, but Value::user_iterator is an iterator over User*s rather than over the User objects themselves. As a consequence, it fits a bit awkwardly into the range-based world and it has the weird extra-dereferencing 'operator->' that so many of our iterators have. I think this could be fixed by providing something which transforms a range of T&s into a range of T*s, but that *can* be separated into another patch, and it isn't yet 100% clear whether this is the right move. However, this change gets us most of the benefit and cleans up a substantial amount of code around Use and User. =] llvm-svn: 203364
2014-03-09 11:16:01 +08:00
} else if (Constant *C = dyn_cast<Constant>(U)) {
for (User *UU : C->users())
Worklist.push_back(UU);
}
}
}
}