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Fix many bugs when merging weak-strong and weak-weak pairs. We now merge all
strong functions first to make sure they're the canonical definitions and then do a second pass looking only for weak functions. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113104 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky
parent
beac75da37
commit
b0104e1bb5
@ -69,32 +69,79 @@ using namespace llvm;
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STATISTIC(NumFunctionsMerged, "Number of functions merged");
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namespace {
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/// MergeFunctions finds functions which will generate identical machine code,
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/// by considering all pointer types to be equivalent. Once identified,
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/// MergeFunctions will fold them by replacing a call to one to a call to a
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/// bitcast of the other.
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///
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class MergeFunctions : public ModulePass {
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public:
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static char ID;
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MergeFunctions() : ModulePass(ID) {}
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bool runOnModule(Module &M);
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static unsigned ProfileFunction(const Function *F) {
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const FunctionType *FTy = F->getFunctionType();
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private:
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/// MergeTwoFunctions - Merge two equivalent functions. Upon completion, G
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/// may be deleted, or may be converted into a thunk. In either case, it
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/// should never be visited again.
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void MergeTwoFunctions(Function *F, Function *G) const;
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/// WriteThunk - Replace G with a simple tail call to bitcast(F). Also
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/// replace direct uses of G with bitcast(F).
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void WriteThunk(Function *F, Function *G) const;
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TargetData *TD;
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};
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FoldingSetNodeID ID;
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ID.AddInteger(F->size());
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ID.AddInteger(F->getCallingConv());
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ID.AddBoolean(F->hasGC());
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ID.AddBoolean(FTy->isVarArg());
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ID.AddInteger(FTy->getReturnType()->getTypeID());
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for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
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ID.AddInteger(FTy->getParamType(i)->getTypeID());
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return ID.ComputeHash();
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}
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class ComparableFunction {
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public:
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ComparableFunction(Function *Func, TargetData *TD)
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: Func(Func), Hash(ProfileFunction(Func)), TD(TD) {}
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AssertingVH<Function> const Func;
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const unsigned Hash;
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TargetData * const TD;
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};
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struct MergeFunctionsEqualityInfo {
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static ComparableFunction *getEmptyKey() {
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return reinterpret_cast<ComparableFunction*>(0);
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}
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static ComparableFunction *getTombstoneKey() {
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return reinterpret_cast<ComparableFunction*>(-1);
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}
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static unsigned getHashValue(const ComparableFunction *CF) {
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return CF->Hash;
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}
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static bool isEqual(const ComparableFunction *LHS,
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const ComparableFunction *RHS);
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};
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/// MergeFunctions finds functions which will generate identical machine code,
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/// by considering all pointer types to be equivalent. Once identified,
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/// MergeFunctions will fold them by replacing a call to one to a call to a
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/// bitcast of the other.
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///
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class MergeFunctions : public ModulePass {
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public:
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static char ID;
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MergeFunctions() : ModulePass(ID) {}
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bool runOnModule(Module &M);
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private:
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typedef DenseSet<ComparableFunction *, MergeFunctionsEqualityInfo> FnSetType;
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/// Insert a ComparableFunction into the FnSet, or merge it away if it's
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/// equal to one that's already present.
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bool Insert(FnSetType &FnSet, ComparableFunction *NewF);
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/// MergeTwoFunctions - Merge two equivalent functions. Upon completion, G
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/// may be deleted, or may be converted into a thunk. In either case, it
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/// should never be visited again.
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void MergeTwoFunctions(Function *F, Function *G) const;
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/// WriteThunk - Replace G with a simple tail call to bitcast(F). Also
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/// replace direct uses of G with bitcast(F). Deletes G.
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void WriteThunk(Function *F, Function *G) const;
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TargetData *TD;
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};
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} // end anonymous namespace
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char MergeFunctions::ID = 0;
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INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false);
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@ -475,7 +522,7 @@ bool FunctionComparator::Compare() {
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}
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/// WriteThunk - Replace G with a simple tail call to bitcast(F). Also replace
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/// direct uses of G with bitcast(F).
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/// direct uses of G with bitcast(F). Deletes G.
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void MergeFunctions::WriteThunk(Function *F, Function *G) const {
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if (!G->mayBeOverridden()) {
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// Redirect direct callers of G to F.
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@ -553,100 +600,138 @@ void MergeFunctions::MergeTwoFunctions(Function *F, Function *G) const {
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++NumFunctionsMerged;
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}
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static unsigned ProfileFunction(const Function *F) {
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const FunctionType *FTy = F->getFunctionType();
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// Insert - Insert a ComparableFunction into the FnSet, or merge it away if
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// equal to one that's already inserted.
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bool MergeFunctions::Insert(FnSetType &FnSet, ComparableFunction *NewF) {
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std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF);
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if (Result.second)
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return false;
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FoldingSetNodeID ID;
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ID.AddInteger(F->size());
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ID.AddInteger(F->getCallingConv());
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ID.AddBoolean(F->hasGC());
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ID.AddBoolean(FTy->isVarArg());
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ID.AddInteger(FTy->getReturnType()->getTypeID());
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for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
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ID.AddInteger(FTy->getParamType(i)->getTypeID());
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return ID.ComputeHash();
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ComparableFunction *OldF = *Result.first;
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assert(OldF && "Expected a hash collision");
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// Never thunk a strong function to a weak function.
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assert(!OldF->Func->isWeakForLinker() || NewF->Func->isWeakForLinker());
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DEBUG(dbgs() << " " << OldF->Func->getName() << " == "
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<< NewF->Func->getName() << '\n');
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Function *DeleteF = NewF->Func;
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delete NewF;
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MergeTwoFunctions(OldF->Func, DeleteF);
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return true;
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}
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class ComparableFunction {
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public:
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ComparableFunction(Function *Func, TargetData *TD)
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: Func(Func), Hash(ProfileFunction(Func)), TD(TD) {}
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// IsThunk - This method determines whether or not a given Function is a thunk\// like the ones emitted by this pass and therefore not subject to further
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// merging.
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static bool IsThunk(const Function *F) {
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// The safe direction to fail is to return true. In that case, the function
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// will be removed from merging analysis. If we failed to including functions
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// then we may try to merge unmergable thing (ie., identical weak functions)
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// which will push us into an infinite loop.
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AssertingVH<Function> const Func;
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const unsigned Hash;
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TargetData * const TD;
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};
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if (F->size() != 1)
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return false;
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struct MergeFunctionsEqualityInfo {
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static ComparableFunction *getEmptyKey() {
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return reinterpret_cast<ComparableFunction*>(0);
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const BasicBlock *BB = &F->front();
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// A thunk is:
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// bitcast-inst*
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// optional-reg tail call @thunkee(args...*)
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// ret void|optional-reg
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// where the args are in the same order as the arguments.
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// Verify that the sequence of bitcast-inst's are all casts of arguments and
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// that there aren't any extras (ie. no repeated casts).
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int LastArgNo = -1;
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BasicBlock::const_iterator I = BB->begin();
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while (const BitCastInst *BCI = dyn_cast<BitCastInst>(I)) {
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const Argument *A = dyn_cast<Argument>(BCI->getOperand(0));
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if (!A) return false;
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if ((int)A->getArgNo() >= LastArgNo) return false;
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LastArgNo = A->getArgNo();
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++I;
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}
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static ComparableFunction *getTombstoneKey() {
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return reinterpret_cast<ComparableFunction*>(-1);
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// Verify that the call instruction has the same arguments as this function
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// and that they're all either the incoming argument or a cast of the right
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// argument.
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const CallInst *CI = dyn_cast<CallInst>(I++);
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if (!CI || !CI->isTailCall() ||
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CI->getNumArgOperands() != F->arg_size()) return false;
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for (unsigned i = 0, e = CI->getNumArgOperands(); i != e; ++i) {
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const Value *V = CI->getArgOperand(i);
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const Argument *A = dyn_cast<Argument>(V);
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if (!A) {
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const BitCastInst *BCI = dyn_cast<BitCastInst>(V);
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if (!BCI) return false;
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A = cast<Argument>(BCI->getOperand(0));
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}
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if (A->getArgNo() != i) return false;
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}
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static unsigned getHashValue(const ComparableFunction *CF) {
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return CF->Hash;
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// Verify that the terminator is a ret void (if we're void) or a ret of the
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// call's return, or a ret of a bitcast of the call's return.
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const Value *RetOp = CI;
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if (const BitCastInst *BCI = dyn_cast<BitCastInst>(I)) {
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++I;
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if (BCI->getOperand(0) != CI) return false;
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RetOp = BCI;
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}
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static bool isEqual(const ComparableFunction *LHS,
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const ComparableFunction *RHS) {
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if (LHS == RHS)
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return true;
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if (LHS == getEmptyKey() || LHS == getTombstoneKey() ||
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RHS == getEmptyKey() || RHS == getTombstoneKey())
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return false;
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assert(LHS->TD == RHS->TD && "Comparing functions for different targets");
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return FunctionComparator(LHS->TD, LHS->Func, RHS->Func).Compare();
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}
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};
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const ReturnInst *RI = dyn_cast<ReturnInst>(I);
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if (!RI) return false;
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if (RI->getNumOperands() == 0)
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return CI->getType()->isVoidTy();
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return RI->getReturnValue() == CI;
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}
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bool MergeFunctions::runOnModule(Module &M) {
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typedef DenseSet<ComparableFunction *, MergeFunctionsEqualityInfo> FnSetType;
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bool Changed = false;
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TD = getAnalysisIfAvailable<TargetData>();
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std::vector<Function *> Funcs;
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for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
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if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage())
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Funcs.push_back(F);
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}
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bool LocalChanged;
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do {
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DEBUG(dbgs() << "size: " << M.size() << '\n');
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LocalChanged = false;
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FnSetType FnSet;
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for (unsigned i = 0, e = Funcs.size(); i != e;) {
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Function *F = Funcs[i];
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ComparableFunction *NewF = new ComparableFunction(F, TD);
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std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF);
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if (!Result.second) {
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ComparableFunction *&OldF = *Result.first;
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assert(OldF && "Expected a hash collision");
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// NewF will be deleted in favour of OldF unless NewF is strong and
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// OldF is weak in which case swap them to keep the strong definition.
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// Insert only strong functions and merge them. Strong function merging
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// always deletes one of them.
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for (Module::iterator I = M.begin(), E = M.end(); I != E;) {
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Function *F = I++;
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if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
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!F->isWeakForLinker() && !IsThunk(F)) {
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ComparableFunction *CF = new ComparableFunction(F, TD);
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LocalChanged |= Insert(FnSet, CF);
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}
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}
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if (OldF->Func->isWeakForLinker() && !NewF->Func->isWeakForLinker())
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std::swap(OldF, NewF);
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DEBUG(dbgs() << " " << OldF->Func->getName() << " == "
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<< NewF->Func->getName() << '\n');
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Funcs.erase(Funcs.begin() + i);
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--e;
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Function *DeleteF = NewF->Func;
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delete NewF;
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MergeTwoFunctions(OldF->Func, DeleteF);
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LocalChanged = true;
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Changed = true;
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} else {
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++i;
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// Insert only weak functions and merge them. By doing these second we
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// create thunks to the strong function when possible. When two weak
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// functions are identical, we create a new strong function with two weak
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// weak thunks to it which are identical but not mergable.
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for (Module::iterator I = M.begin(), E = M.end(); I != E;) {
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Function *F = I++;
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if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
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F->isWeakForLinker() && !IsThunk(F)) {
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ComparableFunction *CF = new ComparableFunction(F, TD);
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LocalChanged |= Insert(FnSet, CF);
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}
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}
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DeleteContainerPointers(FnSet);
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Changed |= LocalChanged;
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} while (LocalChanged);
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return Changed;
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}
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bool MergeFunctionsEqualityInfo::isEqual(const ComparableFunction *LHS,
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const ComparableFunction *RHS) {
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if (LHS == RHS)
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return true;
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if (LHS == getEmptyKey() || LHS == getTombstoneKey() ||
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RHS == getEmptyKey() || RHS == getTombstoneKey())
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return false;
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assert(LHS->TD == RHS->TD && "Comparing functions for different targets");
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return FunctionComparator(LHS->TD, LHS->Func, RHS->Func).Compare();
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}
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