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-rw-r--r--lib/Transforms/IPO/MergeFunctions.cpp646
1 files changed, 431 insertions, 215 deletions
diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index 5d838f9..cccffca 100644
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -67,42 +67,87 @@
using namespace llvm;
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");
+
+/// 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) {
+ const FunctionType *FTy = F->getFunctionType();
-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) {}
-
- bool runOnModule(Module &M);
-
- private:
- /// MergeTwoFunctions - 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) const;
-
- /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also
- /// replace direct uses of G with bitcast(F).
- void WriteThunk(Function *F, Function *G) const;
-
- TargetData *TD;
- };
+ FoldingSetNodeID ID;
+ ID.AddInteger(F->size());
+ ID.AddInteger(F->getCallingConv());
+ ID.AddBoolean(F->hasGC());
+ ID.AddBoolean(FTy->isVarArg());
+ ID.AddInteger(FTy->getReturnType()->getTypeID());
+ for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
+ ID.AddInteger(FTy->getParamType(i)->getTypeID());
+ return ID.ComputeHash();
}
-char MergeFunctions::ID = 0;
-INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false);
+namespace {
+
+/// ComparableFunction - A struct that pairs together functions with a
+/// TargetData so that we can keep them together as elements in the DenseSet.
+class ComparableFunction {
+public:
+ static const ComparableFunction EmptyKey;
+ static const ComparableFunction TombstoneKey;
+ static TargetData * const LookupOnly;
+
+ ComparableFunction(Function *Func, TargetData *TD)
+ : Func(Func), Hash(profileFunction(Func)), TD(TD) {}
+
+ Function *getFunc() const { return Func; }
+ unsigned getHash() const { return Hash; }
+ TargetData *getTD() const { return TD; }
+
+ // 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 = NULL;
+ }
+
+private:
+ explicit ComparableFunction(unsigned Hash)
+ : Func(NULL), Hash(Hash), TD(NULL) {}
+
+ AssertingVH<Function> Func;
+ unsigned Hash;
+ TargetData *TD;
+};
+
+const ComparableFunction ComparableFunction::EmptyKey = ComparableFunction(0);
+const ComparableFunction ComparableFunction::TombstoneKey =
+ ComparableFunction(1);
+TargetData * const ComparableFunction::LookupOnly = (TargetData*)(-1);
-ModulePass *llvm::createMergeFunctionsPass() {
- return new MergeFunctions();
+}
+
+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. TargetData is
/// used if available. The comparator always fails conservatively (erring on the
@@ -111,34 +156,34 @@ class FunctionComparator {
public:
FunctionComparator(const TargetData *TD, const Function *F1,
const Function *F2)
- : F1(F1), F2(F2), TD(TD), IDMap1Count(0), IDMap2Count(0) {}
+ : F1(F1), F2(F2), TD(TD) {}
- /// Compare - test whether the two functions have equivalent behaviour.
- bool Compare();
+ /// Test whether the two functions have equivalent behaviour.
+ bool compare();
private:
- /// Compare - test whether two basic blocks have equivalent behaviour.
- bool Compare(const BasicBlock *BB1, const BasicBlock *BB2);
+ /// Test whether two basic blocks have equivalent behaviour.
+ bool compare(const BasicBlock *BB1, const BasicBlock *BB2);
- /// Enumerate - 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.
- bool Enumerate(const Value *V1, const Value *V2);
+ /// 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.
+ bool enumerate(const Value *V1, const Value *V2);
- /// isEquivalentOperation - Compare two Instructions for equivalence, similar
- /// to Instruction::isSameOperationAs but with modifications to the type
+ /// 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;
- /// isEquivalentGEP - Compare two GEPs for equivalent pointer arithmetic.
+ /// 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));
}
- /// isEquivalentType - Compare two Types, treating all pointer types as equal.
+ /// Compare two Types, treating all pointer types as equal.
bool isEquivalentType(const Type *Ty1, const Type *Ty2) const;
// The two functions undergoing comparison.
@@ -146,20 +191,26 @@ private:
const TargetData *TD;
- typedef DenseMap<const Value *, unsigned long> IDMap;
- IDMap Map1, Map2;
- unsigned long IDMap1Count, IDMap2Count;
+ DenseMap<const Value *, const Value *> id_map;
+ DenseSet<const Value *> seen_values;
};
+
}
-/// isEquivalentType - any two pointers in the same address space are
-/// equivalent. Otherwise, standard type equivalence rules apply.
+// Any two pointers in the same address space are equivalent, intptr_t and
+// pointers are equivalent. Otherwise, standard type equivalence rules apply.
bool FunctionComparator::isEquivalentType(const Type *Ty1,
const Type *Ty2) const {
if (Ty1 == Ty2)
return true;
- if (Ty1->getTypeID() != Ty2->getTypeID())
+ if (Ty1->getTypeID() != Ty2->getTypeID()) {
+ if (TD) {
+ LLVMContext &Ctx = Ty1->getContext();
+ if (isa<PointerType>(Ty1) && Ty2 == TD->getIntPtrType(Ctx)) return true;
+ if (isa<PointerType>(Ty2) && Ty1 == TD->getIntPtrType(Ctx)) return true;
+ }
return false;
+ }
switch(Ty1->getTypeID()) {
default:
@@ -167,6 +218,7 @@ bool FunctionComparator::isEquivalentType(const Type *Ty1,
// Fall through in Release mode.
case Type::IntegerTyID:
case Type::OpaqueTyID:
+ case Type::VectorTyID:
// Ty1 == Ty2 would have returned true earlier.
return false;
@@ -225,21 +277,18 @@ bool FunctionComparator::isEquivalentType(const Type *Ty1,
return ATy1->getNumElements() == ATy2->getNumElements() &&
isEquivalentType(ATy1->getElementType(), ATy2->getElementType());
}
-
- case Type::VectorTyID: {
- const VectorType *VTy1 = cast<VectorType>(Ty1);
- const VectorType *VTy2 = cast<VectorType>(Ty2);
- return VTy1->getNumElements() == VTy2->getNumElements() &&
- isEquivalentType(VTy1->getElementType(), VTy2->getElementType());
- }
}
}
-/// isEquivalentOperation - 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.
+// 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()) ||
@@ -263,14 +312,11 @@ bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
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->isTailCall() == cast<CallInst>(I2)->isTailCall() &&
- CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
- CI->getAttributes().getRawPointer() ==
- cast<CallInst>(I2)->getAttributes().getRawPointer();
+ 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().getRawPointer() ==
- cast<InvokeInst>(I2)->getAttributes().getRawPointer();
+ CI->getAttributes() == cast<InvokeInst>(I2)->getAttributes();
if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1)) {
if (IVI->getNumIndices() != cast<InsertValueInst>(I2)->getNumIndices())
return false;
@@ -291,8 +337,7 @@ bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
return true;
}
-/// isEquivalentGEP - determine whether two GEP operations perform the same
-/// underlying arithmetic.
+// Determine whether two GEP operations perform the same underlying arithmetic.
bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1,
const GEPOperator *GEP2) {
// When we have target data, we can reduce the GEP down to the value in bytes
@@ -315,17 +360,17 @@ bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1,
return false;
for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) {
- if (!Enumerate(GEP1->getOperand(i), GEP2->getOperand(i)))
+ if (!enumerate(GEP1->getOperand(i), GEP2->getOperand(i)))
return false;
}
return true;
}
-/// Enumerate - 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.
-bool FunctionComparator::Enumerate(const Value *V1, const Value *V2) {
+// 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.
+bool FunctionComparator::enumerate(const Value *V1, const Value *V2) {
// Check for function @f1 referring to itself and function @f2 referring to
// itself, or referring to each other, or both referring to either of them.
// They're all equivalent if the two functions are otherwise equivalent.
@@ -334,35 +379,44 @@ bool FunctionComparator::Enumerate(const Value *V1, const Value *V2) {
if (V1 == F2 && V2 == F1)
return true;
- // TODO: constant expressions with GEP or references to F1 or F2.
- if (isa<Constant>(V1))
- return V1 == V2;
-
- if (isa<InlineAsm>(V1) && isa<InlineAsm>(V2)) {
- const InlineAsm *IA1 = cast<InlineAsm>(V1);
- const InlineAsm *IA2 = cast<InlineAsm>(V2);
- return IA1->getAsmString() == IA2->getAsmString() &&
- IA1->getConstraintString() == IA2->getConstraintString();
+ if (const Constant *C1 = dyn_cast<Constant>(V1)) {
+ if (V1 == V2) return true;
+ const Constant *C2 = dyn_cast<Constant>(V2);
+ if (!C2) return false;
+ // TODO: constant expressions with GEP or references to F1 or F2.
+ if (C1->isNullValue() && C2->isNullValue() &&
+ isEquivalentType(C1->getType(), C2->getType()))
+ return true;
+ // Try bitcasting C2 to C1's type. If the bitcast is legal and returns C1
+ // then they must have equal bit patterns.
+ return C1->getType()->canLosslesslyBitCastTo(C2->getType()) &&
+ C1 == ConstantExpr::getBitCast(const_cast<Constant*>(C2), C1->getType());
}
- unsigned long &ID1 = Map1[V1];
- if (!ID1)
- ID1 = ++IDMap1Count;
+ if (isa<InlineAsm>(V1) || isa<InlineAsm>(V2))
+ return V1 == V2;
- unsigned long &ID2 = Map2[V2];
- if (!ID2)
- ID2 = ++IDMap2Count;
+ // Check that V1 maps to V2. If we find a value that V1 maps to then we simply
+ // check whether it's equal to V2. When there is no mapping then we need to
+ // ensure that V2 isn't already equivalent to something else. For this
+ // purpose, we track the V2 values in a set.
- return ID1 == ID2;
+ const Value *&map_elem = id_map[V1];
+ if (map_elem)
+ return map_elem == V2;
+ if (!seen_values.insert(V2).second)
+ return false;
+ map_elem = V2;
+ return true;
}
-/// Compare - test whether two basic blocks have equivalent behaviour.
-bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) {
+// 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))
+ if (!enumerate(F1I, F2I))
return false;
if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) {
@@ -370,7 +424,7 @@ bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) {
if (!GEP2)
return false;
- if (!Enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
+ if (!enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
return false;
if (!isEquivalentGEP(GEP1, GEP2))
@@ -384,7 +438,7 @@ bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) {
Value *OpF1 = F1I->getOperand(i);
Value *OpF2 = F2I->getOperand(i);
- if (!Enumerate(OpF1, OpF2))
+ if (!enumerate(OpF1, OpF2))
return false;
if (OpF1->getValueID() != OpF2->getValueID() ||
@@ -399,8 +453,8 @@ bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) {
return F1I == F1E && F2I == F2E;
}
-/// Compare - test whether the two functions have equivalent behaviour.
-bool FunctionComparator::Compare() {
+// 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.
@@ -431,14 +485,14 @@ bool FunctionComparator::Compare() {
return false;
assert(F1->arg_size() == F2->arg_size() &&
- "Identical functions have a different number of args.");
+ "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");
+ if (!enumerate(f1i, f2i))
+ llvm_unreachable("Arguments repeat!");
}
// We do a CFG-ordered walk since the actual ordering of the blocks in the
@@ -456,7 +510,7 @@ bool FunctionComparator::Compare() {
const BasicBlock *F1BB = F1BBs.pop_back_val();
const BasicBlock *F2BB = F2BBs.pop_back_val();
- if (!Enumerate(F1BB, F2BB) || !Compare(F1BB, F2BB))
+ if (!enumerate(F1BB, F2BB) || !compare(F1BB, F2BB))
return false;
const TerminatorInst *F1TI = F1BB->getTerminator();
@@ -474,23 +528,190 @@ bool FunctionComparator::Compare() {
return true;
}
-/// WriteThunk - Replace G with a simple tail call to bitcast(F). Also replace
-/// direct uses of G with bitcast(F).
-void MergeFunctions::WriteThunk(Function *F, Function *G) const {
+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.
- Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
- for (Value::use_iterator UI = G->use_begin(), UE = G->use_end();
- UI != UE;) {
- Value::use_iterator TheIter = UI;
- ++UI;
- CallSite CS(*TheIter);
- if (CS && CS.isCallee(TheIter))
- TheIter.getUse().set(BitcastF);
- }
+ replaceDirectCallers(G, F);
}
- // If G was internal then we may have replaced all uses if G with F. If so,
+ // 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();
@@ -522,131 +743,126 @@ void MergeFunctions::WriteThunk(Function *F, Function *G) const {
NewG->copyAttributesFrom(G);
NewG->takeName(G);
+ removeUsers(G);
G->replaceAllUsesWith(NewG);
G->eraseFromParent();
+
+ DEBUG(dbgs() << "writeThunk: " << NewG->getName() << '\n');
+ ++NumThunksWritten;
}
-/// MergeTwoFunctions - Merge two equivalent functions. Upon completion,
-/// Function G is deleted.
-void MergeFunctions::MergeTwoFunctions(Function *F, Function *G) const {
- if (F->isWeakForLinker()) {
- assert(G->isWeakForLinker());
+// 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);
- // 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);
- F->replaceAllUsesWith(H);
+ unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
- unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
+ writeAlias(F, G);
+ writeAlias(F, H);
- WriteThunk(F, G);
- WriteThunk(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);
+ }
- F->setAlignment(MaxAlignment);
- F->setLinkage(GlobalValue::InternalLinkage);
+ ++NumDoubleWeak;
} else {
- WriteThunk(F, G);
+ writeThunkOrAlias(F, G);
}
++NumFunctionsMerged;
}
-static unsigned ProfileFunction(const Function *F) {
- const FunctionType *FTy = F->getFunctionType();
-
- FoldingSetNodeID ID;
- ID.AddInteger(F->size());
- ID.AddInteger(F->getCallingConv());
- ID.AddBoolean(F->hasGC());
- ID.AddBoolean(FTy->isVarArg());
- ID.AddInteger(FTy->getReturnType()->getTypeID());
- for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
- ID.AddInteger(FTy->getParamType(i)->getTypeID());
- return ID.ComputeHash();
-}
-
-class ComparableFunction {
-public:
- ComparableFunction(Function *Func, TargetData *TD)
- : Func(Func), Hash(ProfileFunction(Func)), TD(TD) {}
+// 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;
+ }
- AssertingVH<Function> const Func;
- const unsigned Hash;
- TargetData * const TD;
-};
+ const ComparableFunction &OldF = *Result.first;
-struct MergeFunctionsEqualityInfo {
- static ComparableFunction *getEmptyKey() {
- return reinterpret_cast<ComparableFunction*>(0);
- }
- static ComparableFunction *getTombstoneKey() {
- return reinterpret_cast<ComparableFunction*>(-1);
- }
- static unsigned getHashValue(const ComparableFunction *CF) {
- return CF->Hash;
- }
- static bool isEqual(const ComparableFunction *LHS,
- const ComparableFunction *RHS) {
- if (LHS == RHS)
- return true;
- if (LHS == getEmptyKey() || LHS == getTombstoneKey() ||
- RHS == getEmptyKey() || RHS == getTombstoneKey())
- return false;
- assert(LHS->TD == RHS->TD && "Comparing functions for different targets");
- return FunctionComparator(LHS->TD, LHS->Func, RHS->Func).Compare();
- }
-};
+ // Never thunk a strong function to a weak function.
+ assert(!OldF.getFunc()->mayBeOverridden() ||
+ NewF.getFunc()->mayBeOverridden());
-bool MergeFunctions::runOnModule(Module &M) {
- typedef DenseSet<ComparableFunction *, MergeFunctionsEqualityInfo> FnSetType;
+ DEBUG(dbgs() << " " << OldF.getFunc()->getName() << " == "
+ << NewF.getFunc()->getName() << '\n');
- bool Changed = false;
- TD = getAnalysisIfAvailable<TargetData>();
+ Function *DeleteF = NewF.getFunc();
+ NewF.release();
+ mergeTwoFunctions(OldF.getFunc(), DeleteF);
+ return true;
+}
- std::vector<Function *> Funcs;
- for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
- if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage())
- Funcs.push_back(F);
+// 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);
}
+}
- bool LocalChanged;
- do {
- LocalChanged = false;
-
- FnSetType FnSet;
- for (unsigned i = 0, e = Funcs.size(); i != e;) {
- Function *F = Funcs[i];
- ComparableFunction *NewF = new ComparableFunction(F, TD);
- std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF);
- if (!Result.second) {
- ComparableFunction *&OldF = *Result.first;
- assert(OldF && "Expected a hash collision");
-
- // NewF will be deleted in favour of OldF unless NewF is strong and
- // OldF is weak in which case swap them to keep the strong definition.
-
- if (OldF->Func->isWeakForLinker() && !NewF->Func->isWeakForLinker())
- std::swap(OldF, NewF);
-
- DEBUG(dbgs() << " " << OldF->Func->getName() << " == "
- << NewF->Func->getName() << '\n');
-
- Funcs.erase(Funcs.begin() + i);
- --e;
-
- Function *DeleteF = NewF->Func;
- delete NewF;
- MergeTwoFunctions(OldF->Func, DeleteF);
- LocalChanged = true;
- Changed = true;
- } else {
- ++i;
+// 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);
}
}
- DeleteContainerPointers(FnSet);
- } while (LocalChanged);
-
- return Changed;
+ }
}
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