711f6a8603
We started attaching `DW_AT_object_pointer`s on method declarations in https://github.com/llvm/llvm-project/pull/122742. However, that caused the `.debug_info` section size to increase significantly (by around ~10% on some projects). This was mainly due to the large number of new `DW_FORM_ref4` values. This patch tries to address that regression by changing the `DW_FORM_ref4` to a `DW_FORM_implicit_const` for declarations. The value of `DW_FORM_implicit_const` will be the *index* of the object parameter in the list of formal parameters of the subprogram (i.e., if the first `DW_TAG_formal_parameter` is the object pointer, the `DW_FORM_implicit_const` would be `0`). The DWARFv5 spec only mentions the use of the `reference` attribute class to for `DW_AT_object_pointer`. So using a `DW_FORM_impilicit_const` would be an extension to (and not something mandated/specified by) the standard. Though it'd make sense to extend the wording in the spec to allow for this optimization. That way we don't pay for the 4 byte references on every attribute occurrence. In a local build of clang this barely affected the `.debug_info` section size (but did increase `.debug_abbrev` by up to 10%, which doesn't impact the total debug-info size much however). We guarded this on LLDB tuning (since using `DW_FORM_implicit_const` for this purpose may surprise consumers) and DWARFv5 (since that's where `DW_FORM_implicit_const` was first standardized).
102 lines
5.7 KiB
LLVM
102 lines
5.7 KiB
LLVM
; RUN: llc -mtriple=x86_64-apple-darwin -debugger-tune=gdb -dwarf-version=5 -filetype=obj < %s | \
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; RUN: llvm-dwarfdump -v -debug-info - | FileCheck %s --check-prefixes=CHECK,CHECK-GDB
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; RUN: llc -mtriple=x86_64-apple-darwin -debugger-tune=lldb -dwarf-version=4 -filetype=obj < %s | \
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; RUN: llvm-dwarfdump -v -debug-info - | FileCheck %s --check-prefixes=CHECK,CHECK-LLDB-DWARF4
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; RUN: llc -mtriple=x86_64-apple-darwin -debugger-tune=lldb -dwarf-version=5 -filetype=obj < %s | \
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; RUN: llvm-dwarfdump -v -debug-info - | FileCheck %s --check-prefixes=CHECK,CHECK-LLDB-DWARF5
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; CHECK: DW_TAG_formal_parameter [
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; CHECK-NOT: ""
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; CHECK: DW_TAG
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; CHECK: DW_TAG_class_type
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; CHECK: [[DECL:0x[0-9a-f]+]]: DW_TAG_subprogram
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; CHECK: DW_AT_name {{.*}} "A"
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; CHECK-LLDB-DWARF5: DW_AT_object_pointer [DW_FORM_implicit_const] (0)
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; CHECK-GDB-NOT: DW_AT_object_pointer
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; CHECK-LLDB-DWARF4-NOT: DW_AT_object_pointer
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; CHECK: DW_TAG_formal_parameter
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;
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; CHECK: DW_TAG_subprogram
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; CHECK: DW_AT_object_pointer [DW_FORM_ref4] (cu + 0x{{[0-9a-f]*}} => {[[PARAM:0x[0-9a-f]*]]})
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; CHECK: DW_AT_specification [DW_FORM_ref4] (cu + {{.*}} => {[[DECL]]}
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; CHECK: [[PARAM]]: DW_TAG_formal_parameter
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; CHECK-NOT: DW_TAG
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; CHECK: DW_AT_name
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; CHECK-SAME = "this")
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%class.A = type { i32 }
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define i32 @_Z3fooi(i32) nounwind uwtable ssp !dbg !5 {
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entry:
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%.addr = alloca i32, align 4
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%a = alloca %class.A, align 4
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store i32 %0, ptr %.addr, align 4
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call void @llvm.dbg.declare(metadata ptr %.addr, metadata !36, metadata !DIExpression()), !dbg !35
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call void @llvm.dbg.declare(metadata ptr %a, metadata !21, metadata !DIExpression()), !dbg !23
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call void @_ZN1AC1Ev(ptr %a), !dbg !24
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%1 = load i32, ptr %a, align 4, !dbg !25
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ret i32 %1, !dbg !25
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}
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declare void @llvm.dbg.declare(metadata, metadata, metadata) nounwind readnone
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define linkonce_odr void @_ZN1AC1Ev(ptr %this) unnamed_addr nounwind uwtable ssp align 2 !dbg !10 {
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entry:
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%this.addr = alloca ptr, align 8
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store ptr %this, ptr %this.addr, align 8
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call void @llvm.dbg.declare(metadata ptr %this.addr, metadata !26, metadata !DIExpression()), !dbg !28
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%this1 = load ptr, ptr %this.addr
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call void @_ZN1AC2Ev(ptr %this1), !dbg !29
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ret void, !dbg !29
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}
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define linkonce_odr void @_ZN1AC2Ev(ptr %this) unnamed_addr nounwind uwtable ssp align 2 !dbg !20 {
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entry:
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%this.addr = alloca ptr, align 8
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store ptr %this, ptr %this.addr, align 8
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call void @llvm.dbg.declare(metadata ptr %this.addr, metadata !30, metadata !DIExpression()), !dbg !31
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%this1 = load ptr, ptr %this.addr
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store i32 0, ptr %this1, align 4, !dbg !32
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ret void, !dbg !34
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}
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!38}
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!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.2 (trunk 163586) (llvm/trunk 163570)", isOptimized: false, emissionKind: FullDebug, file: !37, enums: !1, retainedTypes: !1, globals: !1, imports: !1)
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!1 = !{}
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!5 = distinct !DISubprogram(name: "foo", linkageName: "_Z3fooi", line: 7, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 7, file: !6, scope: !6, type: !7, retainedNodes: !1)
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!6 = !DIFile(filename: "bar.cpp", directory: "/Users/echristo/debug-tests")
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!7 = !DISubroutineType(types: !8)
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!8 = !{!9}
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!9 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
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!10 = distinct !DISubprogram(name: "A", linkageName: "_ZN1AC1Ev", line: 3, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 3, file: !6, scope: null, type: !11, declaration: !17, retainedNodes: !1)
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!11 = !DISubroutineType(types: !12)
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!12 = !{null, !13}
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!13 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, flags: DIFlagArtificial | DIFlagObjectPointer, baseType: !14)
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!14 = !DICompositeType(tag: DW_TAG_class_type, name: "A", line: 1, size: 32, align: 32, file: !37, elements: !15)
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!15 = !{!16, !17}
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!16 = !DIDerivedType(tag: DW_TAG_member, name: "m_a", line: 4, size: 32, align: 32, file: !37, scope: !14, baseType: !9)
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!17 = !DISubprogram(name: "A", line: 3, isLocal: false, isDefinition: false, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 3, file: !6, scope: !14, type: !11)
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!20 = distinct !DISubprogram(name: "A", linkageName: "_ZN1AC2Ev", line: 3, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 3, file: !6, scope: null, type: !11, declaration: !17, retainedNodes: !1)
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!21 = !DILocalVariable(name: "a", line: 8, scope: !22, file: !6, type: !14)
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!22 = distinct !DILexicalBlock(line: 7, column: 11, file: !6, scope: !5)
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!23 = !DILocation(line: 8, column: 5, scope: !22)
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!24 = !DILocation(line: 8, column: 6, scope: !22)
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!25 = !DILocation(line: 9, column: 3, scope: !22)
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!26 = !DILocalVariable(name: "this", line: 3, arg: 1, flags: DIFlagArtificial | DIFlagObjectPointer, scope: !10, file: !6, type: !27)
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!27 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, baseType: !14)
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!28 = !DILocation(line: 3, column: 3, scope: !10)
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!29 = !DILocation(line: 3, column: 18, scope: !10)
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!30 = !DILocalVariable(name: "this", line: 3, arg: 1, flags: DIFlagArtificial | DIFlagObjectPointer, scope: !20, file: !6, type: !27)
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!31 = !DILocation(line: 3, column: 3, scope: !20)
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!32 = !DILocation(line: 3, column: 9, scope: !33)
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!33 = distinct !DILexicalBlock(line: 3, column: 7, file: !6, scope: !20)
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!34 = !DILocation(line: 3, column: 18, scope: !33)
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!35 = !DILocation(line: 7, scope: !5)
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!36 = !DILocalVariable(name: "", line: 7, arg: 1, scope: !5, file: !6, type: !9)
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!37 = !DIFile(filename: "bar.cpp", directory: "/Users/echristo/debug-tests")
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!38 = !{i32 1, !"Debug Info Version", i32 3}
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