3feea34d77
A ValueAsMetadata may be replaced with nullptr for several reasons including
deleting (certain) values and value remapping a use-before-def. In the case of
a MetadataAsValue user, handleChangedOperand intercepts and replaces the
metadata with an empty tuple (!{}).
At the moment, an empty metadata operand in a debug intrinsics signals that it
can be deleted.
Given that we end up with empty metadata operands in circumstances where the
Value has been "lost" the current behaviour can lead to incorrect variable
locations. Instead, we should treat empty metadata as meaning "there is no
location for the variable" (the same as we currently treat undef operands).
This patch removes the deletion logic from wouldInstructionBeTriviallyDead.
Related to https://discourse.llvm.org/t/auto-undef-debug-uses-of-a-deleted-value
Reviewed By: StephenTozer
Differential Revision: https://reviews.llvm.org/D140901
38 lines
1.6 KiB
LLVM
38 lines
1.6 KiB
LLVM
; RUN: opt -passes=dce -S %s -o - | FileCheck %s
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;; Check that DCE doesn't remove a dbg intrinsic that has an empty metadata
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;; operand.
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; CHECK: call void @llvm.dbg.declare(metadata ![[EMPTY:[0-9]+]],
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; CHECK: ![[EMPTY]] = !{}
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define dso_local void @fun() local_unnamed_addr #0 !dbg !9 {
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entry:
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call void @llvm.dbg.declare(metadata !{}, metadata !13, metadata !DIExpression()), !dbg !15
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ret void, !dbg !16
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}
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declare void @llvm.dbg.declare(metadata, metadata, metadata)
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!2, !3, !4, !5, !6, !7}
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!llvm.ident = !{!8}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 16.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
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!1 = !DIFile(filename: "test.c", directory: "/")
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!2 = !{i32 7, !"Dwarf Version", i32 5}
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!3 = !{i32 2, !"Debug Info Version", i32 3}
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!4 = !{i32 1, !"wchar_size", i32 4}
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!5 = !{i32 8, !"PIC Level", i32 2}
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!6 = !{i32 7, !"PIE Level", i32 2}
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!7 = !{i32 7, !"uwtable", i32 2}
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!8 = !{!"clang version 16.0.0"}
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!9 = distinct !DISubprogram(name: "fun", scope: !1, file: !1, line: 1, type: !10, scopeLine: 1, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
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!10 = !DISubroutineType(types: !11)
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!11 = !{null}
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!12 = !{!13}
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!13 = !DILocalVariable(name: "a", scope: !9, file: !1, line: 1, type: !14)
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!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!15 = !DILocation(line: 1, column: 18, scope: !9)
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!16 = !DILocation(line: 1, column: 21, scope: !9)
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