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[MS] Apply `inreg` to AArch64 sret parms on instance methods 

The documentation rules indicate that instance methods should return
large, trivially copyable aggregates via X1/X0 and not X8 as is normally
done when returning such structs from free functions:
https://docs.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=vs-2019#return-values

Fixes PR47836, a bug in the initial implementation of these rules.

I tried to simplify the logic a bit as well while I'm here.

Differential Revision: https://reviews.llvm.org/D89362
This commit is contained in:
Reid Kleckner 2020-10-13 19:58:39 -07:00
parent 6754caa9bf
commit 5fbab4025e
2 changed files with 42 additions and 22 deletions
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48
clang/lib/CodeGen/MicrosoftCXXABI.cpp
View File

@ -1070,11 +1070,7 @@ bool MicrosoftCXXABI::hasMostDerivedReturn(GlobalDecl GD) const {
return isDeletingDtor(GD);
}
static bool IsSizeGreaterThan128(const CXXRecordDecl *RD) {
return RD->getASTContext().getTypeSize(RD->getTypeForDecl()) > 128;
}
static bool hasMicrosoftABIRestrictions(const CXXRecordDecl *RD) {
static bool isCXX14Aggregate(const CXXRecordDecl *RD) {
// For AArch64, we use the C++14 definition of an aggregate, so we also
// check for:
// No private or protected non static data members.
@ -1083,19 +1079,19 @@ static bool hasMicrosoftABIRestrictions(const CXXRecordDecl *RD) {
// Additionally, we need to ensure that there is a trivial copy assignment
// operator, a trivial destructor and no user-provided constructors.
if (RD->hasProtectedFields() || RD->hasPrivateFields())
return true;
return false;
if (RD->getNumBases() > 0)
return true;
return false;
if (RD->isPolymorphic())
return true;
return false;
if (RD->hasNonTrivialCopyAssignment())
return true;
return false;
for (const CXXConstructorDecl *Ctor : RD->ctors())
if (Ctor->isUserProvided())
return true;
return false;
if (RD->hasNonTrivialDestructor())
return true;
return false;
return false;
return true;
}
bool MicrosoftCXXABI::classifyReturnType(CGFunctionInfo &FI) const {
@ -1103,21 +1099,29 @@ bool MicrosoftCXXABI::classifyReturnType(CGFunctionInfo &FI) const {
if (!RD)
return false;
// Normally, the C++ concept of "is trivially copyable" is used to determine
// if a struct can be returned directly. However, as MSVC and the language
// have evolved, the definition of "trivially copyable" has changed, while the
// ABI must remain stable. AArch64 uses the C++14 concept of an "aggregate",
// while other ISAs use the older concept of "plain old data".
bool isTrivialForABI = RD->isPOD();
bool isAArch64 = CGM.getTarget().getTriple().isAArch64();
bool isSimple = !isAArch64 || !hasMicrosoftABIRestrictions(RD);
bool isIndirectReturn =
isAArch64 ? (!RD->canPassInRegisters() ||
IsSizeGreaterThan128(RD))
: !RD->isPOD();
bool isInstanceMethod = FI.isInstanceMethod();
if (isAArch64)
isTrivialForABI = RD->canPassInRegisters() && isCXX14Aggregate(RD);
if (isIndirectReturn || !isSimple || isInstanceMethod) {
// MSVC always returns structs indirectly from C++ instance methods.
bool isIndirectReturn = !isTrivialForABI || FI.isInstanceMethod();
if (isIndirectReturn) {
CharUnits Align = CGM.getContext().getTypeAlignInChars(FI.getReturnType());
FI.getReturnInfo() = ABIArgInfo::getIndirect(Align, /*ByVal=*/false);
FI.getReturnInfo().setSRetAfterThis(isInstanceMethod);
FI.getReturnInfo().setInReg(isAArch64 &&
!(isSimple && IsSizeGreaterThan128(RD)));
// MSVC always passes `this` before the `sret` parameter.
FI.getReturnInfo().setSRetAfterThis(FI.isInstanceMethod());
// On AArch64, use the `inreg` attribute if the object is considered to not
// be trivially copyable, or if this is an instance method struct return.
FI.getReturnInfo().setInReg(isAArch64);
return true;
}

16
clang/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
View File

@ -87,17 +87,20 @@ Small small_return() { return Small(); }
// LINUX-LABEL: define void @_Z12small_returnv(%struct.Small* noalias sret align 4 %agg.result)
// WIN32: define dso_local i32 @"?small_return@@YA?AUSmall@@XZ"()
// WIN64: define dso_local i32 @"?small_return@@YA?AUSmall@@XZ"()
// WOA64: define dso_local i64 @"?small_return@@YA?AUSmall@@XZ"()
Medium medium_return() { return Medium(); }
// LINUX-LABEL: define void @_Z13medium_returnv(%struct.Medium* noalias sret align 4 %agg.result)
// WIN32: define dso_local i64 @"?medium_return@@YA?AUMedium@@XZ"()
// WIN64: define dso_local i64 @"?medium_return@@YA?AUMedium@@XZ"()
// WOA64: define dso_local i64 @"?medium_return@@YA?AUMedium@@XZ"()
// Returning structs that fit into a register but are not POD.
SmallCpp11NotCpp03Pod small_non_pod_return() { return SmallCpp11NotCpp03Pod(); }
// LINUX-LABEL: define void @_Z20small_non_pod_returnv(%struct.SmallCpp11NotCpp03Pod* noalias sret align 4 %agg.result)
// WIN32: define dso_local void @"?small_non_pod_return@@YA?AUSmallCpp11NotCpp03Pod@@XZ"(%struct.SmallCpp11NotCpp03Pod* noalias sret align 4 %agg.result)
// WIN64: define dso_local void @"?small_non_pod_return@@YA?AUSmallCpp11NotCpp03Pod@@XZ"(%struct.SmallCpp11NotCpp03Pod* noalias sret align 4 %agg.result)
// WOA64: define dso_local void @"?small_non_pod_return@@YA?AUSmallCpp11NotCpp03Pod@@XZ"(%struct.SmallCpp11NotCpp03Pod* inreg noalias sret align 4 %agg.result)
SmallWithCtor small_with_ctor_return() { return SmallWithCtor(); }
// LINUX-LABEL: define void @_Z22small_with_ctor_returnv(%struct.SmallWithCtor* noalias sret align 4 %agg.result)
@ -106,23 +109,33 @@ SmallWithCtor small_with_ctor_return() { return SmallWithCtor(); }
// FIXME: The 'sret' mark here doesn't seem to be enough to convince LLVM to
// preserve the hidden sret pointer in R0 across the function.
// WOA: define dso_local arm_aapcs_vfpcc void @"?small_with_ctor_return@@YA?AUSmallWithCtor@@XZ"(%struct.SmallWithCtor* noalias sret align 4 %agg.result)
// WOA64: define dso_local void @"?small_with_ctor_return@@YA?AUSmallWithCtor@@XZ"(%struct.SmallWithCtor* inreg noalias sret align 4 %agg.result)
SmallWithDtor small_with_dtor_return() { return SmallWithDtor(); }
// LINUX-LABEL: define void @_Z22small_with_dtor_returnv(%struct.SmallWithDtor* noalias sret align 4 %agg.result)
// WIN32: define dso_local void @"?small_with_dtor_return@@YA?AUSmallWithDtor@@XZ"(%struct.SmallWithDtor* noalias sret align 4 %agg.result)
// WIN64: define dso_local void @"?small_with_dtor_return@@YA?AUSmallWithDtor@@XZ"(%struct.SmallWithDtor* noalias sret align 4 %agg.result)
// WOA64: define dso_local void @"?small_with_dtor_return@@YA?AUSmallWithDtor@@XZ"(%struct.SmallWithDtor* inreg noalias sret align 4 %agg.result)
SmallWithVftable small_with_vftable_return() { return SmallWithVftable(); }
// LINUX-LABEL: define void @_Z25small_with_vftable_returnv(%struct.SmallWithVftable* noalias sret align 4 %agg.result)
// WIN32: define dso_local void @"?small_with_vftable_return@@YA?AUSmallWithVftable@@XZ"(%struct.SmallWithVftable* noalias sret align 4 %agg.result)
// WIN64: define dso_local void @"?small_with_vftable_return@@YA?AUSmallWithVftable@@XZ"(%struct.SmallWithVftable* noalias sret align 8 %agg.result)
// WOA64: define dso_local void @"?small_with_vftable_return@@YA?AUSmallWithVftable@@XZ"(%struct.SmallWithVftable* inreg noalias sret align 8 %agg.result)
MediumWithCopyCtor medium_with_copy_ctor_return() { return MediumWithCopyCtor(); }
// LINUX-LABEL: define void @_Z28medium_with_copy_ctor_returnv(%struct.MediumWithCopyCtor* noalias sret align 4 %agg.result)
// WIN32: define dso_local void @"?medium_with_copy_ctor_return@@YA?AUMediumWithCopyCtor@@XZ"(%struct.MediumWithCopyCtor* noalias sret align 4 %agg.result)
// WIN64: define dso_local void @"?medium_with_copy_ctor_return@@YA?AUMediumWithCopyCtor@@XZ"(%struct.MediumWithCopyCtor* noalias sret align 4 %agg.result)
// WOA: define dso_local arm_aapcs_vfpcc void @"?medium_with_copy_ctor_return@@YA?AUMediumWithCopyCtor@@XZ"(%struct.MediumWithCopyCtor* noalias sret align 4 %agg.result)
// WOA64: define dso_local void @"?medium_with_copy_ctor_return@@YA?AUMediumWithCopyCtor@@XZ"(%struct.MediumWithCopyCtor* inreg noalias sret align 4 %agg.result)
// Returning a large struct that doesn't fit into a register.
Big big_return() { return Big(); }
// LINUX-LABEL: define void @_Z10big_returnv(%struct.Big* noalias sret align 4 %agg.result)
// WIN32: define dso_local void @"?big_return@@YA?AUBig@@XZ"(%struct.Big* noalias sret align 4 %agg.result)
// WIN64: define dso_local void @"?big_return@@YA?AUBig@@XZ"(%struct.Big* noalias sret align 4 %agg.result)
// WOA64: define dso_local void @"?big_return@@YA?AUBig@@XZ"(%struct.Big* noalias sret align 4 %agg.result)
void small_arg(Small s) {}
@ -284,11 +297,13 @@ class Class {
// LINUX: define {{.*}} void @_ZN5Class21thiscall_method_smallEv(%struct.Small* noalias sret align 4 %agg.result, %class.Class* %this)
// WIN32: define {{.*}} x86_thiscallcc void @"?thiscall_method_small@Class@@QAE?AUSmall@@XZ"(%class.Class* %this, %struct.Small* noalias sret align 4 %agg.result)
// WIN64: define linkonce_odr dso_local void @"?thiscall_method_small@Class@@QEAA?AUSmall@@XZ"(%class.Class* %this, %struct.Small* noalias sret align 4 %agg.result)
// WOA64: define linkonce_odr dso_local void @"?thiscall_method_small@Class@@QEAA?AUSmall@@XZ"(%class.Class* %this, %struct.Small* inreg noalias sret align 4 %agg.result)
SmallWithCtor thiscall_method_small_with_ctor() { return SmallWithCtor(); }
// LINUX: define {{.*}} void @_ZN5Class31thiscall_method_small_with_ctorEv(%struct.SmallWithCtor* noalias sret align 4 %agg.result, %class.Class* %this)
// WIN32: define {{.*}} x86_thiscallcc void @"?thiscall_method_small_with_ctor@Class@@QAE?AUSmallWithCtor@@XZ"(%class.Class* %this, %struct.SmallWithCtor* noalias sret align 4 %agg.result)
// WIN64: define linkonce_odr dso_local void @"?thiscall_method_small_with_ctor@Class@@QEAA?AUSmallWithCtor@@XZ"(%class.Class* %this, %struct.SmallWithCtor* noalias sret align 4 %agg.result)
// WOA64: define linkonce_odr dso_local void @"?thiscall_method_small_with_ctor@Class@@QEAA?AUSmallWithCtor@@XZ"(%class.Class* %this, %struct.SmallWithCtor* inreg noalias sret align 4 %agg.result)
Small __cdecl cdecl_method_small() { return Small(); }
// LINUX: define {{.*}} void @_ZN5Class18cdecl_method_smallEv(%struct.Small* noalias sret align 4 %agg.result, %class.Class* %this)
@ -299,6 +314,7 @@ class Class {
// LINUX: define {{.*}} void @_ZN5Class16cdecl_method_bigEv(%struct.Big* noalias sret align 4 %agg.result, %class.Class* %this)
// WIN32: define {{.*}} void @"?cdecl_method_big@Class@@QAA?AUBig@@XZ"(%class.Class* %this, %struct.Big* noalias sret align 4 %agg.result)
// WIN64: define linkonce_odr dso_local void @"?cdecl_method_big@Class@@QEAA?AUBig@@XZ"(%class.Class* %this, %struct.Big* noalias sret align 4 %agg.result)
// WOA64: define linkonce_odr dso_local void @"?cdecl_method_big@Class@@QEAA?AUBig@@XZ"(%class.Class* %this, %struct.Big* inreg noalias sret align 4 %agg.result)
void thiscall_method_arg(Empty s) {}
// LINUX: define {{.*}} void @_ZN5Class19thiscall_method_argE5Empty(%class.Class* %this)