[CodeGen] Create IFUNCs in the program address space, not hard-coded 0

[jrtc27]

Commit 0d527e5 ("GlobalIFunc: Make ifunc respect function address
spaces") added support for this within LLVM, but Clang does not properly
honour the target's address spaces when creating IFUNCs, crashing with
RAUW and verifier assertion failures when compiling C code on a target
with a non-zero program address space, so fix this.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-codegen

Author: Jessica Clarke (jrtc27)

Changes

Commit 0d527e5 ("GlobalIFunc: Make ifunc respect function address
spaces") added support for this within LLVM, but Clang does not properly
honour the target's address spaces when creating IFUNCs, crashing with
RAUW and verifier assertion failures when compiling C code on a target
with a non-zero program address space, so fix this.

---

Full diff: https://github.com/llvm/llvm-project/pull/105726.diff

2 Files Affected:

• (modified) clang/lib/CodeGen/CodeGenModule.cpp (+9-7)
• (modified) clang/test/CodeGen/ifunc.c (+5)

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 6d11bd17d0a5f5..ce681dd878bc7e 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -4443,11 +4443,12 @@ void CodeGenModule::emitCPUDispatchDefinition(GlobalDecl GD) {
   if (getTarget().supportsIFunc()) {
     llvm::GlobalValue::LinkageTypes Linkage = getMultiversionLinkage(*this, GD);
     auto *IFunc = cast<llvm::GlobalValue>(GetOrCreateMultiVersionResolver(GD));
+    unsigned AS = IFunc->getType()->getPointerAddressSpace();
 
     // Fix up function declarations that were created for cpu_specific before
     // cpu_dispatch was known
     if (!isa<llvm::GlobalIFunc>(IFunc)) {
-      auto *GI = llvm::GlobalIFunc::create(DeclTy, 0, Linkage, "", ResolverFunc,
+      auto *GI = llvm::GlobalIFunc::create(DeclTy, AS, Linkage, "", ResolverFunc,
                                            &getModule());
       replaceDeclarationWith(IFunc, GI);
       IFunc = GI;
@@ -4457,8 +4458,8 @@ void CodeGenModule::emitCPUDispatchDefinition(GlobalDecl GD) {
         *this, GD, FD, /*OmitMultiVersionMangling=*/true);
     llvm::Constant *AliasFunc = GetGlobalValue(AliasName);
     if (!AliasFunc) {
-      auto *GA = llvm::GlobalAlias::create(DeclTy, 0, Linkage, AliasName, IFunc,
-                                           &getModule());
+      auto *GA = llvm::GlobalAlias::create(DeclTy, AS, Linkage, AliasName,
+                                           IFunc, &getModule());
       SetCommonAttributes(GD, GA);
     }
   }
@@ -4530,15 +4531,15 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl 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.
   if (getTarget().supportsIFunc() && !FD->isCPUSpecificMultiVersion()) {
+    unsigned AS = getTypes().getTargetAddressSpace(FD->getType());
     llvm::Type *ResolverType = llvm::FunctionType::get(
-        llvm::PointerType::get(DeclTy,
-                               getTypes().getTargetAddressSpace(FD->getType())),
+        llvm::PointerType::get(DeclTy, AS),
         false);
     llvm::Constant *Resolver = GetOrCreateLLVMFunction(
         MangledName + ".resolver", ResolverType, GlobalDecl{},
         /*ForVTable=*/false);
     llvm::GlobalIFunc *GIF =
-        llvm::GlobalIFunc::create(DeclTy, 0, getMultiversionLinkage(*this, GD),
+        llvm::GlobalIFunc::create(DeclTy, AS, getMultiversionLinkage(*this, GD),
                                   "", Resolver, &getModule());
     GIF->setName(ResolverName);
     SetCommonAttributes(FD, GIF);
@@ -6144,8 +6145,9 @@ void CodeGenModule::emitIFuncDefinition(GlobalDecl GD) {
       GetOrCreateLLVMFunction(IFA->getResolver(), VoidTy, {},
                               /*ForVTable=*/false);
   llvm::Type *DeclTy = getTypes().ConvertTypeForMem(D->getType());
+  unsigned AS = getTypes().getTargetAddressSpace(D->getType());
   llvm::GlobalIFunc *GIF =
-      llvm::GlobalIFunc::create(DeclTy, 0, llvm::Function::ExternalLinkage,
+      llvm::GlobalIFunc::create(DeclTy, AS, llvm::Function::ExternalLinkage,
                                 "", Resolver, &getModule());
   if (Entry) {
     if (GIF->getResolver() == Entry) {
diff --git a/clang/test/CodeGen/ifunc.c b/clang/test/CodeGen/ifunc.c
index 58a00ada687cb0..2849246f93dc3b 100644
--- a/clang/test/CodeGen/ifunc.c
+++ b/clang/test/CodeGen/ifunc.c
@@ -11,6 +11,7 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macosx -fsanitize=thread -O2 -emit-llvm -o - %s | FileCheck %s --check-prefix=SAN
 // RUN: %clang_cc1 -triple arm64-apple-macosx -fsanitize=address -O2 -emit-llvm -o - %s | FileCheck %s --check-prefix=SAN
 // RUN: %clang_cc1 -triple x86_64-apple-macosx -fsanitize=address -O2 -emit-llvm -o - %s | FileCheck %s --check-prefix=SAN
+// RUN: %clang_cc1 -triple avr-unknown-unknown -emit-llvm -o - %s | FileCheck %s --check-prefix=AVR
 
 /// The ifunc is emitted before its resolver.
 int foo(int) __attribute__ ((ifunc("foo_ifunc")));
@@ -55,6 +56,10 @@ extern void hoo(int) __attribute__ ((ifunc("hoo_ifunc")));
 // CHECK: @goo = ifunc void (), ptr @goo_ifunc
 // CHECK: @hoo = ifunc void (i32), ptr @hoo_ifunc
 
+// AVR: @foo = ifunc i16 (i16), ptr addrspace(1) @foo_ifunc
+// AVR: @goo = ifunc void (), ptr addrspace(1) @goo_ifunc
+// AVR: @hoo = ifunc void (i16), ptr addrspace(1) @hoo_ifunc
+
 // CHECK: call i32 @foo(i32
 // CHECK: call void @goo()
 

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[jrtc27]

NB: I would appreciate a review from someone outside the CHERI project