[PATCH] D38830: [DWARF] Fix bad comparator in sortGlobalExprs.

Thu Oct 12 03:44:37 PDT 2017

uabelho added a comment.

In https://reviews.llvm.org/D38830#895692, @bjope wrote:

> I also think that creating a test case might be troublesome. Mikael Holmén had some reproducer for this, but I doubt that it still works.

We have this:

; RUN: llc -o /dev/null %s

; Don't crash. It would of course be nice to also check that the produced
; Dwarf info is not rubbish.

@f1.a.0 = external unnamed_addr global i16, align 1, !dbg !0
@f1.a.1 = external unnamed_addr global i16, align 1, !dbg !30
@f1.a.2 = external unnamed_addr global i16, align 1, !dbg !31
@f1.a.3 = external unnamed_addr global i16, align 1, !dbg !32
@f1.a.4 = external unnamed_addr global i1, align 1, !dbg !33
@f1.a.5 = external unnamed_addr global i16, align 1, !dbg !34
@f1.a.6 = external unnamed_addr global i16, align 1, !dbg !35
@f1.a.7 = external unnamed_addr global i16, align 1, !dbg !36
@f1.a.8 = external unnamed_addr global i16, align 1, !dbg !37
@f1.a.9 = external unnamed_addr global i16, align 1, !dbg !38
@f1.a.10 = external unnamed_addr global i16, align 1, !dbg !39
@f1.a.11 = external unnamed_addr global i16, align 1, !dbg !40
@f1.a.12 = external unnamed_addr global i16, align 1, !dbg !41
@f1.a.13 = external unnamed_addr global i16, align 1, !dbg !42
@f1.a.14 = external unnamed_addr global i16, align 1, !dbg !43
@f1.a.15 = external unnamed_addr global i1, align 1, !dbg !49
@f1.a.16 = external unnamed_addr global i16, align 1, !dbg !44

!llvm.dbg.cu = !{!6}
!llvm.module.flags = !{!45, !46, !47}
!llvm.ident = !{!48}

!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 0, 16))
!1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 26, type: !10, isLocal: true, isDefinition: true)
!2 = distinct !DISubprogram(name: "f1", scope: !3, file: !3, line: 24, type: !4, isLocal: false, isDefinition: true, scopeLine: 25, flags: DIFlagPrototyped, isOptimized: true, unit: !6, variables: !7)
!3 = !DIFile(filename: "foo.c", directory: "/bar")
!4 = !DISubroutineType(types: !5)
!5 = !{null}
!6 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "my compiler", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !7, globals: !8)
!7 = !{}
!8 = !{!9}
!9 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s1", file: !3, line: 1, size: 272, elements: !11)
!11 = !{!12, !14, !15, !16, !17, !18, !19, !20, !21, !22, !23, !24, !25, !26, !27, !28, !29}
!12 = !DIDerivedType(tag: DW_TAG_member, name: "i01", scope: !10, file: !3, line: 4, baseType: !13, size: 8, offset: 6, flags: DIFlagBitField, extraData: i64 0)
!13 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
!14 = !DIDerivedType(tag: DW_TAG_member, name: "i02", scope: !10, file: !3, line: 5, baseType: !13, size: 8, offset: 16, flags: DIFlagBitField, extraData: i64 16)
!15 = !DIDerivedType(tag: DW_TAG_member, name: "i03", scope: !10, file: !3, line: 6, baseType: !13, size: 15, offset: 32, flags: DIFlagBitField, extraData: i64 32)
!16 = !DIDerivedType(tag: DW_TAG_member, name: "i04", scope: !10, file: !3, line: 7, baseType: !13, size: 4, offset: 48, flags: DIFlagBitField, extraData: i64 48)
!17 = !DIDerivedType(tag: DW_TAG_member, name: "i05", scope: !10, file: !3, line: 8, baseType: !13, size: 16, offset: 64)
!18 = !DIDerivedType(tag: DW_TAG_member, name: "i06", scope: !10, file: !3, line: 9, baseType: !13, size: 13, offset: 80, flags: DIFlagBitField, extraData: i64 80)
!19 = !DIDerivedType(tag: DW_TAG_member, name: "i07", scope: !10, file: !3, line: 10, baseType: !13, size: 4, offset: 96, flags: DIFlagBitField, extraData: i64 96)
!20 = !DIDerivedType(tag: DW_TAG_member, name: "i08", scope: !10, file: !3, line: 11, baseType: !13, size: 13, offset: 112, flags: DIFlagBitField, extraData: i64 112)
!21 = !DIDerivedType(tag: DW_TAG_member, name: "i09", scope: !10, file: !3, line: 12, baseType: !13, size: 10, offset: 128, flags: DIFlagBitField, extraData: i64 128)
!22 = !DIDerivedType(tag: DW_TAG_member, name: "i10", scope: !10, file: !3, line: 13, baseType: !13, size: 15, offset: 144, flags: DIFlagBitField, extraData: i64 144)
!23 = !DIDerivedType(tag: DW_TAG_member, name: "i11", scope: !10, file: !3, line: 15, baseType: !13, size: 5, offset: 168, flags: DIFlagBitField, extraData: i64 160)
!24 = !DIDerivedType(tag: DW_TAG_member, name: "i12", scope: !10, file: !3, line: 16, baseType: !13, size: 6, offset: 176, flags: DIFlagBitField, extraData: i64 176)
!25 = !DIDerivedType(tag: DW_TAG_member, name: "i13", scope: !10, file: !3, line: 17, baseType: !13, size: 16, offset: 192)
!26 = !DIDerivedType(tag: DW_TAG_member, name: "i14", scope: !10, file: !3, line: 18, baseType: !13, size: 5, offset: 208, flags: DIFlagBitField, extraData: i64 208)
!27 = !DIDerivedType(tag: DW_TAG_member, name: "i15", scope: !10, file: !3, line: 19, baseType: !13, size: 14, offset: 224, flags: DIFlagBitField, extraData: i64 224)
!28 = !DIDerivedType(tag: DW_TAG_member, name: "i16", scope: !10, file: !3, line: 20, baseType: !13, size: 16, offset: 240)
!29 = !DIDerivedType(tag: DW_TAG_member, name: "i17", scope: !10, file: !3, line: 21, baseType: !13, size: 4, offset: 256, flags: DIFlagBitField, extraData: i64 256)
!30 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 16, 16))
!31 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 32, 16))
!32 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 48, 16))
!33 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_deref, DW_OP_constu, 1, DW_OP_plus, DW_OP_constu, 0, DW_OP_plus, DW_OP_stack_value))
!34 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 80, 16))
!35 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 96, 16))
!36 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 112, 16))
!37 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 128, 16))
!38 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 144, 16))
!39 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 160, 16))
!40 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 176, 16))
!41 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 192, 16))
!42 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 208, 16))
!43 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 224, 16))
!44 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_LLVM_fragment, 256, 16))
!49 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_deref, DW_OP_constu, 1, DW_OP_plus, DW_OP_constu, 0, DW_OP_plus, DW_OP_stack_value))

!45 = !{i32 2, !"Dwarf Version", i32 4}
!46 = !{i32 2, !"Debug Info Version", i32 3}
!47 = !{i32 1, !"wchar_size", i32 1}
!48 = !{!"clang version 6.0.0"}

With an llc compiled with 3.6.0 the above input makes llc hit an assert
llc: ../lib/CodeGen/AsmPrinter/DwarfExpression.cpp:405: void llvm::DwarfExpression::addFragmentOffset(const llvm::DIExpression *): Assertion `FragmentOffset >= OffsetInBits && "overlapping or duplicate fragments"' failed.

However, if I compile llc with some gcc version, I don't hit the assert, so it's not very stable.

Applying this patch makes the crash go away even if I compile with clang 3.6.0.

Repository:
  rL LLVM

https://reviews.llvm.org/D38830