Index: test/Misc/mms-bitfields.c =================================================================== --- test/Misc/mms-bitfields.c (revision 0) +++ test/Misc/mms-bitfields.c (revision 0) @@ -0,0 +1,22 @@ +// RUN: %clang_cc1 -triple i386-apple-darwin10 -mms-bitfields -emit-llvm %s -o - | FileCheck %s + +struct s1 { + int f32; + long long f64; +} s1; + +// CHECK: %struct.s1 = type { i32, [4 x i8], i64 } + +struct s2 { + int f32; + long long f64[4]; +} s2; + +// CHECK: %struct.s2 = type { i32, [4 x i8], [4 x i64] } + +struct s3 { + int f32; + struct s1 s; +} s3; + +// CHECK: %struct.s3 = type { i32, [4 x i8], %struct.s1 } Index: include/clang/Basic/LangOptions.h =================================================================== --- include/clang/Basic/LangOptions.h (revision 124313) +++ include/clang/Basic/LangOptions.h (working copy) @@ -56,6 +56,7 @@ unsigned SjLjExceptions : 1; // Use setjmp-longjump exception handling. unsigned RTTI : 1; // Support RTTI information. + unsigned MSBitfields : 1; // MS-compatible structure layout unsigned NeXTRuntime : 1; // Use NeXT runtime. unsigned Freestanding : 1; // Freestanding implementation unsigned NoBuiltin : 1; // Do not use builtin functions (-fno-builtin) @@ -163,6 +164,7 @@ C99 = Microsoft = Borland = CPlusPlus = CPlusPlus0x = 0; CXXOperatorNames = PascalStrings = WritableStrings = ConstStrings = 0; Exceptions = SjLjExceptions = Freestanding = NoBuiltin = 0; + MSBitfields = 0; NeXTRuntime = 1; RTTI = 1; LaxVectorConversions = 1; Index: include/clang/Driver/CC1Options.td =================================================================== --- include/clang/Driver/CC1Options.td (revision 124313) +++ include/clang/Driver/CC1Options.td (working copy) @@ -183,6 +183,8 @@ HelpText<"Generate unwinding tables for all functions">; def mconstructor_aliases : Flag<"-mconstructor-aliases">, HelpText<"Emit complete constructors and destructors as aliases when possible">; +def mms_bitfields : Flag<"-mms-bitfields">, + HelpText<"Set the default structure layout to be compatible with the Microsoft compiler standard.">; def O : Joined<"-O">, HelpText<"Optimization level">; def Os : Flag<"-Os">, HelpText<"Optimize for size">; Index: include/clang/Driver/Options.td =================================================================== --- include/clang/Driver/Options.td (revision 124313) +++ include/clang/Driver/Options.td (working copy) @@ -476,6 +476,7 @@ def mlinker_version_EQ : Joined<"-mlinker-version=">, Flags<[NoForward]>; def mllvm : Separate<"-mllvm">; def mmacosx_version_min_EQ : Joined<"-mmacosx-version-min=">, Group; +def mms_bitfields : Flag<"-mms-bitfields">, Group; def mmmx : Flag<"-mmmx">, Group; def mno_3dnowa : Flag<"-mno-3dnowa">, Group; def mno_3dnow : Flag<"-mno-3dnow">, Group; Index: lib/Frontend/CompilerInvocation.cpp =================================================================== --- lib/Frontend/CompilerInvocation.cpp (revision 124313) +++ lib/Frontend/CompilerInvocation.cpp (working copy) @@ -579,6 +579,8 @@ Res.push_back("-fsjlj-exceptions"); if (!Opts.RTTI) Res.push_back("-fno-rtti"); + if (Opts.MSBitfields) + Res.push_back("-mms-bitfields"); if (!Opts.NeXTRuntime) Res.push_back("-fgnu-runtime"); if (Opts.Freestanding) @@ -1433,6 +1435,7 @@ Diags); Opts.NumLargeByValueCopy = Args.getLastArgIntValue(OPT_Wlarge_by_value_copy, 0, Diags); + Opts.MSBitfields = Args.hasArg(OPT_mms_bitfields); Opts.NeXTRuntime = !Args.hasArg(OPT_fgnu_runtime); Opts.ObjCConstantStringClass = Args.getLastArgValue(OPT_fconstant_string_class); Index: lib/AST/RecordLayoutBuilder.cpp =================================================================== --- lib/AST/RecordLayoutBuilder.cpp (revision 124313) +++ lib/AST/RecordLayoutBuilder.cpp (working copy) @@ -1401,6 +1401,33 @@ std::pair FieldInfo = Context.getTypeInfo(D->getType()); FieldSize = FieldInfo.first; FieldAlign = FieldInfo.second; + + if (Context.getLangOptions().MSBitfields) { + // If MS bitfield layout is required, figure out what type is being + // laid out and align the field to the width of that type. + + // Resolve all typedefs down to their base type and round up the field + // alignment if necessary. + const BuiltinType *BTy = D->getType()->getAs(); + if (BTy != NULL) { + if (FieldSize > FieldAlign) { + FieldAlign = FieldSize; + } + } + + // Check for array type + const ArrayType *ATy = Context.getAsArrayType(D->getType()); + if (ATy != NULL) { + QualType ElementType = ATy->getElementType(); + BTy = ElementType->getAs(); + if (BTy != NULL) { + uint64_t ElementSize = Context.getTypeSize(ElementType); + if (ElementSize > FieldAlign) { + FieldAlign = ElementSize; + } + } + } + } } // The align if the field is not packed. This is to check if the attribute Index: lib/Driver/Tools.cpp =================================================================== --- lib/Driver/Tools.cpp (revision 124313) +++ lib/Driver/Tools.cpp (working copy) @@ -1028,6 +1028,10 @@ // work around a linker bug; see . if (getToolChain().getTriple().getOS() != llvm::Triple::Darwin) CmdArgs.push_back("-mconstructor-aliases"); + + if (Args.hasArg(options::OPT_mms_bitfields)) { + CmdArgs.push_back("-mms-bitfields"); + } // This is a coarse approximation of what llvm-gcc actually does, both // -fasynchronous-unwind-tables and -fnon-call-exceptions interact in more Index: lib/Serialization/ASTWriter.cpp =================================================================== --- lib/Serialization/ASTWriter.cpp (revision 124313) +++ lib/Serialization/ASTWriter.cpp (working copy) @@ -911,6 +911,7 @@ Record.push_back(LangOpts.Exceptions); // Support exception handling. Record.push_back(LangOpts.SjLjExceptions); + Record.push_back(LangOpts.MSBitfields); // MS-compatible structure layout Record.push_back(LangOpts.NeXTRuntime); // Use NeXT runtime. Record.push_back(LangOpts.Freestanding); // Freestanding implementation Record.push_back(LangOpts.NoBuiltin); // Do not use builtin functions (-fno-builtin) Index: lib/Serialization/ASTReader.cpp =================================================================== --- lib/Serialization/ASTReader.cpp (revision 124313) +++ lib/Serialization/ASTReader.cpp (working copy) @@ -96,6 +96,7 @@ PARSE_LANGOPT_IMPORTANT(AltiVec, diag::warn_pch_altivec); PARSE_LANGOPT_IMPORTANT(Exceptions, diag::warn_pch_exceptions); PARSE_LANGOPT_IMPORTANT(SjLjExceptions, diag::warn_pch_sjlj_exceptions); + PARSE_LANGOPT_BENIGN(MSBitfields); PARSE_LANGOPT_IMPORTANT(NeXTRuntime, diag::warn_pch_objc_runtime); PARSE_LANGOPT_IMPORTANT(Freestanding, diag::warn_pch_freestanding); PARSE_LANGOPT_IMPORTANT(NoBuiltin, diag::warn_pch_builtins); @@ -2610,6 +2611,7 @@ PARSE_LANGOPT(AltiVec); PARSE_LANGOPT(Exceptions); PARSE_LANGOPT(SjLjExceptions); + PARSE_LANGOPT(MSBitfields); PARSE_LANGOPT(NeXTRuntime); PARSE_LANGOPT(Freestanding); PARSE_LANGOPT(NoBuiltin);