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[clang] Add missing readonly/readnone annotations #158424

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Merged
merged 1 commit into from
Sep 23, 2025
Merged

[clang] Add missing readonly/readnone annotations #158424

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26 changes: 26 additions & 0 deletions clang/lib/CodeGen/CGCall.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2438,7 +2438,10 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,

// Some ABIs may result in additional accesses to arguments that may
// otherwise not be present.
std::optional<llvm::Attribute::AttrKind> MemAttrForPtrArgs;
bool AddedPotentialArgAccess = false;
auto AddPotentialArgAccess = [&]() {
AddedPotentialArgAccess = true;
llvm::Attribute A = FuncAttrs.getAttribute(llvm::Attribute::Memory);
if (A.isValid())
FuncAttrs.addMemoryAttr(A.getMemoryEffects() |
Expand Down Expand Up @@ -2499,11 +2502,13 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
// gcc specifies that 'const' functions have greater restrictions than
// 'pure' functions, so they also cannot have infinite loops.
FuncAttrs.addAttribute(llvm::Attribute::WillReturn);
MemAttrForPtrArgs = llvm::Attribute::ReadNone;
} else if (TargetDecl->hasAttr<PureAttr>()) {
FuncAttrs.addMemoryAttr(llvm::MemoryEffects::readOnly());
FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
// gcc specifies that 'pure' functions cannot have infinite loops.
FuncAttrs.addAttribute(llvm::Attribute::WillReturn);
MemAttrForPtrArgs = llvm::Attribute::ReadOnly;
} else if (TargetDecl->hasAttr<NoAliasAttr>()) {
FuncAttrs.addMemoryAttr(llvm::MemoryEffects::inaccessibleOrArgMemOnly());
FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
Expand Down Expand Up @@ -3011,6 +3016,27 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
}
assert(ArgNo == FI.arg_size());

ArgNo = 0;
if (AddedPotentialArgAccess && MemAttrForPtrArgs) {
llvm::FunctionType *FunctionType = FunctionType =
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@mikaelholmen mikaelholmen Oct 7, 2025

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Hi @qchateau

gcc warns on the extra FunctionType = here that I suppose should be removed:

../llvm-project/clang/lib/CodeGen/CGCall.cpp:3021:53: warning: operation on 'FunctionType' may be undefined [-Wsequence-point]
 3021 |     llvm::FunctionType *FunctionType = FunctionType =
      |                                        ~~~~~~~~~~~~~^
 3022 |         getTypes().GetFunctionType(FI);
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

getTypes().GetFunctionType(FI);
for (CGFunctionInfo::const_arg_iterator I = FI.arg_begin(),
E = FI.arg_end();
I != E; ++I, ++ArgNo) {
if (I->info.isDirect() || I->info.isExpand() ||
I->info.isCoerceAndExpand()) {
unsigned FirstIRArg, NumIRArgs;
std::tie(FirstIRArg, NumIRArgs) = IRFunctionArgs.getIRArgs(ArgNo);
for (unsigned i = FirstIRArg; i < FirstIRArg + NumIRArgs; ++i) {
if (FunctionType->getParamType(i)->isPointerTy()) {
ArgAttrs[i] =
ArgAttrs[i].addAttribute(getLLVMContext(), *MemAttrForPtrArgs);
}
}
}
}
}

AttrList = llvm::AttributeList::get(
getLLVMContext(), llvm::AttributeSet::get(getLLVMContext(), FuncAttrs),
llvm::AttributeSet::get(getLLVMContext(), RetAttrs), ArgAttrs);
Expand Down
22 changes: 15 additions & 7 deletions clang/test/CodeGen/struct-passing.c
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Expand Up @@ -11,17 +11,25 @@ T0 __attribute__((const)) f0(void);
T0 __attribute__((pure)) f1(void);
T1 __attribute__((const)) f2(void);
T1 __attribute__((pure)) f3(void);
void __attribute__((const)) f4(T1 a);
void __attribute__((pure)) f5(T1 a);
int __attribute__((const)) f4(T1 a);
int __attribute__((pure)) f5(T1 a);

void *ps[] = { f0, f1, f2, f3, f4, f5 };
// NOTE: The int parameters verifies non-ptr parameters are not a problem
T1 __attribute__((const)) f6(void*, int);
T1 __attribute__((pure)) f7(void*, int);

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

// CHECK: declare i32 @f0() [[RN:#[0-9]+]]
// CHECK: declare i32 @f1() [[RO:#[0-9]+]]
// CHECK: declare void @f2({{.*}} sret({{.*}}) align 4)
// CHECK: declare void @f3({{.*}} sret({{.*}}) align 4)
// CHECK: declare void @f4({{.*}} byval({{.*}}) align 4)
// CHECK: declare void @f5({{.*}} byval({{.*}}) align 4)
// 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: 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){{.*}} }