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release/22.x: [clang] Fix issues with const/pure on varargs function. (#190252) #190405

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Merged
c-rhodes merged 1 commit into from
Apr 6, 2026
Merged

release/22.x: [clang] Fix issues with const/pure on varargs function. (#190252) #190405

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14 changes: 13 additions & 1 deletion clang/lib/CodeGen/CGCall.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3024,6 +3024,11 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
}
assert(ArgNo == FI.arg_size());

// We can't see all potential arguments in a varargs declaration; treat them
// as if they can access memory.
if (!AttrOnCallSite && FI.isVariadic())
AddPotentialArgAccess();

ArgNo = 0;
if (AddedPotentialArgAccess && MemAttrForPtrArgs) {
llvm::FunctionType *FunctionType = getTypes().GetFunctionType(FI);
Expand All @@ -3035,7 +3040,14 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
unsigned FirstIRArg, NumIRArgs;
std::tie(FirstIRArg, NumIRArgs) = IRFunctionArgs.getIRArgs(ArgNo);
for (unsigned i = FirstIRArg; i < FirstIRArg + NumIRArgs; ++i) {
if (FunctionType->getParamType(i)->isPointerTy()) {
// The index may be out-of-bounds if the callee is a varargs
// function.
//
// FIXME: We can compute the types of varargs arguments without going
// through the function type, but the relevant code isn't exposed
// in a way that can be called from here.
if (i < FunctionType->getNumParams() &&
FunctionType->getParamType(i)->isPointerTy()) {
ArgAttrs[i] =
ArgAttrs[i].addAttribute(getLLVMContext(), *MemAttrForPtrArgs);
}
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39 changes: 34 additions & 5 deletions clang/test/CodeGen/struct-passing.c
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Expand Up @@ -18,18 +18,47 @@ int __attribute__((pure)) f5(T1 a);
T1 __attribute__((const)) f6(void*, int);
T1 __attribute__((pure)) f7(void*, int);

void *ps[] = { f0, f1, f2, f3, f4, f5, f6, f7 };
T1 __attribute__((const)) f8(int, ...);
int __attribute__((const)) f9(int, ...);

void *ps[] = { f0, f1, f2, f3, f4, f5, f6, f7, f8, f9 };

// Check markings for varargs arguments.
//
// FIXME: We can add markings in more cases.
void test(T1 t1, void *p) {
f8(1);
f8(1, t1);
f8(1, p);

f9(1);
f9(1, t1);
f9(1, p);
}

// CHECK: declare i32 @f0() [[RN:#[0-9]+]]
// CHECK: declare i32 @f1() [[RO:#[0-9]+]]
// CHECK: declare void @f2(ptr {{[^,]*}} sret({{[^)]*}}) align 4) [[RNRW:#[0-9]+]]
// CHECK: declare void @f3(ptr {{[^,]*}} sret({{[^)]*}}) align 4) [[RORW:#[0-9]+]]
// CHECK: declare i32 @f4(ptr {{[^,]*}} byval({{[^)]*}}) align 4) [[RNRW:#[0-9]+]]
// CHECK: declare i32 @f5(ptr {{[^,]*}} byval({{[^)]*}}) align 4) [[RORW:#[0-9]+]]
// CHECK: declare void @f6(ptr {{[^,]*}} sret({{[^)]*}}) align 4, ptr {{[^,]*}} readnone, i32 {{[^,]*}}) [[RNRW:#[0-9]+]]
// CHECK: declare void @f7(ptr {{[^,]*}} sret({{[^)]*}}) align 4, ptr {{[^,]*}} readonly, i32 {{[^,]*}}) [[RORW:#[0-9]+]]
// CHECK: declare i32 @f4(ptr {{[^,]*}} byval({{[^)]*}}) align 4) [[RNRW]]
// CHECK: declare i32 @f5(ptr {{[^,]*}} byval({{[^)]*}}) align 4) [[RORW]]
// CHECK: declare void @f6(ptr {{[^,]*}} sret({{[^)]*}}) align 4, ptr {{[^,]*}} readnone, i32 {{[^,]*}}) [[RNRW]]
// CHECK: declare void @f7(ptr {{[^,]*}} sret({{[^)]*}}) align 4, ptr {{[^,]*}} readonly, i32 {{[^,]*}}) [[RORW]]
// CHECK: declare void @f8(ptr dead_on_unwind writable sret(%struct.T1) align 4, i32 noundef, ...) [[RNRW]]
// CHECK: declare i32 @f9(i32 noundef, ...) [[RNRW]]


// CHECK: call void (ptr, i32, ...) @f8(ptr dead_on_unwind writable sret(%struct.T1) align 4 {{.*}}, i32 noundef 1) [[RNRW_CALL:#[0-9]+]]
// CHECK: call void (ptr, i32, ...) @f8(ptr dead_on_unwind writable sret(%struct.T1) align 4 {{.*}}, i32 noundef 1, ptr noundef byval(%struct.T1) align 4 {{.*}}) [[RNRW_CALL]]
// CHECK: call void (ptr, i32, ...) @f8(ptr dead_on_unwind writable sret(%struct.T1) align 4 {{.*}}, i32 noundef 1, ptr noundef %0) [[RNRW_CALL]]
// CHECK: call i32 (i32, ...) @f9(i32 noundef 1) [[RN_CALL:#[0-9]+]]
// CHECK: call i32 (i32, ...) @f9(i32 noundef 1, ptr noundef byval(%struct.T1) align 4 {{.*}}) [[RNRW_CALL]]
// CHECK: call i32 (i32, ...) @f9(i32 noundef 1, ptr noundef %1) [[RN_CALL]]


// CHECK: attributes [[RN]] = { nounwind willreturn memory(none){{.*}} }
// CHECK: attributes [[RO]] = { nounwind willreturn memory(read){{.*}} }
// CHECK: attributes [[RNRW]] = { nounwind willreturn memory(argmem: readwrite){{.*}} }
// CHECK: attributes [[RORW]] = { nounwind willreturn memory(read, argmem: readwrite){{.*}} }
// CHECK: attributes [[RNRW_CALL]] = { nounwind willreturn memory(argmem: readwrite) }
// CHECK: attributes [[RN_CALL]] = { nounwind willreturn memory(none) }
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