[llvm] r269731 - Debug Info: Don't emit a DW_AT_data_member_location for DWARF bitfields.

[Adrian Prantl via llvm-commits]

Author: adrian
Date: Mon May 16 21:37:53 2016
New Revision: 269731

URL: http://llvm.org/viewvc/llvm-project?rev=269731&view=rev
Log:
Debug Info: Don't emit a DW_AT_data_member_location for DWARF bitfields.
The DWARF spec states that a member entry may have either a
DW_AT_data_member_location or a DW_AT_data_bit_offset, but not both.

This fixes a bug found in PR 27758.

Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
    llvm/trunk/test/DebugInfo/ARM/big-endian-bitfield.ll
    llvm/trunk/test/DebugInfo/X86/bitfields-dwarf4.ll

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp?rev=269731&r1=269730&r2=269731&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp Mon May 16 21:37:53 2016
@@ -1390,8 +1390,8 @@ void DwarfUnit::constructMemberDIE(DIE &
     uint64_t Size = DT->getSizeInBits();
     uint64_t FieldSize = getBaseTypeSize(DD, DT);
     uint64_t OffsetInBytes;
-
-    if (FieldSize && Size != FieldSize) {
+    bool IsBitfield = FieldSize && Size != FieldSize;
+    if (IsBitfield) {
       // Handle bitfield, assume bytes are 8 bits.
       if (DD->getDwarfVersion() < 4)
         addUInt(MemberDie, dwarf::DW_AT_byte_size, None, FieldSize/8);
@@ -1428,7 +1428,7 @@ void DwarfUnit::constructMemberDIE(DIE &
       addUInt(*MemLocationDie, dwarf::DW_FORM_data1, dwarf::DW_OP_plus_uconst);
       addUInt(*MemLocationDie, dwarf::DW_FORM_udata, OffsetInBytes);
       addBlock(MemberDie, dwarf::DW_AT_data_member_location, MemLocationDie);
-    } else
+    } else if (!IsBitfield || DD->getDwarfVersion() < 4)
       addUInt(MemberDie, dwarf::DW_AT_data_member_location, None,
               OffsetInBytes);
   }

Modified: llvm/trunk/test/DebugInfo/ARM/big-endian-bitfield.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/ARM/big-endian-bitfield.ll?rev=269731&r1=269730&r2=269731&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/ARM/big-endian-bitfield.ll (original)
+++ llvm/trunk/test/DebugInfo/ARM/big-endian-bitfield.ll Mon May 16 21:37:53 2016
@@ -29,26 +29,22 @@ target datalayout = "E-m:e-p:32:32-i64:6
 ; CHECK-NEXT: DW_AT_name{{.*}}"j"
 ; CHECK-NOT:  DW_TAG
 ; CHECK:      DW_AT_data_bit_offset      [DW_FORM_data1]	(0x00)
-; CHECK:      DW_AT_data_member_location [DW_FORM_data1]	(0x00)
 !7 = !DIDerivedType(tag: DW_TAG_member, name: "j", scope: !5, file: !1, line: 2, baseType: !8, size: 5, align: 32)
 !8 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 ; CHECK: DW_TAG_member
 ; CHECK-NEXT: DW_AT_name{{.*}}"k"
 ; CHECK-NOT:  DW_TAG
 ; CHECK:      DW_AT_data_bit_offset      [DW_FORM_data1]	(0x05)
-; CHECK:      DW_AT_data_member_location [DW_FORM_data1]	(0x00)
 !9 = !DIDerivedType(tag: DW_TAG_member, name: "k", scope: !5, file: !1, line: 3, baseType: !8, size: 6, align: 32, offset: 5)
 ; CHECK: DW_TAG_member
 ; CHECK-NEXT: DW_AT_name{{.*}}"m"
 ; CHECK-NOT:  DW_TAG
 ; CHECK:      DW_AT_data_bit_offset      [DW_FORM_data1]	(0x0b)
-; CHECK:      DW_AT_data_member_location [DW_FORM_data1]	(0x00)
 !10 = !DIDerivedType(tag: DW_TAG_member, name: "m", scope: !5, file: !1, line: 4, baseType: !8, size: 5, align: 32, offset: 11)
 ; CHECK: DW_TAG_member
 ; CHECK-NEXT: DW_AT_name{{.*}}"n"
 ; CHECK-NOT:  DW_TAG
 ; CHECK:      DW_AT_data_bit_offset      [DW_FORM_data1]	(0x10)
-; CHECK:      DW_AT_data_member_location [DW_FORM_data1]	(0x00)
 !11 = !DIDerivedType(tag: DW_TAG_member, name: "n", scope: !5, file: !1, line: 5, baseType: !8, size: 8, align: 32, offset: 16)
 !12 = !{i32 2, !"Dwarf Version", i32 4}
 !13 = !{i32 2, !"Debug Info Version", i32 3}

Modified: llvm/trunk/test/DebugInfo/X86/bitfields-dwarf4.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/bitfields-dwarf4.ll?rev=269731&r1=269730&r2=269731&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/bitfields-dwarf4.ll (original)
+++ llvm/trunk/test/DebugInfo/X86/bitfields-dwarf4.ll Mon May 16 21:37:53 2016
@@ -50,7 +50,7 @@ target triple = "x86_64-apple-macosx"
 ; CHECK:      DW_AT_bit_size             [DW_FORM_data1]	(0x05)
 ; CHECK-NOT:  DW_AT_byte_size
 ; CHECK-NEXT: DW_AT_data_bit_offset      [DW_FORM_data1]	(0x08)
-; CHECK-NEXT: DW_AT_data_member_location [DW_FORM_data1]	(0x00)
+; CHECK-NOT:  DW_AT_data_member_location
 !9 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !5, file: !1, line: 6, baseType: !10, size: 5, align: 32, offset: 8)
 
 !10 = !DIDerivedType(tag: DW_TAG_typedef, name: "uint32_t", file: !11, line: 183, baseType: !12)
@@ -64,7 +64,8 @@ target triple = "x86_64-apple-macosx"
 ; CHECK-NOT:  DW_AT_byte_size
 ; CHECK:      DW_AT_bit_size             [DW_FORM_data1]	(0x1b)
 ; CHECK-NEXT: DW_AT_data_bit_offset      [DW_FORM_data1]	(0x0d)
-; CHECK-NEXT: DW_AT_data_member_location [DW_FORM_data1]	(0x00)
+; CHECK-NOT:  DW_AT_data_member_location
+; CHECK: DW_TAG
 !13 = !DIDerivedType(tag: DW_TAG_member, name: "c", scope: !5, file: !1, line: 7, baseType: !10, size: 27, align: 32, offset: 13)
 
 !14 = !{i32 2, !"Dwarf Version", i32 4}