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[AsmPrinter] Handle qualified unnamed types in CodeView printer

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When attempting to compile the following Objective-C++ code with
CodeView debug info:

  void (^b)(void) = []() {};

The generated debug metadata contains a structure like the following:

  !43 = !DICompositeType(tag: DW_TAG_structure_type, name: "__block_literal_1", scope: !6, file: !6, line: 1, size: 168, elements: !44)
  !44 = !{!45, !46, !47, !48, !49, !52}
  ...
  !52 = !DIDerivedType(tag: DW_TAG_member, scope: !6, file: !6, line: 1, baseType: !53, size: 8, offset: 160, flags: DIFlagPublic)
  !53 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !54)
  !54 = !DICompositeType(tag: DW_TAG_class_type, file: !6, line: 1, flags: DIFlagFwdDecl)

Note that the member node (!52) is unnamed, but rather than pointing to
a DICompositeType directly, it points to a DIDerivedType with tag
DW_TAG_const_type, which then points to the DICompositeType. However,
the CodeView assembly printer currently assumes that the base type for
an unnamed member will always be a DICompositeType, and attempts to
perform that cast, which triggers an assertion failure, since in this
case the base type is actually a DIDerivedType, not a DICompositeType
(and we would have to get the base type of the DIDerivedType to reach
the DICompositeType). I think the debug metadata being generated by the
frontend is correct (or at least plausible), and the CodeView printer
needs to handle this case.

This patch teaches the CodeView printer to unwrap any qualifier types.
The qualifiers are just dropped for now. Ideally, they would be applied
to the added indirect members instead, but this occurs infrequently
enough that adding the logic to handle the qualifiers correctly isn't
worth it for now. A FIXME is added to note this.

Additionally, Reid pointed out that the underlying assumption that an
unnamed member must be a composite type is itself incorrect and may not
hold for all frontends. Therefore, after all qualifiers have been
stripped, check if the resulting type is in fact a DICompositeType and
just return if it isn't, rather than assuming the type and crashing if
that assumption is violated.

Differential Revision: https://reviews.llvm.org/D43803

llvm-svn: 326255
This commit is contained in:
Shoaib Meenai 2018-02-27 21:48:41 +00:00
parent da45b93b33
commit 5857156230
2 changed files with 85 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
View File

@ -1814,12 +1814,33 @@ void CodeViewDebug::collectMemberInfo(ClassInfo &Info,
Info.Members.push_back({DDTy, 0});
return;
}
// An unnamed member must represent a nested struct or union. Add all the
// indirect fields to the current record.
// An unnamed member may represent a nested struct or union. Attempt to
// interpret the unnamed member as a DICompositeType possibly wrapped in
// qualifier types. Add all the indirect fields to the current record if that
// succeeds, and drop the member if that fails.
assert((DDTy->getOffsetInBits() % 8) == 0 && "Unnamed bitfield member!");
uint64_t Offset = DDTy->getOffsetInBits();
const DIType *Ty = DDTy->getBaseType().resolve();
const DICompositeType *DCTy = cast<DICompositeType>(Ty);
bool FullyResolved = false;
while (!FullyResolved) {
switch (Ty->getTag()) {
case dwarf::DW_TAG_const_type:
case dwarf::DW_TAG_volatile_type:
// FIXME: we should apply the qualifier types to the indirect fields
// rather than dropping them.
Ty = cast<DIDerivedType>(Ty)->getBaseType().resolve();
break;
default:
FullyResolved = true;
break;
}
}
const DICompositeType *DCTy = dyn_cast<DICompositeType>(Ty);
if (!DCTy)
return;
ClassInfo NestedInfo = collectClassInfo(DCTy);
for (const ClassInfo::MemberInfo &IndirectField : NestedInfo.Members)
Info.Members.push_back(

61
test/DebugInfo/COFF/const-unnamed-member.ll Normal file
View File

@ -0,0 +1,61 @@
; RUN: llc -filetype=obj < %s | llvm-readobj -codeview - | FileCheck %s
; Objective-C++ source demonstrating the issue:
; void (^b)(void) = []() {};
; C++ source derived and modified from:
; struct S {
; struct {
; int a;
; };
; } s;
; CHECK: CodeViewTypes [
; CHECK: FieldList ([[S_fl:.*]]) {
; CHECK: TypeLeafKind: LF_FIELDLIST (0x1203)
; CHECK: DataMember {
; CHECK: Type: int (0x74)
; CHECK: FieldOffset: 0x0
; CHECK: Name: a
; CHECK: }
; CHECK: }
; CHECK: Struct ({{.*}}) {
; CHECK: TypeLeafKind: LF_STRUCTURE (0x1505)
; CHECK: MemberCount: 2
; CHECK: FieldList: <field list> ([[S_fl]])
; CHECK: SizeOf: 4
; CHECK: Name: S
; CHECK: LinkageName: .?AUS@@
; CHECK: }
target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
target triple = "i686--windows-msvc19.11.0"
%struct.S = type { %struct.anon }
%struct.anon = type { i32 }
@"\01?s@@3US@@A" = dso_local global %struct.S zeroinitializer, align 4, !dbg !0
!llvm.dbg.cu = !{!2}
!llvm.module.flags = !{!13, !14, !15, !16}
!llvm.ident = !{!17}
!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = distinct !DIGlobalVariable(name: "s", linkageName: "\01?s@@3US@@A", scope: !2, file: !3, line: 5, type: !6, isLocal: false, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "clang version 7.0.0 (trunk 325940) (llvm/trunk 325939)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
!3 = !DIFile(filename: "/tmp/ugh.cpp", directory: "/home/smeenai/llvm/build/llvm/Debug", checksumkind: CSK_MD5, checksum: "8256b51d95df0b5e42b848a3afe9cbda")
!4 = !{}
!5 = !{!0}
!6 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S", file: !3, line: 1, size: 32, flags: DIFlagTypePassByValue, elements: !7, identifier: ".?AUS@@")
!7 = !{!8, !12}
!8 = distinct !DICompositeType(tag: DW_TAG_structure_type, scope: !6, file: !3, line: 2, size: 32, flags: DIFlagTypePassByValue, elements: !9, identifier: ".?AU<unnamed-type-$S1>@S@@")
!9 = !{!10}
!10 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !8, file: !3, line: 3, baseType: !11, size: 32)
!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!12 = !DIDerivedType(tag: DW_TAG_member, scope: !6, file: !3, line: 2, baseType: !18, size: 32) ; !8 changed to !18
!13 = !{i32 1, !"NumRegisterParameters", i32 0}
!14 = !{i32 2, !"CodeView", i32 1}
!15 = !{i32 2, !"Debug Info Version", i32 3}
!16 = !{i32 1, !"wchar_size", i32 2}
!17 = !{!"clang version 7.0.0 (trunk 325940) (llvm/trunk 325939)"}
!18 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !8) ; added manually