// -- We define Function* container class with custom "operator<" (FunctionPtr).
// -- "FunctionPtr" instances are stored in std::set collection, so every
// std::set::insert operation will give you result in log(N) time.
+//
+// As an optimization, a hash of the function structure is calculated first, and
+// two functions are only compared if they have the same hash. This hash is
+// cheap to compute, and has the property that if function F == G according to
+// the comparison function, then hash(F) == hash(G). This consistency property
+// is critical to ensuring all possible merging opportunities are exploited.
+// Collisions in the hash affect the speed of the pass but not the correctness
+// or determinism of the resulting transformation.
//
// When a match is found the functions are folded. If both functions are
// overridable, we move the functionality into a new internal function and
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/Hashing.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/ValueHandle.h"
+#include "llvm/IR/ValueMap.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.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"
namespace {
+/// GlobalNumberState assigns an integer to each global value in the program,
+/// which is used by the comparison routine to order references to globals. This
+/// state must be preserved throughout the pass, because Functions and other
+/// globals need to maintain their relative order. Globals are assigned a number
+/// when they are first visited. This order is deterministic, and so the
+/// assigned numbers are as well. When two functions are merged, neither number
+/// is updated. If the symbols are weak, this would be incorrect. If they are
+/// strong, then one will be replaced at all references to the other, and so
+/// direct callsites will now see one or the other symbol, and no update is
+/// necessary. Note that if we were guaranteed unique names, we could just
+/// compare those, but this would not work for stripped bitcodes or for those
+/// few symbols without a name.
+class GlobalNumberState {
+ struct Config : ValueMapConfig<GlobalValue*> {
+ enum { FollowRAUW = false };
+ };
+ // Each GlobalValue is mapped to an identifier. The Config ensures when RAUW
+ // occurs, the mapping does not change. Tracking changes is unnecessary, and
+ // also problematic for weak symbols (which may be overwritten).
+ typedef ValueMap<GlobalValue *, uint64_t, Config> ValueNumberMap;
+ ValueNumberMap GlobalNumbers;
+ // The next unused serial number to assign to a global.
+ uint64_t NextNumber;
+ public:
+ GlobalNumberState() : GlobalNumbers(), NextNumber(0) {}
+ uint64_t getNumber(GlobalValue* Global) {
+ ValueNumberMap::iterator MapIter;
+ bool Inserted;
+ std::tie(MapIter, Inserted) = GlobalNumbers.insert({Global, NextNumber});
+ if (Inserted)
+ NextNumber++;
+ return MapIter->second;
+ }
+ void clear() {
+ GlobalNumbers.clear();
+ }
+};
+
/// 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 Function *F1, const Function *F2)
- : FnL(F1), FnR(F2) {}
+ FunctionComparator(const Function *F1, const Function *F2,
+ GlobalNumberState* GN)
+ : FnL(F1), FnR(F2), GlobalNumbers(GN) {}
/// Test whether the two functions have equivalent behaviour.
int compare();
+ /// Hash a function. Equivalent functions will have the same hash, and unequal
+ /// functions will have different hashes with high probability.
+ typedef uint64_t FunctionHash;
+ static FunctionHash functionHash(Function &);
private:
/// Test whether two basic blocks have equivalent behaviour.
- int compare(const BasicBlock *BBL, const BasicBlock *BBR);
+ int cmpBasicBlocks(const BasicBlock *BBL, const BasicBlock *BBR);
/// Constants comparison.
/// Its analog to lexicographical comparison between hypothetical numbers
/// If these properties are equal - compare their contents.
int cmpConstants(const Constant *L, const Constant *R);
+ /// Compares two global values by number. Uses the GlobalNumbersState to
+ /// identify the same gobals across function calls.
+ int cmpGlobalValues(GlobalValue *L, GlobalValue *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.
///
/// 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:
+ /// 2. If types are integers, check that they have the same width. If they
+ /// are vectors, check that they have the same count and subtype.
+ /// 3. Types have the same ID, so check whether they are one of:
/// * Void
/// * Float
/// * Double
/// * PPC_FP128
/// * Label
/// * Metadata
- /// If so - return 0, yes - we can treat these types as equal only because
- /// their IDs are same.
+ /// We can treat these types as equal whenever 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.
int cmpTypes(Type *TyL, Type *TyR) const;
int cmpNumbers(uint64_t L, uint64_t R) const;
-
int cmpAPInts(const APInt &L, const APInt &R) const;
int cmpAPFloats(const APFloat &L, const APFloat &R) const;
- int cmpStrings(StringRef L, StringRef R) const;
+ int cmpInlineAsm(const InlineAsm *L, const InlineAsm *R) const;
+ int cmpMem(StringRef L, StringRef R) const;
int cmpAttrs(const AttributeSet L, const AttributeSet R) const;
+ int cmpRangeMetadata(const MDNode* L, const MDNode* R) const;
// The two functions undergoing comparison.
const Function *FnL, *FnR;
/// 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;
+
+ // The global state we will use
+ GlobalNumberState* GlobalNumbers;
};
class FunctionNode {
mutable AssertingVH<Function> F;
-
+ FunctionComparator::FunctionHash Hash;
public:
- FunctionNode(Function *F) : F(F) {}
+ // Note the hash is recalculated potentially multiple times, but it is cheap.
+ FunctionNode(Function *F)
+ : F(F), Hash(FunctionComparator::functionHash(*F)) {}
Function *getFunc() const { return F; }
+ FunctionComparator::FunctionHash getHash() const { return Hash; }
/// Replace the reference to the function F by the function G, assuming their
/// implementations are equal.
void replaceBy(Function *G) const {
- assert(!(*this < FunctionNode(G)) && !(FunctionNode(G) < *this) &&
- "The two functions must be equal");
-
F = G;
}
- void release() { F = 0; }
- bool operator<(const FunctionNode &RHS) const {
- return (FunctionComparator(F, RHS.getFunc()).compare()) == -1;
- }
+ void release() { F = nullptr; }
};
-}
+} // end anonymous namespace
int FunctionComparator::cmpNumbers(uint64_t L, uint64_t R) const {
if (L < R) return -1;
}
int FunctionComparator::cmpAPFloats(const APFloat &L, const APFloat &R) const {
- if (int Res = cmpNumbers((uint64_t)&L.getSemantics(),
- (uint64_t)&R.getSemantics()))
+ // Floats are ordered first by semantics (i.e. float, double, half, etc.),
+ // then by value interpreted as a bitstring (aka APInt).
+ const fltSemantics &SL = L.getSemantics(), &SR = R.getSemantics();
+ if (int Res = cmpNumbers(APFloat::semanticsPrecision(SL),
+ APFloat::semanticsPrecision(SR)))
+ return Res;
+ if (int Res = cmpNumbers(APFloat::semanticsMaxExponent(SL),
+ APFloat::semanticsMaxExponent(SR)))
+ return Res;
+ if (int Res = cmpNumbers(APFloat::semanticsMinExponent(SL),
+ APFloat::semanticsMinExponent(SR)))
+ return Res;
+ if (int Res = cmpNumbers(APFloat::semanticsSizeInBits(SL),
+ APFloat::semanticsSizeInBits(SR)))
return Res;
return cmpAPInts(L.bitcastToAPInt(), R.bitcastToAPInt());
}
-int FunctionComparator::cmpStrings(StringRef L, StringRef R) const {
+int FunctionComparator::cmpMem(StringRef L, StringRef R) const {
// Prevent heavy comparison, compare sizes first.
if (int Res = cmpNumbers(L.size(), R.size()))
return Res;
return 0;
}
+int FunctionComparator::cmpRangeMetadata(const MDNode* L,
+ const MDNode* R) const {
+ if (L == R)
+ return 0;
+ if (!L)
+ return -1;
+ if (!R)
+ return 1;
+ // Range metadata is a sequence of numbers. Make sure they are the same
+ // sequence.
+ // TODO: Note that as this is metadata, it is possible to drop and/or merge
+ // this data when considering functions to merge. Thus this comparison would
+ // return 0 (i.e. equivalent), but merging would become more complicated
+ // because the ranges would need to be unioned. It is not likely that
+ // functions differ ONLY in this metadata if they are actually the same
+ // function semantically.
+ if (int Res = cmpNumbers(L->getNumOperands(), R->getNumOperands()))
+ return Res;
+ for (size_t I = 0; I < L->getNumOperands(); ++I) {
+ ConstantInt* LLow = mdconst::extract<ConstantInt>(L->getOperand(I));
+ ConstantInt* RLow = mdconst::extract<ConstantInt>(R->getOperand(I));
+ if (int Res = cmpAPInts(LLow->getValue(), RLow->getValue()))
+ return Res;
+ }
+ return 0;
+}
+
/// Constants comparison:
/// 1. Check whether type of L constant could be losslessly bitcasted to R
/// type.
unsigned TyLWidth = 0;
unsigned TyRWidth = 0;
- if (const VectorType *VecTyL = dyn_cast<VectorType>(TyL))
+ if (auto *VecTyL = dyn_cast<VectorType>(TyL))
TyLWidth = VecTyL->getBitWidth();
- if (const VectorType *VecTyR = dyn_cast<VectorType>(TyR))
+ if (auto *VecTyR = dyn_cast<VectorType>(TyR))
TyRWidth = VecTyR->getBitWidth();
if (TyLWidth != TyRWidth)
if (!L->isNullValue() && R->isNullValue())
return -1;
+ auto GlobalValueL = const_cast<GlobalValue*>(dyn_cast<GlobalValue>(L));
+ auto GlobalValueR = const_cast<GlobalValue*>(dyn_cast<GlobalValue>(R));
+ if (GlobalValueL && GlobalValueR) {
+ return cmpGlobalValues(GlobalValueL, GlobalValueR);
+ }
+
if (int Res = cmpNumbers(L->getValueID(), R->getValueID()))
return Res;
+ if (const auto *SeqL = dyn_cast<ConstantDataSequential>(L)) {
+ const auto *SeqR = cast<ConstantDataSequential>(R);
+ // This handles ConstantDataArray and ConstantDataVector. Note that we
+ // compare the two raw data arrays, which might differ depending on the host
+ // endianness. This isn't a problem though, because the endiness of a module
+ // will affect the order of the constants, but this order is the same
+ // for a given input module and host platform.
+ return cmpMem(SeqL->getRawDataValues(), SeqR->getRawDataValues());
+ }
+
switch (L->getValueID()) {
- case Value::UndefValueVal: return TypesRes;
+ case Value::UndefValueVal:
+ case Value::ConstantTokenNoneVal:
+ return TypesRes;
case Value::ConstantIntVal: {
const APInt &LInt = cast<ConstantInt>(L)->getValue();
const APInt &RInt = cast<ConstantInt>(R)->getValue();
}
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);
+ case Value::BlockAddressVal: {
+ const BlockAddress *LBA = cast<BlockAddress>(L);
+ const BlockAddress *RBA = cast<BlockAddress>(R);
+ if (int Res = cmpValues(LBA->getFunction(), RBA->getFunction()))
+ return Res;
+ if (LBA->getFunction() == RBA->getFunction()) {
+ // They are BBs in the same function. Order by which comes first in the
+ // BB order of the function. This order is deterministic.
+ Function* F = LBA->getFunction();
+ BasicBlock *LBB = LBA->getBasicBlock();
+ BasicBlock *RBB = RBA->getBasicBlock();
+ if (LBB == RBB)
+ return 0;
+ for(BasicBlock &BB : F->getBasicBlockList()) {
+ if (&BB == LBB) {
+ assert(&BB != RBB);
+ return -1;
+ }
+ if (&BB == RBB)
+ return 1;
+ }
+ llvm_unreachable("Basic Block Address does not point to a basic block in "
+ "its function.");
+ return -1;
+ } else {
+ // cmpValues said the functions are the same. So because they aren't
+ // literally the same pointer, they must respectively be the left and
+ // right functions.
+ assert(LBA->getFunction() == FnL && RBA->getFunction() == FnR);
+ // cmpValues will tell us if these are equivalent BasicBlocks, in the
+ // context of their respective functions.
+ return cmpValues(LBA->getBasicBlock(), RBA->getBasicBlock());
+ }
+ }
+ default: // Unknown constant, abort.
+ DEBUG(dbgs() << "Looking at valueID " << L->getValueID() << "\n");
+ llvm_unreachable("Constant ValueID not recognized.");
+ return -1;
}
}
+int FunctionComparator::cmpGlobalValues(GlobalValue *L, GlobalValue* R) {
+ return cmpNumbers(GlobalNumbers->getNumber(L), GlobalNumbers->getNumber(R));
+}
+
/// cmpType - compares two types,
/// defines total ordering among the types set.
/// See method declaration comments for more details.
int FunctionComparator::cmpTypes(Type *TyL, Type *TyR) const {
-
PointerType *PTyL = dyn_cast<PointerType>(TyL);
PointerType *PTyR = dyn_cast<PointerType>(TyR);
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);
-
+ return cmpNumbers(cast<IntegerType>(TyL)->getBitWidth(),
+ cast<IntegerType>(TyR)->getBitWidth());
+ case Type::VectorTyID: {
+ VectorType *VTyL = cast<VectorType>(TyL), *VTyR = cast<VectorType>(TyR);
+ if (int Res = cmpNumbers(VTyL->getNumElements(), VTyR->getNumElements()))
+ return Res;
+ return cmpTypes(VTyL->getElementType(), VTyR->getElementType());
+ }
+ // TyL == TyR would have returned true earlier, because types are uniqued.
case Type::VoidTyID:
case Type::FloatTyID:
case Type::DoubleTyID:
case Type::PPC_FP128TyID:
case Type::LabelTyID:
case Type::MetadataTyID:
+ case Type::TokenTyID:
return 0;
case Type::PointerTyID: {
if (int Res =
cmpNumbers(LI->getSynchScope(), cast<LoadInst>(R)->getSynchScope()))
return Res;
- return cmpNumbers((uint64_t)LI->getMetadata(LLVMContext::MD_range),
- (uint64_t)cast<LoadInst>(R)->getMetadata(LLVMContext::MD_range));
+ return cmpRangeMetadata(LI->getMetadata(LLVMContext::MD_range),
+ cast<LoadInst>(R)->getMetadata(LLVMContext::MD_range));
}
if (const StoreInst *SI = dyn_cast<StoreInst>(L)) {
if (int Res =
if (int Res =
cmpAttrs(CI->getAttributes(), cast<CallInst>(R)->getAttributes()))
return Res;
- return cmpNumbers(
- (uint64_t)CI->getMetadata(LLVMContext::MD_range),
- (uint64_t)cast<CallInst>(R)->getMetadata(LLVMContext::MD_range));
+ return cmpRangeMetadata(
+ CI->getMetadata(LLVMContext::MD_range),
+ cast<CallInst>(R)->getMetadata(LLVMContext::MD_range));
}
if (const InvokeInst *CI = dyn_cast<InvokeInst>(L)) {
if (int Res = cmpNumbers(CI->getCallingConv(),
if (int Res =
cmpAttrs(CI->getAttributes(), cast<InvokeInst>(R)->getAttributes()))
return Res;
- return cmpNumbers(
- (uint64_t)CI->getMetadata(LLVMContext::MD_range),
- (uint64_t)cast<InvokeInst>(R)->getMetadata(LLVMContext::MD_range));
+ return cmpRangeMetadata(
+ CI->getMetadata(LLVMContext::MD_range),
+ cast<InvokeInst>(R)->getMetadata(LLVMContext::MD_range));
}
if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(L)) {
ArrayRef<unsigned> LIndices = IVI->getIndices();
if (GEPL->accumulateConstantOffset(DL, OffsetL) &&
GEPR->accumulateConstantOffset(DL, OffsetR))
return cmpAPInts(OffsetL, OffsetR);
-
- if (int Res = cmpNumbers((uint64_t)GEPL->getPointerOperand()->getType(),
- (uint64_t)GEPR->getPointerOperand()->getType()))
+ if (int Res = cmpTypes(GEPL->getSourceElementType(),
+ GEPR->getSourceElementType()))
return Res;
if (int Res = cmpNumbers(GEPL->getNumOperands(), GEPR->getNumOperands()))
return 0;
}
+int FunctionComparator::cmpInlineAsm(const InlineAsm *L,
+ const InlineAsm *R) const {
+ // InlineAsm's are uniqued. If they are the same pointer, obviously they are
+ // the same, otherwise compare the fields.
+ if (L == R)
+ return 0;
+ if (int Res = cmpTypes(L->getFunctionType(), R->getFunctionType()))
+ return Res;
+ if (int Res = cmpMem(L->getAsmString(), R->getAsmString()))
+ return Res;
+ if (int Res = cmpMem(L->getConstraintString(), R->getConstraintString()))
+ return Res;
+ if (int Res = cmpNumbers(L->hasSideEffects(), R->hasSideEffects()))
+ return Res;
+ if (int Res = cmpNumbers(L->isAlignStack(), R->isAlignStack()))
+ return Res;
+ if (int Res = cmpNumbers(L->getDialect(), R->getDialect()))
+ return Res;
+ llvm_unreachable("InlineAsm blocks were not uniqued.");
+ return 0;
+}
+
/// 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.
const InlineAsm *InlineAsmR = dyn_cast<InlineAsm>(R);
if (InlineAsmL && InlineAsmR)
- return cmpNumbers((uint64_t)L, (uint64_t)R);
+ return cmpInlineAsm(InlineAsmL, InlineAsmR);
if (InlineAsmL)
return 1;
if (InlineAsmR)
return cmpNumbers(LeftSN.first->second, RightSN.first->second);
}
// Test whether two basic blocks have equivalent behaviour.
-int FunctionComparator::compare(const BasicBlock *BBL, const BasicBlock *BBR) {
+int FunctionComparator::cmpBasicBlocks(const BasicBlock *BBL,
+ const BasicBlock *BBR) {
BasicBlock::const_iterator InstL = BBL->begin(), InstLE = BBL->end();
BasicBlock::const_iterator InstR = BBR->begin(), InstRE = BBR->end();
do {
- if (int Res = cmpValues(InstL, InstR))
+ if (int Res = cmpValues(&*InstL, &*InstR))
return Res;
const GetElementPtrInst *GEPL = dyn_cast<GetElementPtrInst>(InstL);
if (int Res = cmpGEPs(GEPL, GEPR))
return Res;
} else {
- if (int Res = cmpOperations(InstL, InstR))
+ if (int Res = cmpOperations(&*InstL, &*InstR))
return Res;
assert(InstL->getNumOperands() == InstR->getNumOperands());
Value *OpR = InstR->getOperand(i);
if (int Res = cmpValues(OpL, OpR))
return Res;
- if (int Res = cmpNumbers(OpL->getValueID(), OpR->getValueID()))
- return Res;
- // TODO: Already checked in cmpOperation
- if (int Res = cmpTypes(OpL->getType(), OpR->getType()))
- return Res;
+ // cmpValues should ensure this is true.
+ assert(cmpTypes(OpL->getType(), OpR->getType()) == 0);
}
}
// Test whether the two functions have equivalent behaviour.
int FunctionComparator::compare() {
-
sn_mapL.clear();
sn_mapR.clear();
return Res;
if (FnL->hasGC()) {
- if (int Res = cmpNumbers((uint64_t)FnL->getGC(), (uint64_t)FnR->getGC()))
+ if (int Res = cmpMem(FnL->getGC(), FnR->getGC()))
return Res;
}
return Res;
if (FnL->hasSection()) {
- if (int Res = cmpStrings(FnL->getSection(), FnR->getSection()))
+ if (int Res = cmpMem(FnL->getSection(), FnR->getSection()))
return Res;
}
ArgRI = FnR->arg_begin(),
ArgLE = FnL->arg_end();
ArgLI != ArgLE; ++ArgLI, ++ArgRI) {
- if (cmpValues(ArgLI, ArgRI) != 0)
+ if (cmpValues(&*ArgLI, &*ArgRI) != 0)
llvm_unreachable("Arguments repeat!");
}
if (int Res = cmpValues(BBL, BBR))
return Res;
- if (int Res = compare(BBL, BBR))
+ if (int Res = cmpBasicBlocks(BBL, BBR))
return Res;
const TerminatorInst *TermL = BBL->getTerminator();
return 0;
}
+// Accumulate the hash of a sequence of 64-bit integers. This is similar to a
+// hash of a sequence of 64bit ints, but the entire input does not need to be
+// available at once. This interface is necessary for functionHash because it
+// needs to accumulate the hash as the structure of the function is traversed
+// without saving these values to an intermediate buffer. This form of hashing
+// is not often needed, as usually the object to hash is just read from a
+// buffer.
+class HashAccumulator64 {
+ uint64_t Hash;
+public:
+ // Initialize to random constant, so the state isn't zero.
+ HashAccumulator64() { Hash = 0x6acaa36bef8325c5ULL; }
+ void add(uint64_t V) {
+ Hash = llvm::hashing::detail::hash_16_bytes(Hash, V);
+ }
+ // No finishing is required, because the entire hash value is used.
+ uint64_t getHash() { return Hash; }
+};
+
+// A function hash is calculated by considering only the number of arguments and
+// whether a function is varargs, the order of basic blocks (given by the
+// successors of each basic block in depth first order), and the order of
+// opcodes of each instruction within each of these basic blocks. This mirrors
+// the strategy compare() uses to compare functions by walking the BBs in depth
+// first order and comparing each instruction in sequence. Because this hash
+// does not look at the operands, it is insensitive to things such as the
+// target of calls and the constants used in the function, which makes it useful
+// when possibly merging functions which are the same modulo constants and call
+// targets.
+FunctionComparator::FunctionHash FunctionComparator::functionHash(Function &F) {
+ HashAccumulator64 H;
+ H.add(F.isVarArg());
+ H.add(F.arg_size());
+
+ SmallVector<const BasicBlock *, 8> BBs;
+ SmallSet<const BasicBlock *, 16> VisitedBBs;
+
+ // Walk the blocks in the same order as FunctionComparator::cmpBasicBlocks(),
+ // accumulating the hash of the function "structure." (BB and opcode sequence)
+ BBs.push_back(&F.getEntryBlock());
+ VisitedBBs.insert(BBs[0]);
+ while (!BBs.empty()) {
+ const BasicBlock *BB = BBs.pop_back_val();
+ // This random value acts as a block header, as otherwise the partition of
+ // opcodes into BBs wouldn't affect the hash, only the order of the opcodes
+ H.add(45798);
+ for (auto &Inst : *BB) {
+ H.add(Inst.getOpcode());
+ }
+ const TerminatorInst *Term = BB->getTerminator();
+ for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
+ if (!VisitedBBs.insert(Term->getSuccessor(i)).second)
+ continue;
+ BBs.push_back(Term->getSuccessor(i));
+ }
+ }
+ return H.getHash();
+}
+
+
namespace {
/// MergeFunctions finds functions which will generate identical machine code,
public:
static char ID;
MergeFunctions()
- : ModulePass(ID), HasGlobalAliases(false) {
+ : ModulePass(ID), FnTree(FunctionNodeCmp(&GlobalNumbers)), FNodesInTree(),
+ HasGlobalAliases(false) {
initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M) override;
private:
- typedef std::set<FunctionNode> FnTreeType;
+ // The function comparison operator is provided here so that FunctionNodes do
+ // not need to become larger with another pointer.
+ class FunctionNodeCmp {
+ GlobalNumberState* GlobalNumbers;
+ public:
+ FunctionNodeCmp(GlobalNumberState* GN) : GlobalNumbers(GN) {}
+ bool operator()(const FunctionNode &LHS, const FunctionNode &RHS) const {
+ // Order first by hashes, then full function comparison.
+ if (LHS.getHash() != RHS.getHash())
+ return LHS.getHash() < RHS.getHash();
+ FunctionComparator FCmp(LHS.getFunc(), RHS.getFunc(), GlobalNumbers);
+ return FCmp.compare() == -1;
+ }
+ };
+ typedef std::set<FunctionNode, FunctionNodeCmp> FnTreeType;
+
+ GlobalNumberState GlobalNumbers;
/// A work queue of functions that may have been modified and should be
/// analyzed again.
void writeAlias(Function *F, Function *G);
/// Replace function F with function G in the function tree.
- void replaceFunctionInTree(FnTreeType::iterator &IterToF, Function *G);
+ void replaceFunctionInTree(const FunctionNode &FN, Function *G);
/// The set of all distinct functions. Use the insert() and remove() methods
- /// to modify it.
+ /// to modify it. The map allows efficient lookup and deferring of Functions.
FnTreeType FnTree;
+ // Map functions to the iterators of the FunctionNode which contains them
+ // in the FnTree. This must be updated carefully whenever the FnTree is
+ // modified, i.e. in insert(), remove(), and replaceFunctionInTree(), to avoid
+ // dangling iterators into FnTree. The invariant that preserves this is that
+ // there is exactly one mapping F -> FN for each FunctionNode FN in FnTree.
+ ValueMap<Function*, FnTreeType::iterator> FNodesInTree;
/// Whether or not the target supports global aliases.
bool HasGlobalAliases;
};
-} // end anonymous namespace
+} // end anonymous namespace
char MergeFunctions::ID = 0;
INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)
for (std::vector<WeakVH>::iterator J = I; J != E && j < Max; ++J, ++j) {
Function *F1 = cast<Function>(*I);
Function *F2 = cast<Function>(*J);
- int Res1 = FunctionComparator(F1, F2).compare();
- int Res2 = FunctionComparator(F2, F1).compare();
+ int Res1 = FunctionComparator(F1, F2, &GlobalNumbers).compare();
+ int Res2 = FunctionComparator(F2, F1, &GlobalNumbers).compare();
// If F1 <= F2, then F2 >= F1, otherwise report failure.
if (Res1 != -Res2) {
continue;
Function *F3 = cast<Function>(*K);
- int Res3 = FunctionComparator(F1, F3).compare();
- int Res4 = FunctionComparator(F2, F3).compare();
+ int Res3 = FunctionComparator(F1, F3, &GlobalNumbers).compare();
+ int Res4 = FunctionComparator(F2, F3, &GlobalNumbers).compare();
bool Transitive = true;
bool MergeFunctions::runOnModule(Module &M) {
bool Changed = false;
- for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
- if (!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
- Deferred.push_back(WeakVH(I));
+ // All functions in the module, ordered by hash. Functions with a unique
+ // hash value are easily eliminated.
+ std::vector<std::pair<FunctionComparator::FunctionHash, Function *>>
+ HashedFuncs;
+ for (Function &Func : M) {
+ if (!Func.isDeclaration() && !Func.hasAvailableExternallyLinkage()) {
+ HashedFuncs.push_back({FunctionComparator::functionHash(Func), &Func});
+ }
}
+ std::stable_sort(
+ HashedFuncs.begin(), HashedFuncs.end(),
+ [](const std::pair<FunctionComparator::FunctionHash, Function *> &a,
+ const std::pair<FunctionComparator::FunctionHash, Function *> &b) {
+ return a.first < b.first;
+ });
+
+ auto S = HashedFuncs.begin();
+ for (auto I = HashedFuncs.begin(), IE = HashedFuncs.end(); I != IE; ++I) {
+ // If the hash value matches the previous value or the next one, we must
+ // consider merging it. Otherwise it is dropped and never considered again.
+ if ((I != S && std::prev(I)->first == I->first) ||
+ (std::next(I) != IE && std::next(I)->first == I->first) ) {
+ Deferred.push_back(WeakVH(I->second));
+ }
+ }
+
do {
std::vector<WeakVH> Worklist;
Deferred.swap(Worklist);
} while (!Deferred.empty());
FnTree.clear();
+ GlobalNumbers.clear();
return Changed;
}
CallSite CS(U->getUser());
if (CS && CS.isCallee(U)) {
// Transfer the called function's attributes to the call site. Due to the
- // bitcast we will 'loose' ABI changing attributes because the 'called
+ // bitcast we will 'lose' ABI changing attributes because the 'called
// function' is no longer a Function* but the bitcast. Code that looks up
// the attributes from the called function will fail.
+
+ // FIXME: This is not actually true, at least not anymore. The callsite
+ // will always have the same ABI affecting attributes as the callee,
+ // because otherwise the original input has UB. Note that Old and New
+ // always have matching ABI, so no attributes need to be changed.
+ // Transferring other attributes may help other optimizations, but that
+ // should be done uniformly and not in this ad-hoc way.
auto &Context = New->getContext();
auto NewFuncAttrs = New->getAttributes();
auto CallSiteAttrs = CS.getAttributes();
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)));
+ for (Argument & AI : NewG->args()) {
+ Args.push_back(createCast(Builder, &AI, FFTy->getParamType(i)));
++i;
}
CallInst *CI = Builder.CreateCall(F, Args);
CI->setTailCall();
CI->setCallingConv(F->getCallingConv());
+ CI->setAttributes(F->getAttributes());
if (NewG->getReturnType()->isVoidTy()) {
Builder.CreateRetVoid();
} else {
// Replace G with an alias to F and delete G.
void MergeFunctions::writeAlias(Function *F, Function *G) {
- PointerType *PTy = G->getType();
- auto *GA = GlobalAlias::create(PTy, G->getLinkage(), "", F);
+ auto *GA = GlobalAlias::create(G->getLinkage(), "", F);
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
GA->takeName(G);
GA->setVisibility(G->getVisibility());
++NumFunctionsMerged;
}
-/// Replace function F for function G in the map.
-void MergeFunctions::replaceFunctionInTree(FnTreeType::iterator &IterToF,
+/// Replace function F by function G.
+void MergeFunctions::replaceFunctionInTree(const FunctionNode &FN,
Function *G) {
- Function *F = IterToF->getFunc();
-
- // A total order is already guaranteed otherwise because we process strong
- // functions before weak functions.
- assert(((F->mayBeOverridden() && G->mayBeOverridden()) ||
- (!F->mayBeOverridden() && !G->mayBeOverridden())) &&
- "Only change functions if both are strong or both are weak");
- (void)F;
-
- IterToF->replaceBy(G);
+ Function *F = FN.getFunc();
+ assert(FunctionComparator(F, G, &GlobalNumbers).compare() == 0 &&
+ "The two functions must be equal");
+
+ auto I = FNodesInTree.find(F);
+ assert(I != FNodesInTree.end() && "F should be in FNodesInTree");
+ assert(FNodesInTree.count(G) == 0 && "FNodesInTree should not contain G");
+
+ FnTreeType::iterator IterToFNInFnTree = I->second;
+ assert(&(*IterToFNInFnTree) == &FN && "F should map to FN in FNodesInTree.");
+ // Remove F -> FN and insert G -> FN
+ FNodesInTree.erase(I);
+ FNodesInTree.insert({G, IterToFNInFnTree});
+ // Replace F with G in FN, which is stored inside the FnTree.
+ FN.replaceBy(G);
}
// Insert a ComparableFunction into the FnTree, or merge it away if equal to one
FnTree.insert(FunctionNode(NewFunction));
if (Result.second) {
+ assert(FNodesInTree.count(NewFunction) == 0);
+ FNodesInTree.insert({NewFunction, Result.first});
DEBUG(dbgs() << "Inserting as unique: " << NewFunction->getName() << '\n');
return false;
}
if (OldF.getFunc()->getName() > NewFunction->getName()) {
// Swap the two functions.
Function *F = OldF.getFunc();
- replaceFunctionInTree(Result.first, NewFunction);
+ replaceFunctionInTree(*Result.first, NewFunction);
NewFunction = F;
assert(OldF.getFunc() != F && "Must have swapped the functions.");
}
// Remove a function from FnTree. If it was already in FnTree, 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.
- FnTreeType::iterator found = FnTree.find(FunctionNode(F));
- size_t Erased = 0;
- if (found != FnTree.end() && found->getFunc() == F) {
- Erased = 1;
- FnTree.erase(found);
- }
-
- if (Erased) {
- DEBUG(dbgs() << "Removed " << F->getName()
- << " from set and deferred it.\n");
+ auto I = FNodesInTree.find(F);
+ if (I != FNodesInTree.end()) {
+ DEBUG(dbgs() << "Deferred " << F->getName()<< ".\n");
+ FnTree.erase(I->second);
+ // I->second has been invalidated, remove it from the FNodesInTree map to
+ // preserve the invariant.
+ FNodesInTree.erase(I);
Deferred.emplace_back(F);
}
}
projects / oota-llvm.git / blobdiff