Do not honor explicit alignment attribute on fields for PS4.

This change reverts r257462 for PS4 triple.

Differential Revision: http://reviews.llvm.org/D16788

llvm-svn: 259916

clang/include/clang/Basic/TargetInfo.h

@@ -202,6 +202,9 @@ protected:
   /// zero-length bitfield.
   unsigned UseZeroLengthBitfieldAlignment : 1;
 
+  /// \brief  Whether explicit bit field alignment attributes are honored.
+  unsigned UseExplicitBitFieldAlignment : 1;
+
   /// If non-zero, specifies a fixed alignment value for bitfields that follow
   /// zero length bitfield, regardless of the zero length bitfield type.
   unsigned ZeroLengthBitfieldBoundary;
@@ -466,6 +469,12 @@ public:
     return ZeroLengthBitfieldBoundary;
   }
 
+  /// \brief Check whether explicit bitfield alignment attributes should be
+  //  honored, as in "__attribute__((aligned(2))) int b : 1;".
+  bool useExplicitBitFieldAlignment() const {
+    return UseExplicitBitFieldAlignment;
+  }
+
   /// \brief Check whether this target support '\#pragma options align=mac68k'.
   bool hasAlignMac68kSupport() const {
     return HasAlignMac68kSupport;

clang/lib/AST/RecordLayoutBuilder.cpp

@@ -1600,7 +1600,8 @@ void ItaniumRecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
         (AllowPadding &&
          (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize)) {
       FieldOffset = llvm::alignTo(FieldOffset, FieldAlign);
-    } else if (ExplicitFieldAlign) {
+    } else if (ExplicitFieldAlign &&
+               Context.getTargetInfo().useExplicitBitFieldAlignment()) {
       // TODO: figure it out what needs to be done on targets that don't honor
       // bit-field type alignment like ARM APCS ABI.
       FieldOffset = llvm::alignTo(FieldOffset, ExplicitFieldAlign);
@@ -1612,7 +1613,8 @@ void ItaniumRecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
          (UnpackedFieldOffset & (UnpackedFieldAlign-1)) + FieldSize > TypeSize))
       UnpackedFieldOffset =
           llvm::alignTo(UnpackedFieldOffset, UnpackedFieldAlign);
-    else if (ExplicitFieldAlign)
+    else if (ExplicitFieldAlign &&
+             Context.getTargetInfo().useExplicitBitFieldAlignment())
       UnpackedFieldOffset =
           llvm::alignTo(UnpackedFieldOffset, ExplicitFieldAlign);
   }

clang/lib/Basic/TargetInfo.cpp

@@ -66,6 +66,7 @@ TargetInfo::TargetInfo(const llvm::Triple &T) : TargetOpts(), Triple(T) {
   UseSignedCharForObjCBool = true;
   UseBitFieldTypeAlignment = true;
   UseZeroLengthBitfieldAlignment = false;
+  UseExplicitBitFieldAlignment = true;
   ZeroLengthBitfieldBoundary = 0;
   HalfFormat = &llvm::APFloat::IEEEhalf;
   FloatFormat = &llvm::APFloat::IEEEsingle;

clang/lib/Basic/Targets.cpp

@@ -606,6 +606,10 @@ public:
     this->MaxTLSAlign = 256;
     this->UserLabelPrefix = "";
 
+    // On PS4, do not honor explicit bit field alignment,
+    // as in "__attribute__((aligned(2))) int b : 1;".
+    this->UseExplicitBitFieldAlignment = false;
+
     switch (Triple.getArch()) {
     default:
     case llvm::Triple::x86_64:

clang/test/Sema/bitfield-layout.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=x86_64-scei-ps4
 // expected-no-diagnostics
 #include <stddef.h>
 
@@ -96,9 +97,15 @@ struct g0 {
   char c;
 };
 
+#if defined(__PS4__)
+CHECK_SIZE(struct, g0, 16);
+CHECK_ALIGN(struct, g0, 16);
+CHECK_OFFSET(struct, g0, c, 2);
+#else
 CHECK_SIZE(struct, g0, 32);
 CHECK_ALIGN(struct, g0, 16);
 CHECK_OFFSET(struct, g0, c, 17);
+#endif
 
 // Bit-field with explicit align smaller than normal.
 struct g1 {
@@ -109,7 +116,11 @@ struct g1 {
 
 CHECK_SIZE(struct, g1, 4);
 CHECK_ALIGN(struct, g1, 4);
+#if defined(__PS4__)
+CHECK_OFFSET(struct, g1, c, 2);
+#else
 CHECK_OFFSET(struct, g1, c, 3);
+#endif
 
 // Same as above but without explicit align.
 struct g2 {
@@ -130,9 +141,14 @@ struct __attribute__((packed)) g3 {
   char c;
 };
 
-CHECK_SIZE(struct, g3, 32);
 CHECK_ALIGN(struct, g3, 16);
+#if defined(__PS4__)
+CHECK_SIZE(struct, g3, 16);
+CHECK_OFFSET(struct, g3, c, 2);
+#else
+CHECK_SIZE(struct, g3, 32);
 CHECK_OFFSET(struct, g3, c, 17);
+#endif
 
 struct __attribute__((packed)) g4 {
   char a;
@@ -142,7 +158,11 @@ struct __attribute__((packed)) g4 {
 
 CHECK_SIZE(struct, g4, 4);
 CHECK_ALIGN(struct, g4, 2);
+#if defined(__PS4__)
+CHECK_OFFSET(struct, g4, c, 2);
+#else
 CHECK_OFFSET(struct, g4, c, 3);
+#endif
 
 struct g5 {
   char : 1;
@@ -162,28 +182,44 @@ struct g7 {
   char : 1;
   __attribute__((aligned(1))) int n : 25;
 };
+#if defined(__PS4__)
+CHECK_SIZE(struct, g7, 4);
+#else
 CHECK_SIZE(struct, g7, 8);
+#endif
 CHECK_ALIGN(struct, g7, 4);
 
 struct __attribute__((packed)) g8 {
   char : 1;
   __attribute__((aligned(1))) int n : 25;
 };
+#if defined(__PS4__)
+CHECK_SIZE(struct, g8, 4);
+#else
 CHECK_SIZE(struct, g8, 5);
+#endif
 CHECK_ALIGN(struct, g8, 1);
 
 struct g9 {
   __attribute__((aligned(1))) char a : 2, b : 2, c : 2, d : 2, e : 2;
   int i;
 };
+#if defined(__PS4__)
+CHECK_SIZE(struct, g9, 8);
+#else
 CHECK_SIZE(struct, g9, 12);
+#endif
 CHECK_ALIGN(struct, g9, 4);
 
 struct __attribute__((packed)) g10 {
   __attribute__((aligned(1))) char a : 2, b : 2, c : 2, d : 2, e : 2;
   int i;
 };
+#if defined(__PS4__)
+CHECK_SIZE(struct, g10, 6);
+#else
 CHECK_SIZE(struct, g10, 9);
+#endif
 CHECK_ALIGN(struct, g10, 1);
 
 struct g11 {