https://github.com/DanShaders updated
https://github.com/llvm/llvm-project/pull/71148
>From 19124226ee4d08a8025f1e6b61d750096e13ee75 Mon Sep 17 00:00:00 2001
From: Dan Klishch <danilklis...@gmail.com>
Date: Fri, 3 Nov 2023 21:18:06 -0400
Subject: [PATCH] [clang] Stub out gcc_struct attribute
This commit implements gcc_struct attribute with the behavior similar to
one in GCC. Current behavior is as follows:
When C++ ABI is not "Microsoft" (i. e. when
ItaniumRecordLayoutBuilder is used), [[gcc_struct]] will locally cancel
the effect of -mms-bitfields on a record. If -mms-bitfields is not
supplied and is not a default behavior on a target, [[gcc_struct]] will
be a no-op. This should provide enough compatibility with GCC.
If C++ ABI is "Microsoft", [[gcc_struct]] will currently always be a
no-op, since support for it is not yet implemented in
MicrosoftRecordLayoutBuilder. Note, however, that all the infrastructure
is ready for the future implementation.
In particular, check for default value of -mms-bitfield is moved from a
driver to TargetInfo, since it now non-trivially depends on other
supplied flags. Also, unfortunately, this makes it impossible to use
usual argument parsing for `-m{no-,}ms-bitfield`.
The patch doesn't introduce any not backwards-compatible changes, except
for situations when cc1 is called directly on a target with
-mms-bitfields being a default option.
---
clang/include/clang/Basic/Attr.td | 7 +++++
clang/include/clang/Basic/LangOptions.def | 1 -
clang/include/clang/Basic/LangOptions.h | 2 ++
clang/include/clang/Basic/TargetInfo.h | 4 +++
clang/include/clang/Driver/Options.td | 4 +--
clang/lib/AST/Decl.cpp | 7 ++++-
clang/lib/CodeGen/CGRecordLayoutBuilder.cpp | 5 +---
clang/lib/Driver/ToolChains/Clang.cpp | 10 ++++---
clang/lib/Frontend/CompilerInvocation.cpp | 12 +++++++++
clang/lib/Sema/SemaDecl.cpp | 4 +--
clang/lib/Sema/SemaDeclCXX.cpp | 27 ++++++++++++-------
clang/test/Driver/ms-bitfields.c | 11 +++++---
clang/test/Layout/itanium-union-bitfield.cpp | 2 +-
...a-attribute-supported-attributes-list.test | 1 +
14 files changed, 69 insertions(+), 28 deletions(-)
diff --git a/clang/include/clang/Basic/Attr.td
b/clang/include/clang/Basic/Attr.td
index 60b549999c155e5..34ec6c22481837e 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -3635,6 +3635,13 @@ def MSStruct : InheritableAttr {
let SimpleHandler = 1;
}
+def GCCStruct : InheritableAttr {
+ let Spellings = [GCC<"gcc_struct">];
+ let Subjects = SubjectList<[Record]>;
+ let Documentation = [Undocumented];
+ let SimpleHandler = 1;
+}
+
def DLLExport : InheritableAttr, TargetSpecificAttr<TargetHasDLLImportExport> {
let Spellings = [Declspec<"dllexport">, GCC<"dllexport">];
let Subjects = SubjectList<[Function, Var, CXXRecord, ObjCInterface]>;
diff --git a/clang/include/clang/Basic/LangOptions.def
b/clang/include/clang/Basic/LangOptions.def
index c0ea4ecb9806a5b..afbb3c724a8d193 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -148,7 +148,6 @@ LANGOPT(ExternCNoUnwind , 1, 0, "Assume extern C
functions don't unwind")
LANGOPT(TraditionalCPP , 1, 0, "traditional CPP emulation")
LANGOPT(RTTI , 1, 1, "run-time type information")
LANGOPT(RTTIData , 1, 1, "emit run-time type information data")
-LANGOPT(MSBitfields , 1, 0, "Microsoft-compatible structure layout")
LANGOPT(MSVolatile , 1, 0, "Microsoft-compatible volatile loads and
stores")
LANGOPT(Freestanding, 1, 0, "freestanding implementation")
LANGOPT(NoBuiltin , 1, 0, "disable builtin functions")
diff --git a/clang/include/clang/Basic/LangOptions.h
b/clang/include/clang/Basic/LangOptions.h
index 20a8ada60e0fe51..07eae8dad61813c 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -502,6 +502,8 @@ class LangOptions : public LangOptionsBase {
// received as a result of a standard operator new (-fcheck-new)
bool CheckNew = false;
+ std::optional<bool> MSBitfields;
+
LangOptions();
/// Set language defaults for the given input language and
diff --git a/clang/include/clang/Basic/TargetInfo.h
b/clang/include/clang/Basic/TargetInfo.h
index b3c5cbfb319f01f..6865b6e23bc9628 100644
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -1724,6 +1724,10 @@ class TargetInfo : public TransferrableTargetInfo,
/// Whether to support HIP image/texture API's.
virtual bool hasHIPImageSupport() const { return true; }
+ virtual bool defaultsToMsStruct() const {
+ return getCXXABI().isMicrosoft() || getTriple().isWindowsGNUEnvironment();
+ }
+
protected:
/// Copy type and layout related info.
void copyAuxTarget(const TargetInfo *Aux);
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index 9c0dcaa8b3f6276..d29214ed3cb13db 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4381,8 +4381,7 @@ def : Joined<["-"], "mmacosx-version-min=">,
Group<m_Group>, Alias<mmacos_version_min_EQ>;
def mms_bitfields : Flag<["-"], "mms-bitfields">, Group<m_Group>,
Visibility<[ClangOption, CC1Option]>,
- HelpText<"Set the default structure layout to be compatible with the
Microsoft compiler standard">,
- MarshallingInfoFlag<LangOpts<"MSBitfields">>;
+ HelpText<"Set the default structure layout to be compatible with the
Microsoft compiler standard">;
def moutline : Flag<["-"], "moutline">, Group<f_clang_Group>,
Visibility<[ClangOption, CC1Option]>,
HelpText<"Enable function outlining (AArch64 only)">;
@@ -4390,6 +4389,7 @@ def mno_outline : Flag<["-"], "mno-outline">,
Group<f_clang_Group>,
Visibility<[ClangOption, CC1Option]>,
HelpText<"Disable function outlining (AArch64 only)">;
def mno_ms_bitfields : Flag<["-"], "mno-ms-bitfields">, Group<m_Group>,
+ Visibility<[ClangOption, CC1Option]>,
HelpText<"Do not set the default structure layout to be compatible with the
Microsoft compiler standard">;
def mskip_rax_setup : Flag<["-"], "mskip-rax-setup">, Group<m_Group>,
Visibility<[ClangOption, CC1Option]>,
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index ed848e574233468..a0817fab9f7dcf8 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -5031,7 +5031,12 @@ void RecordDecl::completeDefinition() {
/// This which can be turned on with an attribute, pragma, or the
/// -mms-bitfields command-line option.
bool RecordDecl::isMsStruct(const ASTContext &C) const {
- return hasAttr<MSStructAttr>() || C.getLangOpts().MSBitfields == 1;
+ if (hasAttr<MSStructAttr>())
+ return true;
+ if (hasAttr<GCCStructAttr>())
+ return false;
+ return C.getLangOpts().MSBitfields.value_or(
+ C.getTargetInfo().defaultsToMsStruct());
}
void RecordDecl::reorderDecls(const SmallVectorImpl<Decl *> &Decls) {
diff --git a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
index cbfa79e10bfefcc..296151c32c91c12 100644
--- a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
+++ b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
@@ -104,10 +104,7 @@ struct CGRecordLowering {
/// fields of the same formal type. We want to emit a layout with
/// these discrete storage units instead of combining them into a
/// continuous run.
- bool isDiscreteBitFieldABI() {
- return Context.getTargetInfo().getCXXABI().isMicrosoft() ||
- D->isMsStruct(Context);
- }
+ bool isDiscreteBitFieldABI() { return D->isMsStruct(Context); }
/// Helper function to check if we are targeting AAPCS.
bool isAAPCS() const {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp
b/clang/lib/Driver/ToolChains/Clang.cpp
index 79f7fba22570746..2602d1f6bedee9f 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5645,9 +5645,13 @@ void Clang::ConstructJob(Compilation &C, const JobAction
&JA,
if (KernelOrKext && RawTriple.isOSDarwin())
CmdArgs.push_back("-fforbid-guard-variables");
- if (Args.hasFlag(options::OPT_mms_bitfields, options::OPT_mno_ms_bitfields,
- Triple.isWindowsGNUEnvironment())) {
- CmdArgs.push_back("-mms-bitfields");
+ if (Args.hasArg(options::OPT_mms_bitfields) ||
+ Args.hasArg(options::OPT_mno_ms_bitfields)) {
+ if (Args.hasFlag(options::OPT_mms_bitfields, options::OPT_mno_ms_bitfields,
+ false))
+ CmdArgs.push_back("-mms-bitfields");
+ else
+ CmdArgs.push_back("-mno-ms-bitfields");
}
if (Triple.isWindowsGNUEnvironment()) {
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp
b/clang/lib/Frontend/CompilerInvocation.cpp
index 637c6a35af6532b..a0576441c5d24a7 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3619,6 +3619,13 @@ void CompilerInvocationBase::GenerateLangArgs(const
LangOptions &Opts,
GenerateArg(Consumer, OPT_fcxx_abi_EQ,
TargetCXXABI::getSpelling(*Opts.CXXABI));
+ if (Opts.MSBitfields.has_value()) {
+ if (Opts.MSBitfields.value())
+ GenerateArg(Consumer, OPT_mms_bitfields);
+ else
+ GenerateArg(Consumer, OPT_mno_ms_bitfields);
+ }
+
if (Opts.RelativeCXXABIVTables)
GenerateArg(Consumer, OPT_fexperimental_relative_cxx_abi_vtables);
else
@@ -4153,6 +4160,11 @@ bool CompilerInvocation::ParseLangArgs(LangOptions
&Opts, ArgList &Args,
options::OPT_fno_experimental_relative_cxx_abi_vtables,
TargetCXXABI::usesRelativeVTables(T));
+ if (Args.hasArg(options::OPT_mms_bitfields) ||
+ Args.hasArg(options::OPT_mno_ms_bitfields))
+ Opts.MSBitfields = Args.hasFlag(options::OPT_mms_bitfields,
+ options::OPT_mno_ms_bitfields, false);
+
// RTTI is on by default.
bool HasRTTI = Args.hasFlag(options::OPT_frtti, options::OPT_fno_rtti, true);
Opts.OmitVTableRTTI =
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 396566a8f10a9b7..27fb20eb8181b62 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -18199,9 +18199,7 @@ ExprResult Sema::VerifyBitField(SourceLocation FieldLoc,
// ABI.
bool CStdConstraintViolation =
BitfieldIsOverwide && !getLangOpts().CPlusPlus;
- bool MSBitfieldViolation =
- Value.ugt(TypeStorageSize) &&
- (IsMsStruct || Context.getTargetInfo().getCXXABI().isMicrosoft());
+ bool MSBitfieldViolation = Value.ugt(TypeStorageSize) && IsMsStruct;
if (CStdConstraintViolation || MSBitfieldViolation) {
unsigned DiagWidth =
CStdConstraintViolation ? TypeWidth : TypeStorageSize;
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 397b7a00e453126..09e5768deefdc57 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -7255,20 +7255,27 @@ void Sema::CheckCompletedCXXClass(Scope *S,
CXXRecordDecl *Record) {
CheckCompletedMemberFunction(MD);
}
- // ms_struct is a request to use the same ABI rules as MSVC. Check
- // whether this class uses any C++ features that are implemented
- // completely differently in MSVC, and if so, emit a diagnostic.
- // That diagnostic defaults to an error, but we allow projects to
- // map it down to a warning (or ignore it). It's a fairly common
- // practice among users of the ms_struct pragma to mass-annotate
- // headers, sweeping up a bunch of types that the project doesn't
- // really rely on MSVC-compatible layout for. We must therefore
- // support "ms_struct except for C++ stuff" as a secondary ABI.
+ // {ms,gcc}_struct is a request to change ABI rules to either follow
+ // Microsoft or Itanium C++ ABI. However, even if these attributes are
+ // present, we do not layout classes following foreign ABI rules, but
+ // instead enter a special "compatibility mode", which only changes
+ // alignements of fundamental types and layout of bit fields.
+ // Check whether this class uses any C++ features that are implemented
+ // completely differently in the requested ABI, and if so, emit a
+ // diagnostic. That diagnostic defaults to an error, but we allow
+ // projects to map it down to a warning (or ignore it). It's a fairly
+ // common practice among users of the ms_struct pragma to
+ // mass-annotate headers, sweeping up a bunch of types that the
+ // project doesn't really rely on MSVC-compatible layout for. We must
+ // therefore support "ms_struct except for C++ stuff" as a secondary
+ // ABI.
// Don't emit this diagnostic if the feature was enabled as a
// language option (as opposed to via a pragma or attribute), as
// the option -mms-bitfields otherwise essentially makes it impossible
// to build C++ code, unless this diagnostic is turned off.
- if (Record->isMsStruct(Context) && !Context.getLangOpts().MSBitfields &&
+ if (!Context.getLangOpts().MSBitfields.has_value() &&
+ Record->isMsStruct(Context) !=
+ Context.getTargetInfo().defaultsToMsStruct() &&
(Record->isPolymorphic() || Record->getNumBases())) {
Diag(Record->getLocation(), diag::warn_cxx_ms_struct);
}
diff --git a/clang/test/Driver/ms-bitfields.c b/clang/test/Driver/ms-bitfields.c
index 031ed41e2aad678..4cd3f1380e41acf 100644
--- a/clang/test/Driver/ms-bitfields.c
+++ b/clang/test/Driver/ms-bitfields.c
@@ -1,8 +1,13 @@
-// RUN: %clang -### -target x86_64-linux-gnu %s 2>&1 | FileCheck %s
-check-prefix=NO-MSBITFIELDS
-// RUN: %clang -### -target x86_64-windows-gnu %s 2>&1 | FileCheck %s
-check-prefix=MSBITFIELDS
+// RUN: %clang -### -target x86_64-linux-gnu %s 2>&1 | FileCheck %s
-check-prefix=DEFAULT-MSBITFIELDS
+// RUN: %clang -### -target x86_64-windows-gnu %s 2>&1 | FileCheck %s
-check-prefix=DEFAULT-MSBITFIELDS
+// RUN: %clang -### -target x86_64-windows-msvc %s 2>&1 | FileCheck %s
-check-prefix=DEFAULT-MSBITFIELDS
+// RUN: %clang -### -mms-bitfields %s 2>&1 | FileCheck %s
-check-prefix=MSBITFIELDS
+// RUN: %clang -### -mno-ms-bitfields %s 2>&1 | FileCheck %s
-check-prefix=NO-MSBITFIELDS
// RUN: %clang -### -mno-ms-bitfields -mms-bitfields %s 2>&1 | FileCheck %s
-check-prefix=MSBITFIELDS
// RUN: %clang -### -mms-bitfields -mno-ms-bitfields %s 2>&1 | FileCheck %s
-check-prefix=NO-MSBITFIELDS
// MSBITFIELDS: -mms-bitfields
-// NO-MSBITFIELDS-NOT: -mms-bitfields
+// NO-MSBITFIELDS: -mno-ms-bitfields
+// DEFAULT-MSBITFIELDS-NOT: -mms-bitfields
+// DEFAULT-MSBITFIELDS-NOT: -mno-ms-bitfields
diff --git a/clang/test/Layout/itanium-union-bitfield.cpp
b/clang/test/Layout/itanium-union-bitfield.cpp
index febfc46dfee54c1..3e22fe9a3faabd3 100644
--- a/clang/test/Layout/itanium-union-bitfield.cpp
+++ b/clang/test/Layout/itanium-union-bitfield.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -emit-llvm-only -triple %itanium_abi_triple
-fdump-record-layouts %s 2>/dev/null \
+// RUN: %clang_cc1 -emit-llvm-only -triple %itanium_abi_triple
-mno-ms-bitfields -fdump-record-layouts %s 2>/dev/null \
// RUN: | FileCheck %s
// On z/OS, a bit-field has single byte alignment. Add aligned(4) on z/OS so
the union has
diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
index f48126775c8685c..eb237f7ebb1b2e8 100644
--- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -73,6 +73,7 @@
// CHECK-NEXT: FlagEnum (SubjectMatchRule_enum)
// CHECK-NEXT: Flatten (SubjectMatchRule_function)
// CHECK-NEXT: FunctionReturnThunks (SubjectMatchRule_function)
+// CHECK-NEXT: GCCStruct (SubjectMatchRule_record)
// CHECK-NEXT: GNUInline (SubjectMatchRule_function)
// CHECK-NEXT: HIPManaged (SubjectMatchRule_variable)
// CHECK-NEXT: Hot (SubjectMatchRule_function)
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