erichkeane updated this revision to Diff 418682.
erichkeane marked an inline comment as done.
erichkeane added a comment.
Do the two comment fixups aaron suggested.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D122608/new/
https://reviews.llvm.org/D122608
Files:
clang/lib/CodeGen/CodeGenModule.cpp
clang/test/CodeGenCXX/externc-ifunc-resolver.cpp
clang/test/SemaCXX/externc-ifunc-resolver.cpp
Index: clang/test/SemaCXX/externc-ifunc-resolver.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/externc-ifunc-resolver.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -emit-llvm-only -verify %s
+
+extern "C" {
+ __attribute__((used)) static void *resolve_foo() { return 0; }
+ namespace NS {
+ __attribute__((used)) static void *resolve_foo() { return 0; }
+ }
+ __attribute__((ifunc("resolve_foo"))) void foo(); // expected-error{{ifunc must point to a defined function}}
+}
+
Index: clang/test/CodeGenCXX/externc-ifunc-resolver.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/externc-ifunc-resolver.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -o - %s | FileCheck %s
+
+extern "C" {
+ __attribute__((used)) static void *resolve_foo() { return 0; }
+ __attribute__((ifunc("resolve_foo"))) void foo();
+}
+
+// CHECK: @resolve_foo = internal alias i8* (), i8* ()* @_ZL11resolve_foov
+// CHECK: @foo = ifunc void (), bitcast (i8* ()* @_ZL11resolve_foov to void ()* ()*)
+// CHECK: define internal noundef i8* @_ZL11resolve_foov()
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -507,7 +507,6 @@
EmitVTablesOpportunistically();
applyGlobalValReplacements();
applyReplacements();
- checkAliases();
emitMultiVersionFunctions();
EmitCXXGlobalInitFunc();
EmitCXXGlobalCleanUpFunc();
@@ -539,6 +538,7 @@
EmitCtorList(GlobalDtors, "llvm.global_dtors");
EmitGlobalAnnotations();
EmitStaticExternCAliases();
+ checkAliases();
EmitDeferredUnusedCoverageMappings();
CodeGenPGO(*this).setValueProfilingFlag(getModule());
if (CoverageMapping)
@@ -6315,6 +6315,27 @@
GlobalMetadata->addOperand(llvm::MDNode::get(CGM.getLLVMContext(), Ops));
}
+/// If all uses of the GV are from an IFunc resolver, which can happen when the
+/// IFunc resolver is a static-function, but the name ends up being different,
+/// return the IFunc so it can have its resolver replaced with the correct
+/// 'alias' from EmitStaticExternCAliases.
+static llvm::GlobalIFunc *getIFuncFromResolver(llvm::GlobalValue *GV) {
+ // If there is more than 1 use, I don't really know what we can do.
+ // EmitStaticExternCAliases won't be able to do anything, and the ifunc
+ // diagnostic will have to catch this.
+ if (!GV || std::distance(GV->use_begin(), GV->use_end()) != 1)
+ return nullptr;
+
+ llvm::User *U = GV->use_begin()->getUser();
+ if (auto *IFunc = dyn_cast_or_null<llvm::GlobalIFunc>(U)) {
+ assert(IFunc->getResolver() == GV && "Didn't find the resolver use?");
+ assert(GV->isDeclaration() && isa<llvm::Function>(GV) &&
+ "Resolver is defined or not a function?");
+ return IFunc;
+ }
+ return nullptr;
+}
+
/// For each function which is declared within an extern "C" region and marked
/// as 'used', but has internal linkage, create an alias from the unmangled
/// name to the mangled name if possible. People expect to be able to refer
@@ -6326,8 +6347,35 @@
for (auto &I : StaticExternCValues) {
IdentifierInfo *Name = I.first;
llvm::GlobalValue *Val = I.second;
- if (Val && !getModule().getNamedValue(Name->getName()))
- addCompilerUsedGlobal(llvm::GlobalAlias::create(Name->getName(), Val));
+ llvm::GlobalValue *ExistingElem =
+ getModule().getNamedValue(Name->getName());
+ llvm::GlobalIFunc *IFunc = getIFuncFromResolver(ExistingElem);
+
+ if (Val && (!ExistingElem || IFunc)) {
+ // If the IFunc refers to this existing element we have to delete it
+ // FIRST, otherwise the 'name' of the new element will be wrong.
+ llvm::Type *ResolverTy = nullptr;
+ if (IFunc) {
+ ResolverTy = IFunc->getResolverFunction()->getFunctionType();
+ IFunc->setResolver(nullptr);
+ assert(ExistingElem && "Got IFunc without an existing element?");
+ ExistingElem->eraseFromParent();
+ }
+
+ auto *Alias = llvm::GlobalAlias::create(Name->getName(), Val);
+ addCompilerUsedGlobal(Alias);
+
+ // Make sure we 'fix up' the IFunc's resolver. Despite it having been the
+ // 'right' name, we have to make sure we reassign the resolver to the
+ // original static function, since IFuncs aren't allowed to refer to the
+ // alias directly. So, we have to de-alias it here. We have to make sure
+ // the correct bitcasts happen, so we have to re-look up the function.
+ if (IFunc) {
+ llvm::Constant *Resolver = GetOrCreateLLVMFunction(
+ Val->getName(), ResolverTy, {}, /*ForVTable*/ false);
+ IFunc->setResolver(Resolver);
+ }
+ }
}
}
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