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Revert "[FMV] Emit the resolver along with the default version defini…
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…tion." (#85914)

Reverts #84405

In between of passing the precommit tests on github and being merged
some change (perhaps in the AArch64 backend?) landed which resulted
in altering the generated resolver. I will regenerate the tests
perhaps using a less sensitive runline to such changes.
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@labrinea
labrinea committed Mar 20, 2024
1 parent 0247564 commit b7975ca
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Showing 4 changed files with 238 additions and 629 deletions.
55 changes: 13 additions & 42 deletions clang/lib/CodeGen/CodeGenModule.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3449,9 +3449,6 @@ bool CodeGenModule::MayBeEmittedEagerly(const ValueDecl *Global) {
// Implicit template instantiations may change linkage if they are later
// explicitly instantiated, so they should not be emitted eagerly.
return false;
// Defer until all versions have been semantically checked.
if (FD->hasAttr<TargetVersionAttr>() && !FD->isMultiVersion())
return false;
}
if (const auto *VD = dyn_cast<VarDecl>(Global)) {
if (Context.getInlineVariableDefinitionKind(VD) ==
Expand Down Expand Up @@ -4000,13 +3997,10 @@ void CodeGenModule::EmitMultiVersionFunctionDefinition(GlobalDecl GD,
EmitGlobalFunctionDefinition(GD.getWithMultiVersionIndex(I), nullptr);
// Ensure that the resolver function is also emitted.
GetOrCreateMultiVersionResolver(GD);
} else if (FD->hasAttr<TargetVersionAttr>()) {
GetOrCreateMultiVersionResolver(GD);
} else
EmitGlobalFunctionDefinition(GD, GV);

// Defer the resolver emission until we can reason whether the TU
// contains a default target version implementation.
if (FD->isTargetVersionMultiVersion())
AddDeferredMultiVersionResolverToEmit(GD);
}

void CodeGenModule::EmitGlobalDefinition(GlobalDecl GD, llvm::GlobalValue *GV) {
Expand Down Expand Up @@ -4099,11 +4093,10 @@ void CodeGenModule::emitMultiVersionFunctions() {
const auto *FD = cast<FunctionDecl>(GD.getDecl());
assert(FD && "Expected a FunctionDecl");

bool EmitResolver = !FD->isTargetVersionMultiVersion();
SmallVector<CodeGenFunction::MultiVersionResolverOption, 10> Options;
if (FD->isTargetMultiVersion()) {
getContext().forEachMultiversionedFunctionVersion(
FD, [this, &GD, &Options, &EmitResolver](const FunctionDecl *CurFD) {
FD, [this, &GD, &Options](const FunctionDecl *CurFD) {
GlobalDecl CurGD{
(CurFD->isDefined() ? CurFD->getDefinition() : CurFD)};
StringRef MangledName = getMangledName(CurGD);
Expand All @@ -4129,9 +4122,6 @@ void CodeGenModule::emitMultiVersionFunctions() {
TA->getArchitecture(), Feats);
} else {
const auto *TVA = CurFD->getAttr<TargetVersionAttr>();
if (CurFD->isUsed() || (TVA->isDefaultVersion() &&
CurFD->doesThisDeclarationHaveABody()))
EmitResolver = true;
llvm::SmallVector<StringRef, 8> Feats;
TVA->getFeatures(Feats);
Options.emplace_back(cast<llvm::Function>(Func),
Expand Down Expand Up @@ -4187,27 +4177,22 @@ void CodeGenModule::emitMultiVersionFunctions() {
continue;
}

if (!EmitResolver)
continue;

llvm::Constant *ResolverConstant = GetOrCreateMultiVersionResolver(GD);
if (auto *IFunc = dyn_cast<llvm::GlobalIFunc>(ResolverConstant)) {
ResolverConstant = IFunc->getResolver();
if (FD->isTargetClonesMultiVersion() ||
FD->isTargetVersionMultiVersion()) {
const CGFunctionInfo &FI = getTypes().arrangeGlobalDeclaration(GD);
llvm::FunctionType *DeclTy = getTypes().GetFunctionType(FI);
std::string MangledName = getMangledNameImpl(
*this, GD, FD, /*OmitMultiVersionMangling=*/true);
if (!GetGlobalValue(MangledName + ".ifunc")) {
const CGFunctionInfo &FI = getTypes().arrangeGlobalDeclaration(GD);
llvm::FunctionType *DeclTy = getTypes().GetFunctionType(FI);
// In prior versions of Clang, the mangling for ifuncs incorrectly
// included an .ifunc suffix. This alias is generated for backward
// compatibility. It is deprecated, and may be removed in the future.
auto *Alias = llvm::GlobalAlias::create(
DeclTy, 0, getMultiversionLinkage(*this, GD),
MangledName + ".ifunc", IFunc, &getModule());
SetCommonAttributes(FD, Alias);
}
// In prior versions of Clang, the mangling for ifuncs incorrectly
// included an .ifunc suffix. This alias is generated for backward
// compatibility. It is deprecated, and may be removed in the future.
auto *Alias = llvm::GlobalAlias::create(
DeclTy, 0, getMultiversionLinkage(*this, GD),
MangledName + ".ifunc", IFunc, &getModule());
SetCommonAttributes(FD, Alias);
}
}
llvm::Function *ResolverFunc = cast<llvm::Function>(ResolverConstant);
Expand Down Expand Up @@ -4364,20 +4349,6 @@ void CodeGenModule::emitCPUDispatchDefinition(GlobalDecl GD) {
}
}

/// Adds a declaration to the list of multi version functions if not present.
void CodeGenModule::AddDeferredMultiVersionResolverToEmit(GlobalDecl GD) {
const auto *FD = cast<FunctionDecl>(GD.getDecl());
assert(FD && "Not a FunctionDecl?");

if (FD->isTargetVersionMultiVersion()) {
std::string MangledName =
getMangledNameImpl(*this, GD, FD, /*OmitMultiVersionMangling=*/true);
if (!DeferredResolversToEmit.insert(MangledName).second)
return;
}
MultiVersionFuncs.push_back(GD);
}

/// If a dispatcher for the specified mangled name is not in the module, create
/// and return an llvm Function with the specified type.
llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
Expand Down Expand Up @@ -4417,7 +4388,7 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
// The resolver needs to be created. For target and target_clones, defer
// creation until the end of the TU.
if (FD->isTargetMultiVersion() || FD->isTargetClonesMultiVersion())
AddDeferredMultiVersionResolverToEmit(GD);
MultiVersionFuncs.push_back(GD);

// For cpu_specific, don't create an ifunc yet because we don't know if the
// cpu_dispatch will be emitted in this translation unit.
Expand Down
5 changes: 0 additions & 5 deletions clang/lib/CodeGen/CodeGenModule.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -348,8 +348,6 @@ class CodeGenModule : public CodeGenTypeCache {
/// yet.
llvm::DenseMap<StringRef, GlobalDecl> DeferredDecls;

llvm::StringSet<llvm::BumpPtrAllocator> DeferredResolversToEmit;

/// This is a list of deferred decls which we have seen that *are* actually
/// referenced. These get code generated when the module is done.
std::vector<GlobalDecl> DeferredDeclsToEmit;
Expand Down Expand Up @@ -1590,9 +1588,6 @@ class CodeGenModule : public CodeGenTypeCache {
llvm::AttributeList ExtraAttrs = llvm::AttributeList(),
ForDefinition_t IsForDefinition = NotForDefinition);

// Adds a declaration to the list of multi version functions if not present.
void AddDeferredMultiVersionResolverToEmit(GlobalDecl GD);

// References to multiversion functions are resolved through an implicitly
// defined resolver function. This function is responsible for creating
// the resolver symbol for the provided declaration. The value returned
Expand Down

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