[BPF] Permit all user instructed offset relocatiions
Currently, not all user specified relocations (with clang intrinsic __builtin_preserve_access_index()) will turn into relocations. In the current implementation, a __builtin_preserve_access_index() chain is turned into relocation only if the result of the clang intrinsic is used in a function call or a nonzero offset computation of getelementptr. For all other cases, the relocatiion request is ignored and the __builtin_preserve_access_index() is turned into regular getelementptr instructions. The main reason is to mimic bpf_probe_read() requirement. But there are other use cases where relocatable offset is generated but not used for bpf_probe_read(). This patch relaxed previous constraints when to generate relocations. Now, all user __builtin_preserve_access_index() will have relocations generated. Differential Revision: https://reviews.llvm.org/D67688 llvm-svn: 372198
This commit is contained in:
Yonghong Song
parent
4a07336a88
commit
c68ee0ce70
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@ -375,6 +375,8 @@ void BPFAbstractMemberAccess::traceAICall(CallInst *Call, uint32_t Kind,
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traceGEP(GI, Call, Kind, ParentMeta, ParentAI);
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else
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BaseAICalls[Call] = Kind;
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} else {
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BaseAICalls[Call] = Kind;
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}
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}
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}
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@ -406,6 +408,8 @@ void BPFAbstractMemberAccess::traceBitCast(BitCastInst *BitCast,
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traceGEP(GI, Parent, Kind, ParentMeta, ParentAI);
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else
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BaseAICalls[Parent] = Kind;
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} else {
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BaseAICalls[Parent] = Kind;
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}
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}
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}
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@ -436,6 +440,8 @@ void BPFAbstractMemberAccess::traceGEP(GetElementPtrInst *GEP, CallInst *Parent,
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traceGEP(GI, Parent, Kind, ParentMeta, ParentAI);
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else
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BaseAICalls[Parent] = Kind;
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} else {
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BaseAICalls[Parent] = Kind;
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}
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}
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}
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@ -0,0 +1,82 @@
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; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck %s
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;
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; Source Code:
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; #define _(x) (__builtin_preserve_access_index(x))
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; struct s {int a; int b;};
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; int test(struct s *arg) { return *(const int *)_(&arg->b); }
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; Compiler flag to generate IR:
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; clang -target bpf -S -O2 -g -emit-llvm test.c
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%struct.s = type { i32, i32 }
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; Function Attrs: nounwind readonly
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define dso_local i32 @test(%struct.s* readonly %arg) local_unnamed_addr #0 !dbg !11 {
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entry:
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call void @llvm.dbg.value(metadata %struct.s* %arg, metadata !20, metadata !DIExpression()), !dbg !21
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%0 = tail call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.ss(%struct.s* %arg, i32 1, i32 1), !dbg !22, !llvm.preserve.access.index !15
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%1 = load i32, i32* %0, align 4, !dbg !23, !tbaa !24
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ret i32 %1, !dbg !28
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}
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; CHECK-LABEL: test
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; CHECK: r2 = 4
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; CHECK: r1 += r2
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; CHECK: r0 = *(u32 *)(r1 + 0)
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; CHECK: exit
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;
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; CHECK: .long 1 # BTF_KIND_STRUCT(id = 2)
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;
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; CHECK: .byte 115 # string offset=1
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; CHECK: .ascii ".text" # string offset=20
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; CHECK: .ascii "0:1" # string offset=26
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;
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; CHECK: .long 12 # OffsetReloc
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; CHECK-NEXT: .long 20 # Offset reloc section string offset=20
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; CHECK-NEXT: .long 1
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; CHECK-NEXT: .long .Ltmp{{[0-9]+}}
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; CHECK-NEXT: .long 2
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; CHECK-NEXT: .long 26
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; Function Attrs: nounwind readnone
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declare i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.ss(%struct.s*, i32, i32) #1
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; Function Attrs: nounwind readnone speculatable willreturn
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declare void @llvm.dbg.value(metadata, metadata, metadata) #2
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attributes #0 = { nounwind readonly "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
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attributes #1 = { nounwind readnone }
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attributes #2 = { nounwind readnone speculatable willreturn }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!7, !8, !9}
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!llvm.ident = !{!10}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0 (https://github.com/llvm/llvm-project.git 6e353b4df3aa452ed4741a5e5caea02b1a876d8c)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, nameTableKind: None)
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!1 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/work/tests/core")
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!2 = !{}
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!3 = !{!4}
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!4 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !5, size: 64)
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!5 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !6)
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!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!7 = !{i32 2, !"Dwarf Version", i32 4}
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!8 = !{i32 2, !"Debug Info Version", i32 3}
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!9 = !{i32 1, !"wchar_size", i32 4}
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!10 = !{!"clang version 10.0.0 (https://github.com/llvm/llvm-project.git 6e353b4df3aa452ed4741a5e5caea02b1a876d8c)"}
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!11 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 3, type: !12, scopeLine: 3, flags: DIFlagPrototyped, isDefinition: true, isOptimized: true, unit: !0, retainedNodes: !19)
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!12 = !DISubroutineType(types: !13)
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!13 = !{!6, !14}
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!14 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !15, size: 64)
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!15 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s", file: !1, line: 2, size: 64, elements: !16)
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!16 = !{!17, !18}
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!17 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !15, file: !1, line: 2, baseType: !6, size: 32)
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!18 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !15, file: !1, line: 2, baseType: !6, size: 32, offset: 32)
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!19 = !{!20}
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!20 = !DILocalVariable(name: "arg", arg: 1, scope: !11, file: !1, line: 3, type: !14)
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!21 = !DILocation(line: 0, scope: !11)
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!22 = !DILocation(line: 3, column: 48, scope: !11)
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!23 = !DILocation(line: 3, column: 34, scope: !11)
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!24 = !{!25, !25, i64 0}
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!25 = !{!"int", !26, i64 0}
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!26 = !{!"omnipotent char", !27, i64 0}
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!27 = !{!"Simple C/C++ TBAA"}
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!28 = !DILocation(line: 3, column: 27, scope: !11)
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@ -0,0 +1,76 @@
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; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck %s
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;
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; Source Code:
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; #define _(x) (__builtin_preserve_access_index(x))
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; struct s {int a; int b;};
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; const void *test(struct s *arg) { return _(&arg->b); }
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; Compiler flag to generate IR:
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; clang -target bpf -S -O2 -g -emit-llvm test.c
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%struct.s = type { i32, i32 }
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; Function Attrs: nounwind readnone
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define dso_local i8* @test(%struct.s* readnone %arg) local_unnamed_addr #0 !dbg !7 {
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entry:
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call void @llvm.dbg.value(metadata %struct.s* %arg, metadata !19, metadata !DIExpression()), !dbg !20
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%0 = tail call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.ss(%struct.s* %arg, i32 1, i32 1), !dbg !21, !llvm.preserve.access.index !13
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%1 = bitcast i32* %0 to i8*, !dbg !21
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ret i8* %1, !dbg !22
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}
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; CHECK-LABEL: test
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; CHECK: r0 = r1
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; CHECK: r1 = 4
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; CHECK: r0 += r1
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; CHECK: exit
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;
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; CHECK: .long 1 # BTF_KIND_STRUCT(id = 2)
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;
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; CHECK: .byte 115 # string offset=1
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; CHECK: .ascii ".text" # string offset=20
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; CHECK: .ascii "0:1" # string offset=63
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;
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; CHECK: .long 12 # OffsetReloc
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; CHECK-NEXT: .long 20 # Offset reloc section string offset=20
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; CHECK-NEXT: .long 1
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; CHECK-NEXT: .long .Ltmp{{[0-9]+}}
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; CHECK-NEXT: .long 2
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; CHECK-NEXT: .long 63
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; Function Attrs: nounwind readnone
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declare i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.ss(%struct.s*, i32, i32) #1
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; Function Attrs: nounwind readnone speculatable willreturn
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declare void @llvm.dbg.value(metadata, metadata, metadata) #2
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attributes #0 = { nounwind readnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
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attributes #1 = { nounwind readnone }
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attributes #2 = { nounwind readnone speculatable willreturn }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!3, !4, !5}
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!llvm.ident = !{!6}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0 (https://github.com/llvm/llvm-project.git 6e353b4df3aa452ed4741a5e5caea02b1a876d8c)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
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!1 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/work/tests/core")
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!2 = !{}
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!3 = !{i32 2, !"Dwarf Version", i32 4}
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!4 = !{i32 2, !"Debug Info Version", i32 3}
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!5 = !{i32 1, !"wchar_size", i32 4}
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!6 = !{!"clang version 10.0.0 (https://github.com/llvm/llvm-project.git 6e353b4df3aa452ed4741a5e5caea02b1a876d8c)"}
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!7 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 3, type: !8, scopeLine: 3, flags: DIFlagPrototyped, isDefinition: true, isOptimized: true, unit: !0, retainedNodes: !18)
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!8 = !DISubroutineType(types: !9)
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!9 = !{!10, !12}
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!10 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !11, size: 64)
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!11 = !DIDerivedType(tag: DW_TAG_const_type, baseType: null)
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!12 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 64)
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!13 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s", file: !1, line: 2, size: 64, elements: !14)
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!14 = !{!15, !17}
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!15 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !13, file: !1, line: 2, baseType: !16, size: 32)
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!16 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!17 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !13, file: !1, line: 2, baseType: !16, size: 32, offset: 32)
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!18 = !{!19}
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!19 = !DILocalVariable(name: "arg", arg: 1, scope: !7, file: !1, line: 3, type: !12)
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!20 = !DILocation(line: 0, scope: !7)
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!21 = !DILocation(line: 3, column: 42, scope: !7)
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!22 = !DILocation(line: 3, column: 35, scope: !7)
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