mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-13 04:30:23 +00:00
Change how globalopt handles aliases in llvm.used.
Instead of a custom implementation of replaceAllUsesWith, we just call
replaceAllUsesWith and recreate llvm.used and llvm.compiler-used.
This change is particularity interesting because it makes llvm see
through what clang is doing with static used functions in extern "C"
contexts. With this change, running clang -O2 in
extern "C" {
__attribute__((used)) static void foo() {}
}
produces
@llvm.used = appending global [1 x i8*] [i8* bitcast (void ()* @foo to
i8*)], section "llvm.metadata"
define internal void @foo() #0 {
entry:
ret void
}
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183756 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola
parent
9e26acb5b5
commit
d1b6ca23b4
@ -3041,107 +3041,168 @@ bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
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return true;
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}
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static Value::use_iterator getFirst(Value *V, SmallPtrSet<Use*, 8> &Tried) {
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for (Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
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Use *U = &I.getUse();
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if (Tried.count(U))
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continue;
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/// \brief Given "llvm.used" or "llvm.compiler_used" as a global name, collect
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/// the initializer elements of that global in Set and return the global itself.
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static GlobalVariable *
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collectUsedGlobalVariables(const Module &M, const char *Name,
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SmallPtrSet<GlobalValue *, 8> &Set) {
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GlobalVariable *GV = M.getGlobalVariable(Name);
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if (!GV || !GV->hasInitializer())
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return GV;
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User *Usr = *I;
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GlobalVariable *GV = dyn_cast<GlobalVariable>(Usr);
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if (!GV || !GV->hasName()) {
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Tried.insert(U);
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return I;
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}
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StringRef Name = GV->getName();
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if (Name != "llvm.used" && Name != "llvm.compiler_used") {
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Tried.insert(U);
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return I;
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}
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const ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
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for (unsigned I = 0, E = Init->getNumOperands(); I != E; ++I) {
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Value *Op = Init->getOperand(I);
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GlobalValue *G = cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
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Set.insert(G);
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}
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return V->use_end();
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return GV;
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}
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static bool replaceAllNonLLVMUsedUsesWith(Constant *Old, Constant *New);
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static int compareNames(const void *A, const void *B) {
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const GlobalValue *VA = *reinterpret_cast<GlobalValue* const*>(A);
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const GlobalValue *VB = *reinterpret_cast<GlobalValue* const*>(B);
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if (VA->getName() < VB->getName())
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return -1;
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if (VB->getName() < VA->getName())
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return 1;
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return 0;
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}
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static bool replaceUsesOfWithOnConstant(ConstantArray *CA, Value *From,
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Value *ToV, Use *U) {
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Constant *To = cast<Constant>(ToV);
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static void setUsedInitializer(GlobalVariable &V,
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SmallPtrSet<GlobalValue *, 8> Init) {
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SmallVector<llvm::Constant *, 8> UsedArray;
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PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext());
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SmallVector<Constant*, 8> NewOps;
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for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
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Constant *Op = CA->getOperand(i);
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NewOps.push_back(Op == From ? To : Op);
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for (SmallPtrSet<GlobalValue *, 8>::iterator I = Init.begin(), E = Init.end();
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I != E; ++I) {
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Constant *Cast = llvm::ConstantExpr::getBitCast(*I, Int8PtrTy);
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UsedArray.push_back(Cast);
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}
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// Sort to get deterministic order.
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array_pod_sort(UsedArray.begin(), UsedArray.end(), compareNames);
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ArrayType *ATy = ArrayType::get(Int8PtrTy, UsedArray.size());
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Constant *Replacement = ConstantArray::get(CA->getType(), NewOps);
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assert(Replacement != CA && "CA didn't contain From!");
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bool Ret = replaceAllNonLLVMUsedUsesWith(CA, Replacement);
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if (Replacement->use_empty())
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Replacement->destroyConstant();
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if (CA->use_empty())
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CA->destroyConstant();
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return Ret;
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Module *M = V.getParent();
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V.removeFromParent();
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GlobalVariable *NV =
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new GlobalVariable(*M, ATy, false, llvm::GlobalValue::AppendingLinkage,
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llvm::ConstantArray::get(ATy, UsedArray), "");
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NV->takeName(&V);
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NV->setSection("llvm.metadata");
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delete &V;
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}
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static bool replaceUsesOfWithOnConstant(ConstantExpr *CE, Value *From,
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Value *ToV, Use *U) {
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Constant *To = cast<Constant>(ToV);
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SmallVector<Constant*, 8> NewOps;
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for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
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Constant *Op = CE->getOperand(i);
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NewOps.push_back(Op == From ? To : Op);
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namespace {
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/// \brief An easy to access representation of llvm.used and llvm.compiler_used.
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class LLVMUsed {
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SmallPtrSet<GlobalValue *, 8> Used;
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SmallPtrSet<GlobalValue *, 8> CompilerUsed;
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GlobalVariable *UsedV;
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GlobalVariable *CompilerUsedV;
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public:
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LLVMUsed(const Module &M) {
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UsedV = collectUsedGlobalVariables(M, "llvm.used", Used);
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CompilerUsedV =
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collectUsedGlobalVariables(M, "llvm.compiler_used", CompilerUsed);
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}
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typedef SmallPtrSet<GlobalValue *, 8>::iterator iterator;
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iterator usedBegin() { return Used.begin(); }
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iterator usedEnd() { return Used.end(); }
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iterator compilerUsedBegin() { return CompilerUsed.begin(); }
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iterator compilerUsedEnd() { return CompilerUsed.end(); }
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bool usedCount(GlobalValue *GV) const { return Used.count(GV); }
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bool compilerUsedCount(GlobalValue *GV) const {
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return CompilerUsed.count(GV);
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}
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bool usedErase(GlobalValue *GV) { return Used.erase(GV); }
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bool compilerUsedErase(GlobalValue *GV) { return CompilerUsed.erase(GV); }
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bool usedInsert(GlobalValue *GV) { return Used.insert(GV); }
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bool compilerUsedInsert(GlobalValue *GV) { return CompilerUsed.insert(GV); }
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Constant *Replacement = CE->getWithOperands(NewOps);
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assert(Replacement != CE && "CE didn't contain From!");
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bool Ret = replaceAllNonLLVMUsedUsesWith(CE, Replacement);
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if (Replacement->use_empty())
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Replacement->destroyConstant();
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if (CE->use_empty())
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CE->destroyConstant();
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return Ret;
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void syncVariablesAndSets() {
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if (UsedV)
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setUsedInitializer(*UsedV, Used);
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if (CompilerUsedV)
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setUsedInitializer(*CompilerUsedV, CompilerUsed);
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}
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};
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}
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static bool replaceUsesOfWithOnConstant(Constant *C, Value *From, Value *To,
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Use *U) {
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if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
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return replaceUsesOfWithOnConstant(CA, From, To, U);
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
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return replaceUsesOfWithOnConstant(CE, From, To, U);
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C->replaceUsesOfWithOnConstant(From, To, U);
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return true;
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static bool hasUseOtherThanLLVMUsed(GlobalAlias &GA, const LLVMUsed &U) {
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if (GA.use_empty()) // No use at all.
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return false;
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assert((!U.usedCount(&GA) || !U.compilerUsedCount(&GA)) &&
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"We should have removed the duplicated "
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"element from llvm.compiler_used");
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if (!GA.hasOneUse())
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// Strictly more than one use. So at least one is not in llvm.used and
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// llvm.compiler_used.
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return true;
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// Exactly one use. Check if it is in llvm.used or llvm.compiler_used.
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return !U.usedCount(&GA) && !U.compilerUsedCount(&GA);
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}
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static bool replaceAllNonLLVMUsedUsesWith(Constant *Old, Constant *New) {
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SmallPtrSet<Use*, 8> Tried;
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static bool hasMoreThanOneUseOtherThanLLVMUsed(GlobalValue &V,
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const LLVMUsed &U) {
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unsigned N = 2;
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assert((!U.usedCount(&V) || !U.compilerUsedCount(&V)) &&
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"We should have removed the duplicated "
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"element from llvm.compiler_used");
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if (U.usedCount(&V) || U.compilerUsedCount(&V))
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++N;
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return V.hasNUsesOrMore(N);
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}
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static bool mayHaveOtherReferences(GlobalAlias &GA, const LLVMUsed &U) {
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if (!GA.hasLocalLinkage())
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return true;
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return U.usedCount(&GA) || U.compilerUsedCount(&GA);
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}
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static bool hasUsesToReplace(GlobalAlias &GA, LLVMUsed &U, bool &RenameTarget) {
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RenameTarget = false;
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bool Ret = false;
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for (;;) {
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Value::use_iterator I = getFirst(Old, Tried);
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if (I == Old->use_end())
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break;
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Use &U = I.getUse();
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// Must handle Constants specially, we cannot call replaceUsesOfWith on a
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// constant because they are uniqued.
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if (Constant *C = dyn_cast<Constant>(U.getUser())) {
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if (!isa<GlobalValue>(C)) {
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Ret |= replaceUsesOfWithOnConstant(C, Old, New, &U);
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continue;
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}
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}
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U.set(New);
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if (hasUseOtherThanLLVMUsed(GA, U))
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Ret = true;
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}
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return Ret;
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// If the alias is externally visible, we may still be able to simplify it.
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if (!mayHaveOtherReferences(GA, U))
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return Ret;
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// If the aliasee has internal linkage, give it the name and linkage
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// of the alias, and delete the alias. This turns:
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// define internal ... @f(...)
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// @a = alias ... @f
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// into:
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// define ... @a(...)
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Constant *Aliasee = GA.getAliasee();
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GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
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if (!Target->hasLocalLinkage())
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return Ret;
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// Do not perform the transform if multiple aliases potentially target the
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// aliasee. This check also ensures that it is safe to replace the section
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// and other attributes of the aliasee with those of the alias.
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if (hasMoreThanOneUseOtherThanLLVMUsed(*Target, U))
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return Ret;
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RenameTarget = true;
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return true;
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}
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bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
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bool Changed = false;
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LLVMUsed Used(M);
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for (SmallPtrSet<GlobalValue *, 8>::iterator I = Used.usedBegin(),
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E = Used.usedEnd();
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I != E; ++I)
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Used.compilerUsedErase(*I);
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for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
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I != E;) {
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@ -3156,45 +3217,40 @@ bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
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Constant *Aliasee = J->getAliasee();
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GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
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Target->removeDeadConstantUsers();
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bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
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// Make all users of the alias use the aliasee instead.
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if (replaceAllNonLLVMUsedUsesWith(J, Aliasee)) {
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++NumAliasesResolved;
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Changed = true;
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}
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if (!J->use_empty())
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bool RenameTarget;
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if (!hasUsesToReplace(*J, Used, RenameTarget))
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continue;
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// If the alias is externally visible, we may still be able to simplify it.
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if (!J->hasLocalLinkage()) {
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// If the aliasee has internal linkage, give it the name and linkage
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// of the alias, and delete the alias. This turns:
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// define internal ... @f(...)
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// @a = alias ... @f
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// into:
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// define ... @a(...)
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if (!Target->hasLocalLinkage())
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continue;
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// Do not perform the transform if multiple aliases potentially target the
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// aliasee. This check also ensures that it is safe to replace the section
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// and other attributes of the aliasee with those of the alias.
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if (!hasOneUse)
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continue;
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J->replaceAllUsesWith(Aliasee);
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++NumAliasesResolved;
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Changed = true;
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if (RenameTarget) {
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// Give the aliasee the name, linkage and other attributes of the alias.
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Target->takeName(J);
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Target->setLinkage(J->getLinkage());
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Target->GlobalValue::copyAttributesFrom(J);
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if (Used.usedErase(J))
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Used.usedInsert(Target);
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if (Used.compilerUsedErase(J))
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Used.compilerUsedInsert(Target);
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}
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if (mayHaveOtherReferences(*J, Used))
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continue;
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// Delete the alias.
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M.getAliasList().erase(J);
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++NumAliasesRemoved;
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Changed = true;
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}
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Used.syncVariablesAndSets();
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return Changed;
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}
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@ -2,16 +2,21 @@
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@c = global i8 42
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@llvm.used = appending global [3 x i8*] [i8* bitcast (void ()* @fa to i8*), i8* bitcast (void ()* @f to i8*), i8* @ca], section "llvm.metadata"
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; CHECK: @llvm.used = appending global [3 x i8*] [i8* bitcast (void ()* @fa to i8*), i8* bitcast (void ()* @f to i8*), i8* @ca], section "llvm.metadata"
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@i = internal global i8 42
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; CHECK: @ia = internal global i8 42
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@ia = alias internal i8* @i
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@llvm.compiler_used = appending global [2 x i8*] [i8* bitcast (void ()* @fa to i8*), i8* bitcast (void ()* @fa3 to i8*)], section "llvm.metadata"
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@llvm.used = appending global [3 x i8*] [i8* bitcast (void ()* @fa to i8*), i8* bitcast (void ()* @f to i8*), i8* @ca], section "llvm.metadata"
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; CHECK-DAG: @llvm.used = appending global [3 x i8*] [i8* bitcast (void ()* @fa to i8*), i8* bitcast (void ()* @f to i8*), i8* @ca], section "llvm.metadata"
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@llvm.compiler_used = appending global [4 x i8*] [i8* bitcast (void ()* @fa3 to i8*), i8* bitcast (void ()* @fa to i8*), i8* @ia, i8* @i], section "llvm.metadata"
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; CHECK-DAG: @llvm.compiler_used = appending global [2 x i8*] [i8* bitcast (void ()* @fa3 to i8*), i8* @ia], section "llvm.metadata"
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@sameAsUsed = global [3 x i8*] [i8* bitcast (void ()* @fa to i8*), i8* bitcast (void ()* @f to i8*), i8* @ca]
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; CHECK: @sameAsUsed = global [3 x i8*] [i8* bitcast (void ()* @f to i8*), i8* bitcast (void ()* @f to i8*), i8* @c]
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; CHECK-DAG: @sameAsUsed = global [3 x i8*] [i8* bitcast (void ()* @f to i8*), i8* bitcast (void ()* @f to i8*), i8* @c]
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@other = global i32* bitcast (void ()* @fa to i32*)
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; CHECK: @other = global i32* bitcast (void ()* @f to i32*)
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; CHECK-DAG: @other = global i32* bitcast (void ()* @f to i32*)
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@fa = alias internal void ()* @f
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; CHECK: @fa = alias internal void ()* @f
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