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PR19767: DebugInfo emission of pointer constants.

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In refactoring DwarfUnit::isUnsignedDIType I restricted it to only work
on values with signedness (unsigned or signed), asserting on anything
else (which did uncover some bugs). But it turns out that we do need to
emit constants of signless data, such as pointer constants - only null
pointer constants are known to need this so far, but it's conceivable
that there might be non-null pointer constants at some point (hardcoded
address offsets for device drivers?).

This patch just uses 'unsigned' for signless data such as pointer
constants. Arguably we could use signless representations
(DW_FORM_dataN) instead, allowing a trinary result from isUnsignedDIType
(signed, unsigned, signless), but this seems reasonable for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209223 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Blaikie 2014-05-20 18:21:51 +00:00
parent 5d7afdb2ec
commit e2ab467b90
2 changed files with 64 additions and 2 deletions
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15
lib/CodeGen/AsmPrinter/DwarfUnit.cpp
View File

@ -749,8 +749,19 @@ void DwarfUnit::addBlockByrefAddress(const DbgVariable &DV, DIE &Die,
static bool isUnsignedDIType(DwarfDebug *DD, DIType Ty) {
DIDerivedType DTy(Ty);
if (DTy.isDerivedType()) {
if (DIType Deriv = DD->resolve(DTy.getTypeDerivedFrom()))
return isUnsignedDIType(DD, Deriv);
dwarf::Tag T = (dwarf::Tag)Ty.getTag();
// Encode pointer constants as unsigned bytes. This is used at least for
// null pointer constant emission. Maybe DW_TAG_reference_type should be
// accepted here too, if there are ways to produce compile-time constant
// references.
if (T == dwarf::DW_TAG_pointer_type ||
T == dwarf::DW_TAG_ptr_to_member_type)
return true;
assert(T == dwarf::DW_TAG_typedef || T == dwarf::DW_TAG_const_type ||
T == dwarf::DW_TAG_volatile_type ||
T == dwarf::DW_TAG_restrict_type);
if (DITypeRef Deriv = DTy.getTypeDerivedFrom())
return isUnsignedDIType(DD, DD->resolve(Deriv));
// FIXME: Enums without a fixed underlying type have unknown signedness
// here, leading to incorrectly emitted constants.
assert(DTy.getTag() == dwarf::DW_TAG_enumeration_type);

51
test/DebugInfo/constant-pointers.ll Normal file
View File

@ -0,0 +1,51 @@
; REQUIRES: object-emission
; RUN: %llc_dwarf -O0 -filetype=obj %s -o - | llvm-dwarfdump -debug-dump=info - | FileCheck %s
; Ensure that pointer constants are emitted as unsigned data. Alternatively,
; these could be signless data (dataN).
; Built with Clang from:
; template <void *V, void (*F)(), int i>
; void func() {}
; template void func<nullptr, nullptr, 42>();
; CHECK: DW_TAG_subprogram
; CHECK: DW_TAG_template_value_parameter
; CHECK: DW_AT_name {{.*}} "V"
; CHECK: DW_AT_const_value [DW_FORM_udata] (0)
; CHECK: DW_TAG_template_value_parameter
; CHECK: DW_AT_name {{.*}} "F"
; CHECK: DW_AT_const_value [DW_FORM_udata] (0)
; Function Attrs: nounwind uwtable
define weak_odr void @_Z4funcILPv0ELPFvvE0ELi42EEvv() #0 {
entry:
ret void, !dbg !18
}
attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!15, !16}
!llvm.ident = !{!17}
!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang version 3.5.0 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 1} ; [ DW_TAG_compile_unit ] [/tmp/dbginfo/constant-pointers.cpp] [DW_LANG_C_plus_plus]
!1 = metadata !{metadata !"constant-pointers.cpp", metadata !"/tmp/dbginfo"}
!2 = metadata !{}
!3 = metadata !{metadata !4}
!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"func<nullptr, nullptr, 42>", metadata !"func<nullptr, nullptr, 42>", metadata !"_Z4funcILPv0ELPFvvE0ELi42EEvv", i32 2, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void ()* @_Z4funcILPv0ELPFvvE0ELi42EEvv, metadata !8, null, metadata !2, i32 2} ; [ DW_TAG_subprogram ] [line 2] [def] [func<nullptr, nullptr, 42>]
!5 = metadata !{i32 786473, metadata !1} ; [ DW_TAG_file_type ] [/tmp/dbginfo/constant-pointers.cpp]
!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
!7 = metadata !{null}
!8 = metadata !{metadata !9, metadata !11, metadata !13}
!9 = metadata !{i32 786480, null, metadata !"V", metadata !10, i8 0, null, i32 0, i32 0} ; [ DW_TAG_template_value_parameter ]
!10 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 0, null} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from ]
!11 = metadata !{i32 786480, null, metadata !"F", metadata !12, i8 0, null, i32 0, i32 0} ; [ DW_TAG_template_value_parameter ]
!12 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 0, metadata !6} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from ]
!13 = metadata !{i32 786480, null, metadata !"i", metadata !14, i32 42, null, i32 0, i32 0} ; [ DW_TAG_template_value_parameter ]
!14 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
!15 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
!16 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
!17 = metadata !{metadata !"clang version 3.5.0 "}
!18 = metadata !{i32 3, i32 0, metadata !4, null}