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Implement DW_TAG_subrange_type with DW_AT_count rather than DW_AT_upper_bound

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This allows proper disambiguation of unbounded arrays and arrays of zero
bound ("struct foo { int x[]; };" and "struct foo { int x[0]; }"). GCC
instead produces an upper bound of -1 in the latter situation, but count
seems tidier. This way lower_bound is provided if it's not the language
default and count is provided if the count is known, otherwise it's
omitted. Simple.

If someone wants to look at rdar://problem/12566646 and see if this
change is acceptable to that bug/fix, that might be helpful (see the
empty-and-one-elem-array.ll test case which cites that radar).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218726 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Blaikie 2014-10-01 00:56:55 +00:00
parent d0d5b08fbd
commit 06c1373053
4 changed files with 8 additions and 14 deletions
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9
lib/CodeGen/AsmPrinter/DwarfUnit.cpp
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@ -1748,9 +1748,7 @@ void DwarfUnit::constructSubrangeDIE(DIE &Buffer, DISubrange SR, DIE *IndexTy) {
// The LowerBound value defines the lower bounds which is typically zero for
// C/C++. The Count value is the number of elements. Values are 64 bit. If
// Count == -1 then the array is unbounded and we do not emit
// DW_AT_lower_bound and DW_AT_upper_bound attributes. If LowerBound == 0 and
// Count == 0, then the array has zero elements in which case we do not emit
// an upper bound.
// DW_AT_lower_bound and DW_AT_count attributes.
int64_t LowerBound = SR.getLo();
int64_t DefaultLowerBound = getDefaultLowerBound();
int64_t Count = SR.getCount();
@ -1758,11 +1756,10 @@ void DwarfUnit::constructSubrangeDIE(DIE &Buffer, DISubrange SR, DIE *IndexTy) {
if (DefaultLowerBound == -1 || LowerBound != DefaultLowerBound)
addUInt(DW_Subrange, dwarf::DW_AT_lower_bound, None, LowerBound);
if (Count != -1 && Count != 0)
if (Count != -1)
// FIXME: An unbounded array should reference the expression that defines
// the array.
addUInt(DW_Subrange, dwarf::DW_AT_upper_bound, None,
LowerBound + Count - 1);
addUInt(DW_Subrange, dwarf::DW_AT_count, None, Count);
}
/// constructArrayTypeDIE - Construct array type DIE from DICompositeType.

2
test/DebugInfo/X86/dbg-subrange.ll
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@ -4,7 +4,7 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
target triple = "x86_64-apple-macosx10.7.2"
@s = common global [4294967296 x i8] zeroinitializer, align 16
;CHECK: .long 4294967295
; CHECK: .quad 4294967296 ## DW_AT_count
define void @bar() nounwind uwtable ssp {
entry:

9
test/DebugInfo/X86/empty-and-one-elem-array.ll
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@ -25,9 +25,6 @@ entry:
declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
; An empty array should not have an AT_upper_bound attribute. But an array of 1
; should.
; CHECK: DW_TAG_base_type
; CHECK-NEXT: DW_AT_name [DW_FORM_strp] ( .debug_str[{{.*}}] = "int")
; CHECK-NEXT: DW_AT_encoding [DW_FORM_data1] (DW_ATE_signed)
@ -46,7 +43,7 @@ declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
; CHECK-NEXT: DW_AT_type [DW_FORM_ref4]
; CHECK: DW_TAG_subrange_type [{{.*}}]
; CHECK-NEXT: DW_AT_type [DW_FORM_ref4]
; CHECK-NEXT: DW_AT_upper_bound [DW_FORM_data1] (0x00)
; CHECK-NEXT: DW_AT_count [DW_FORM_data1] (0x01)
; int bar::b[0]:
; CHECK: DW_TAG_structure_type
@ -59,9 +56,9 @@ declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
; int[0]:
; CHECK: DW_TAG_array_type [{{.*}}] *
; CHECK-NEXT: DW_AT_type [DW_FORM_ref4]
; CHECK: DW_TAG_subrange_type [11]
; CHECK: DW_TAG_subrange_type
; CHECK-NEXT: DW_AT_type [DW_FORM_ref4]
; CHECK-NOT: DW_AT_upper_bound
; CHECK: DW_AT_count [DW_FORM_data1] (0x00)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!33}

2
test/DebugInfo/X86/nondefault-subrange-array.ll
View File

@ -19,7 +19,7 @@
; CHECK: DW_TAG_subrange_type
; CHECK-NEXT: DW_AT_type [DW_FORM_ref4] (cu + 0x{{[0-9a-f]*}} => {[[BASE2:0x[0-9a-f]*]]})
; CHECK-NEXT: DW_AT_lower_bound [DW_FORM_data8] (0xfffffffffffffffd)
; CHECK-NEXT: DW_AT_upper_bound [DW_FORM_data1] (0x26)
; CHECK-NEXT: DW_AT_count [DW_FORM_data1] (0x2a)
; CHECK: [[BASE]]: DW_TAG_base_type
; CHECK: [[BASE2]]: DW_TAG_base_type