Don't try to diagnose the mismatch unless the warning is enabled

No longer perform the field analysis unless the warning is enabled.

For safety i've updated a few of the existing bitfield tests to also run
with this diagnostic enabled just to get a bit more coverage given we're
no longer running this diagnostic code for every test.

Author: ojhunt

clang/lib/Sema/SemaDecl.cpp

@@ -19406,11 +19406,13 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
 
     if (Record && FD->getType().isVolatileQualified())
       Record->setHasVolatileMember(true);
+    bool ReportMSBitfieldStoragePacking = Record && PreviousField &&
+      !Diags.isIgnored(diag::warn_ms_bitfield_mismatched_storage_packing, Record->getLocation());
     auto IsNonDependentBitField = [](const FieldDecl *FD) {
       return FD->isBitField() && !FD->getType()->isDependentType();
     };
 
-    if (Record && PreviousField && IsNonDependentBitField(FD) &&
+    if (ReportMSBitfieldStoragePacking && IsNonDependentBitField(FD) &&
         IsNonDependentBitField(PreviousField)) {
       CharUnits FDStorageSize = Context.getTypeSizeInChars(FD->getType());
       CharUnits PreviousFieldStorageSize =

clang/test/Sema/bitfield-layout.c

@@ -3,6 +3,8 @@
 // RUN: %clang_cc1 %s -fsyntax-only -verify -triple=aarch64-linux-gnu
 // RUN: %clang_cc1 %s -fsyntax-only -verify -triple=x86_64-pc-linux-gnu
 // RUN: %clang_cc1 %s -fsyntax-only -verify -triple=x86_64-scei-ps4
+// RUN: %clang_cc1 %s -fsyntax-only -verify=checkms -triple=i686-apple-darwin9 -Wms-bitfield-compatibility
+
 // expected-no-diagnostics
 #include <stddef.h>
 
@@ -24,12 +26,27 @@ CHECK_ALIGN(struct, a, 1)
 #endif
 
 // Zero-width bit-fields with packed
-struct __attribute__((packed)) a2 { short x : 9; char : 0; int y : 17; };
+struct __attribute__((packed)) a2 {
+  short x : 9; // #a2x
+  char : 0; // #a2anon
+  // checkms-warning@-1 {{bit-field '' of type 'char' has a different storage size than the preceding bit-field (1 vs 2 bytes) and will not be packed under the MS Windows platform ABI}}
+  // checkms-note@#a2x {{preceding bit-field 'x' declared here with type 'short'}}
+  int y : 17;
+  // checkms-warning@-1 {{bit-field 'y' of type 'int' has a different storage size than the preceding bit-field (4 vs 1 bytes) and will not be packed under the MS Windows platform ABI}}
+  // checkms-note@#a2anon {{preceding bit-field '' declared here with type 'char'}}
+};
+
 CHECK_SIZE(struct, a2, 5)
 CHECK_ALIGN(struct, a2, 1)
 
 // Zero-width bit-fields at the end of packed struct
-struct __attribute__((packed)) a3 { short x : 9; int : 0; };
+struct __attribute__((packed)) a3 {
+  short x : 9; // #a3x
+  int : 0;
+  // checkms-warning@-1 {{bit-field '' of type 'int' has a different storage size than the preceding bit-field (4 vs 2 bytes) and will not be packed under the MS Windows platform ABI}}
+  // checkms-note@#a3x {{preceding bit-field 'x' declared here with type 'short'}}
+};
+
 #if defined(__arm__) || defined(__aarch64__)
 CHECK_SIZE(struct, a3, 4)
 CHECK_ALIGN(struct, a3, 4)
@@ -39,7 +56,12 @@ CHECK_ALIGN(struct, a3, 1)
 #endif
 
 // For comparison, non-zero-width bit-fields at the end of packed struct
-struct __attribute__((packed)) a4 { short x : 9; int : 1; };
+struct __attribute__((packed)) a4 {
+  short x : 9; // #a4x
+  int : 1;
+  // checkms-warning@-1 {{bit-field '' of type 'int' has a different storage size than the preceding bit-field (4 vs 2 bytes) and will not be packed under the MS Windows platform ABI}}
+  // checkms-note@#a4x {{preceding bit-field 'x' declared here with type 'short'}}
+};
 CHECK_SIZE(struct, a4, 2)
 CHECK_ALIGN(struct, a4, 1)
 
@@ -165,22 +187,28 @@ CHECK_OFFSET(struct, g4, c, 3);
 #endif
 
 struct g5 {
-  char : 1;
+  char : 1; // #g5
   __attribute__((aligned(1))) int n : 24;
+  // checkms-warning@-1 {{bit-field 'n' of type 'int' has a different storage size than the preceding bit-field (4 vs 1 bytes) and will not be packed under the MS Windows platform ABI}}
+  // checkms-note@#g5 {{preceding bit-field '' declared here with type 'char'}}
 };
 CHECK_SIZE(struct, g5, 4);
 CHECK_ALIGN(struct, g5, 4);
 
 struct __attribute__((packed)) g6 {
-  char : 1;
+  char : 1; // #g6
   __attribute__((aligned(1))) int n : 24;
+  // checkms-warning@-1 {{bit-field 'n' of type 'int' has a different storage size than the preceding bit-field (4 vs 1 bytes) and will not be packed under the MS Windows platform ABI}}
+  // checkms-note@#g6 {{preceding bit-field '' declared here with type 'char'}}
 };
 CHECK_SIZE(struct, g6, 4);
 CHECK_ALIGN(struct, g6, 1);
 
 struct g7 {
-  char : 1;
+  char : 1; // #g7
   __attribute__((aligned(1))) int n : 25;
+  // checkms-warning@-1 {{bit-field 'n' of type 'int' has a different storage size than the preceding bit-field (4 vs 1 bytes) and will not be packed under the MS Windows platform ABI}}
+  // checkms-note@#g7 {{preceding bit-field '' declared here with type 'char'}}
 };
 #if defined(__ORBIS__)
 CHECK_SIZE(struct, g7, 4);
@@ -190,8 +218,10 @@ CHECK_SIZE(struct, g7, 8);
 CHECK_ALIGN(struct, g7, 4);
 
 struct __attribute__((packed)) g8 {
-  char : 1;
+  char : 1; // #g8
   __attribute__((aligned(1))) int n : 25;
+  // checkms-warning@-1 {{bit-field 'n' of type 'int' has a different storage size than the preceding bit-field (4 vs 1 bytes) and will not be packed under the MS Windows platform ABI}}
+  // checkms-note@#g8 {{preceding bit-field '' declared here with type 'char'}}
 };
 #if defined(__ORBIS__)
 CHECK_SIZE(struct, g8, 4);

clang/test/Sema/bitfield-layout_1.c

@@ -2,6 +2,7 @@
 // RUN: %clang_cc1 %s -fsyntax-only -verify -triple=arm-linux-gnueabihf
 // RUN: %clang_cc1 %s -fsyntax-only -verify -triple=aarch64-linux-gnu
 // RUN: %clang_cc1 %s -fsyntax-only -verify -triple=x86_64-pc-linux-gnu
+// RUN: %clang_cc1 %s -fsyntax-only -verify -triple=i686-apple-darwin9  -Wms-bitfield-compatibility 
 // expected-no-diagnostics
 
 #define CHECK_SIZE(name, size) \

clang/test/Sema/mms-bitfields.c

@@ -1,12 +1,16 @@
 // RUN: %clang_cc1 -mms-bitfields -fsyntax-only -verify -triple x86_64-apple-darwin9 %s
+// RUN: %clang_cc1 -mms-bitfields -fsyntax-only -Wms-bitfield-compatibility -verify=checkms -triple x86_64-apple-darwin9 %s
+
 // expected-no-diagnostics
 
 // The -mms-bitfields commandline parameter should behave the same
 // as the ms_struct attribute.
 struct
 {
-   int a : 1;
+   int a : 1; // #a
    short b : 1;
+   // checkms-warning@-1 {{bit-field 'b' of type 'short' has a different storage size than the preceding bit-field (2 vs 4 bytes) and will not be packed under the MS Windows platform ABI}}
+   // checkms-note@#a {{preceding bit-field 'a' declared here with type 'int'}}
 } t;
 
 // MS pads out bitfields between different types.

clang/test/SemaCXX/bitfield.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 %s -verify
+// RUN: %clang_cc1 %s -verify -Wms-bitfield-compatibility 
 
 // expected-no-diagnostics