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-rw-r--r--lib/Transforms/IPO/MergeFunctions.cpp293
1 files changed, 164 insertions, 129 deletions
diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index 3b28d27820..d084b2a075 100644
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -31,13 +31,8 @@
// 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 implementations.
//
-// * use SCC to cut down on pair-wise comparisons and solve larger cycles.
-//
-// The current implementation loops over a pair-wise comparison of all
-// functions in the program where the two functions in the pair are treated as
-// assumed to be equal until proven otherwise. We could both use fewer
-// comparisons and optimize more complex cases if we used strongly connected
-// components of the call graph.
+// * switch from n^2 pair-wise comparisons to an n-way comparison for each
+// bucket.
//
// * be smarter about bitcast.
//
@@ -47,11 +42,12 @@
// other doesn't. We should learn to peer through bitcasts without imposing bad
// performance properties.
//
-// * don't emit aliases for Mach-O.
+// * emit aliases for ELF
//
-// Mach-O doesn't support aliases which means that we must avoid introducing
-// them in the bitcode on architectures which don't support them, such as
-// Mac OSX. There's a few approaches to this problem;
+// ELF supports symbol aliases which are represented with GlobalAlias in the
+// Module, and we could emit them in the case that the addresses don't need to
+// be distinct. The problem is that not all object formats support equivalent
+// functionality. There's a few approaches to this problem;
// a) teach codegen to lower global aliases to thunks on platforms which don't
// support them.
// b) always emit thunks, and create a separate thunk-to-alias pass which
@@ -85,28 +81,16 @@ using namespace llvm;
STATISTIC(NumFunctionsMerged, "Number of functions merged");
namespace {
- class MergeFunctions : public ModulePass {
- public:
+ /// 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.
+ ///
+ struct MergeFunctions : public ModulePass {
static char ID; // Pass identification, replacement for typeid
MergeFunctions() : ModulePass(&ID) {}
bool runOnModule(Module &M);
-
- private:
- bool isEquivalentGEP(const GetElementPtrInst *GEP1,
- const GetElementPtrInst *GEP2);
-
- bool equals(const BasicBlock *BB1, const BasicBlock *BB2);
- bool equals(const Function *F, const Function *G);
-
- bool compare(const Value *V1, const Value *V2);
-
- const Function *LHS, *RHS;
- typedef DenseMap<const Value *, unsigned long> IDMap;
- IDMap Map;
- DenseMap<const Function *, IDMap> Domains;
- DenseMap<const Function *, unsigned long> DomainCount;
- TargetData *TD;
};
}
@@ -120,8 +104,60 @@ ModulePass *llvm::createMergeFunctionsPass() {
// ===----------------------------------------------------------------------===
// Comparison of functions
// ===----------------------------------------------------------------------===
+namespace {
+class FunctionComparator {
+public:
+ FunctionComparator(TargetData *TD, Function *F1, Function *F2)
+ : TD(TD), F1(F1), F2(F2) {}
+
+ // 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);
+
+ // getDomain - a value's domain is its parent function if it is specific to a
+ // function, or NULL otherwise.
+ const Function *getDomain(const Value *V) const;
+
+ // 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);
+
+ // isEquivalentOperation - 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.
+ bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2);
+ bool isEquivalentGEP(const GetElementPtrInst *GEP1,
+ const GetElementPtrInst *GEP2) {
+ return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2));
+ }
-static unsigned long hash(const Function *F) {
+ // isEquivalentType - Compare two Types, treating all pointer types as equal.
+ bool isEquivalentType(const Type *Ty1, const Type *Ty2) const;
+
+ // The two functions undergoing comparison.
+ Function *F1, *F2;
+
+ TargetData *TD;
+
+ typedef DenseMap<const Value *, unsigned long> IDMap;
+ IDMap Map;
+ DenseMap<const Function *, IDMap> Domains;
+ DenseMap<const Function *, unsigned long> DomainCount;
+};
+}
+
+/// Compute a number which is guaranteed to be equal for two equivalent
+/// functions, but is very likely to be different for different functions. This
+/// needs to be computed as efficiently as possible.
+static unsigned long ProfileFunction(const Function *F) {
const FunctionType *FTy = F->getFunctionType();
FoldingSetNodeID ID;
@@ -137,7 +173,8 @@ static unsigned long hash(const Function *F) {
/// isEquivalentType - any two pointers are equivalent. Otherwise, standard
/// type equivalence rules apply.
-static bool isEquivalentType(const Type *Ty1, const Type *Ty2) {
+bool FunctionComparator::isEquivalentType(const Type *Ty1,
+ const Type *Ty2) const {
if (Ty1 == Ty2)
return true;
if (Ty1->getTypeID() != Ty2->getTypeID())
@@ -234,8 +271,8 @@ static bool isEquivalentType(const Type *Ty1, const Type *Ty2) {
/// 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.
-static bool
-isEquivalentOperation(const Instruction *I1, const Instruction *I2) {
+bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
+ const Instruction *I2) const {
if (I1->getOpcode() != I2->getOpcode() ||
I1->getNumOperands() != I2->getNumOperands() ||
!isEquivalentType(I1->getType(), I2->getType()) ||
@@ -287,18 +324,15 @@ isEquivalentOperation(const Instruction *I1, const Instruction *I2) {
return true;
}
-bool MergeFunctions::isEquivalentGEP(const GetElementPtrInst *GEP1,
- const GetElementPtrInst *GEP2) {
+/// isEquivalentGEP - 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
+ // added to the address.
if (TD && GEP1->hasAllConstantIndices() && GEP2->hasAllConstantIndices()) {
- SmallVector<Value *, 8> Indices1, Indices2;
- for (GetElementPtrInst::const_op_iterator I = GEP1->idx_begin(),
- E = GEP1->idx_end(); I != E; ++I) {
- Indices1.push_back(*I);
- }
- for (GetElementPtrInst::const_op_iterator I = GEP2->idx_begin(),
- E = GEP2->idx_end(); I != E; ++I) {
- Indices2.push_back(*I);
- }
+ SmallVector<Value *, 8> Indices1(GEP1->idx_begin(), GEP1->idx_end());
+ SmallVector<Value *, 8> Indices2(GEP2->idx_begin(), GEP2->idx_end());
uint64_t Offset1 = TD->getIndexedOffset(GEP1->getPointerOperandType(),
Indices1.data(), Indices1.size());
uint64_t Offset2 = TD->getIndexedOffset(GEP2->getPointerOperandType(),
@@ -306,7 +340,6 @@ bool MergeFunctions::isEquivalentGEP(const GetElementPtrInst *GEP1,
return Offset1 == Offset2;
}
- // Equivalent types aren't enough.
if (GEP1->getPointerOperand()->getType() !=
GEP2->getPointerOperand()->getType())
return false;
@@ -315,19 +348,38 @@ bool MergeFunctions::isEquivalentGEP(const GetElementPtrInst *GEP1,
return false;
for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) {
- if (!compare(GEP1->getOperand(i), GEP2->getOperand(i)))
+ if (!Enumerate(GEP1->getOperand(i), GEP2->getOperand(i)))
return false;
}
return true;
}
-bool MergeFunctions::compare(const Value *V1, const Value *V2) {
- if (V1 == LHS || V1 == RHS)
- if (V2 == LHS || V2 == RHS)
+/// getDomain - a value's domain is its parent function if it is specific to a
+/// function, or NULL otherwise.
+const Function *FunctionComparator::getDomain(const Value *V) const {
+ if (const Argument *A = dyn_cast<Argument>(V)) {
+ return A->getParent();
+ } else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
+ return BB->getParent();
+ } else if (const Instruction *I = dyn_cast<Instruction>(V)) {
+ return I->getParent()->getParent();
+ }
+ return NULL;
+}
+
+/// 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) {
+ // 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.
+ if (V1 == F1 || V1 == F2)
+ if (V2 == F1 || V2 == F2)
return true;
- // TODO: constant expressions in terms of LHS and RHS
+ // TODO: constant expressions with GEP or references to F1 or F2.
if (isa<Constant>(V1))
return V1 == V2;
@@ -340,28 +392,13 @@ bool MergeFunctions::compare(const Value *V1, const Value *V2) {
// We enumerate constants globally and arguments, basic blocks or
// instructions within the function they belong to.
- const Function *Domain1 = NULL;
- if (const Argument *A = dyn_cast<Argument>(V1)) {
- Domain1 = A->getParent();
- } else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V1)) {
- Domain1 = BB->getParent();
- } else if (const Instruction *I = dyn_cast<Instruction>(V1)) {
- Domain1 = I->getParent()->getParent();
- }
-
- const Function *Domain2 = NULL;
- if (const Argument *A = dyn_cast<Argument>(V2)) {
- Domain2 = A->getParent();
- } else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V2)) {
- Domain2 = BB->getParent();
- } else if (const Instruction *I = dyn_cast<Instruction>(V2)) {
- Domain2 = I->getParent()->getParent();
- }
+ const Function *Domain1 = getDomain(V1);
+ const Function *Domain2 = getDomain(V2);
+ // The domains have to either be both NULL, or F1, F2.
if (Domain1 != Domain2)
- if (Domain1 != LHS && Domain1 != RHS)
- if (Domain2 != LHS && Domain2 != RHS)
- return false;
+ if (Domain1 != F1 && Domain1 != F2)
+ return false;
IDMap &Map1 = Domains[Domain1];
unsigned long &ID1 = Map1[V1];
@@ -376,116 +413,114 @@ bool MergeFunctions::compare(const Value *V1, const Value *V2) {
return ID1 == ID2;
}
-bool MergeFunctions::equals(const BasicBlock *BB1, const BasicBlock *BB2) {
- BasicBlock::const_iterator FI = BB1->begin(), FE = BB1->end();
- BasicBlock::const_iterator GI = BB2->begin(), GE = BB2->end();
+// Compare - 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 (!compare(FI, GI))
+ if (!Enumerate(F1I, F2I))
return false;
- if (isa<GetElementPtrInst>(FI) && isa<GetElementPtrInst>(GI)) {
- const GetElementPtrInst *GEP1 = cast<GetElementPtrInst>(FI);
- const GetElementPtrInst *GEP2 = cast<GetElementPtrInst>(GI);
+ if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) {
+ const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I);
+ if (!GEP2)
+ return false;
- if (!compare(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
+ if (!Enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
return false;
if (!isEquivalentGEP(GEP1, GEP2))
return false;
} else {
- if (!isEquivalentOperation(FI, GI))
+ if (!isEquivalentOperation(F1I, F2I))
return false;
- for (unsigned i = 0, e = FI->getNumOperands(); i != e; ++i) {
- Value *OpF = FI->getOperand(i);
- Value *OpG = GI->getOperand(i);
+ 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 (!compare(OpF, OpG))
+ if (!Enumerate(OpF1, OpF2))
return false;
- if (OpF->getValueID() != OpG->getValueID() ||
- !isEquivalentType(OpF->getType(), OpG->getType()))
+ if (OpF1->getValueID() != OpF2->getValueID() ||
+ !isEquivalentType(OpF1->getType(), OpF2->getType()))
return false;
}
}
- ++FI, ++GI;
- } while (FI != FE && GI != GE);
+ ++F1I, ++F2I;
+ } while (F1I != F1E && F2I != F2E);
- return FI == FE && GI == GE;
+ return F1I == F1E && F2I == F2E;
}
-bool MergeFunctions::equals(const Function *F, const Function *G) {
+bool FunctionComparator::Compare() {
// We need to recheck everything, but check the things that weren't included
// in the hash first.
- if (F->getAttributes() != G->getAttributes())
+ if (F1->getAttributes() != F2->getAttributes())
return false;
- if (F->hasGC() != G->hasGC())
+ if (F1->hasGC() != F2->hasGC())
return false;
- if (F->hasGC() && F->getGC() != G->getGC())
+ if (F1->hasGC() && F1->getGC() != F2->getGC())
return false;
- if (F->hasSection() != G->hasSection())
+ if (F1->hasSection() != F2->hasSection())
return false;
- if (F->hasSection() && F->getSection() != G->getSection())
+ if (F1->hasSection() && F1->getSection() != F2->getSection())
return false;
- if (F->isVarArg() != G->isVarArg())
+ 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 (F->getCallingConv() != G->getCallingConv())
+ if (F1->getCallingConv() != F2->getCallingConv())
return false;
- if (!isEquivalentType(F->getFunctionType(), G->getFunctionType()))
+ if (!isEquivalentType(F1->getFunctionType(), F2->getFunctionType()))
return false;
- assert(F->arg_size() == G->arg_size() &&
+ assert(F1->arg_size() == F2->arg_size() &&
"Identical functions have a different number of args.");
- LHS = F;
- RHS = G;
-
// Visit the arguments so that they get enumerated in the order they're
// passed in.
- for (Function::const_arg_iterator fi = F->arg_begin(), gi = G->arg_begin(),
- fe = F->arg_end(); fi != fe; ++fi, ++gi) {
- if (!compare(fi, gi))
+ 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");
}
- SmallVector<const BasicBlock *, 8> FBBs, GBBs;
- SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F.
- FBBs.push_back(&F->getEntryBlock());
- GBBs.push_back(&G->getEntryBlock());
- VisitedBBs.insert(FBBs[0]);
- while (!FBBs.empty()) {
- const BasicBlock *FBB = FBBs.pop_back_val();
- const BasicBlock *GBB = GBBs.pop_back_val();
- if (!compare(FBB, GBB) || !equals(FBB, GBB)) {
- Domains.clear();
- DomainCount.clear();
+ // We need to do an 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 *FTI = FBB->getTerminator();
- const TerminatorInst *GTI = GBB->getTerminator();
- assert(FTI->getNumSuccessors() == GTI->getNumSuccessors());
- for (unsigned i = 0, e = FTI->getNumSuccessors(); i != e; ++i) {
- if (!VisitedBBs.insert(FTI->getSuccessor(i)))
+ const TerminatorInst *F1TI = F1BB->getTerminator();
+ const TerminatorInst *F2TI = F2BB->getTerminator();
+ assert(F1TI->getNumSuccessors() == F2TI->getNumSuccessors());
+ for (unsigned i = 0, e = F1TI->getNumSuccessors(); i != e; ++i) {
+ if (!VisitedBBs.insert(F1TI->getSuccessor(i)))
continue;
- FBBs.push_back(FTI->getSuccessor(i));
- GBBs.push_back(GTI->getSuccessor(i));
+ F1BBs.push_back(F1TI->getSuccessor(i));
+ F2BBs.push_back(F2TI->getSuccessor(i));
}
}
-
- Domains.clear();
- DomainCount.clear();
return true;
}
@@ -720,10 +755,10 @@ bool MergeFunctions::runOnModule(Module &M) {
if (F->isDeclaration())
continue;
- FnMap[hash(F)].push_back(F);
+ FnMap[ProfileFunction(F)].push_back(F);
}
- TD = getAnalysisIfAvailable<TargetData>();
+ TargetData *TD = getAnalysisIfAvailable<TargetData>();
bool LocalChanged;
do {
@@ -736,7 +771,7 @@ bool MergeFunctions::runOnModule(Module &M) {
for (int i = 0, e = FnVec.size(); i != e; ++i) {
for (int j = i + 1; j != e; ++j) {
- bool isEqual = equals(FnVec[i], FnVec[j]);
+ bool isEqual = FunctionComparator(TD, FnVec[i], FnVec[j]).Compare();
DEBUG(dbgs() << " " << FnVec[i]->getName()
<< (isEqual ? " == " : " != ")
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-02 01:06:33 +0000