Basic support for -mms-bitfields, from Carl Norum!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@124661 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 24 insertions, 0 deletions

diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp
index 7e15dcce37..730ec21358 100644
--- a/lib/AST/RecordLayoutBuilder.cpp
+++ b/lib/AST/RecordLayoutBuilder.cpp
@@ -1402,6 +1402,20 @@ void RecordLayoutBuilder::LayoutField(const FieldDecl *D) {
     std::pair<uint64_t, unsigned> 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.
+      QualType T = Context.getBaseElementType(D->getType());
+      if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
+        uint64_t TypeSize = Context.getTypeSize(BTy);
+        if (TypeSize > FieldAlign)
+          FieldAlign = TypeSize;
+      }
+    }
   }
 
   // The align if the field is not packed. This is to check if the attribute
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index d11db7ed2d..8f8c64d460 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1028,6 +1028,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // work around a linker bug;  see <rdar://problem/7651567>.
   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
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 3fdbc1683c..9ad41458b8 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -583,6 +583,8 @@ static void LangOptsToArgs(const LangOptions &Opts,
     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)
@@ -1445,6 +1447,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
                                                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);
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 7e7bd253af..1e07e76314 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -96,6 +96,7 @@ PCHValidator::ReadLanguageOptions(const LangOptions &LangOpts) {
   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_IMPORTANT(MSBitfields, diag::warn_pch_ms_bitfields);
   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);
@@ -2613,6 +2614,7 @@ bool ASTReader::ParseLanguageOptions(
     PARSE_LANGOPT(AltiVec);
     PARSE_LANGOPT(Exceptions);
     PARSE_LANGOPT(SjLjExceptions);
+    PARSE_LANGOPT(MSBitfields);
     PARSE_LANGOPT(NeXTRuntime);
     PARSE_LANGOPT(Freestanding);
     PARSE_LANGOPT(NoBuiltin);
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index e90640711f..b85aac1cc9 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -911,6 +911,7 @@ void ASTWriter::WriteLanguageOptions(const LangOptions &LangOpts) {
   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)