e3cd498ff7
The Assignment Tracking debug-info feature is outlined in this RFC: https://discourse.llvm.org/t/ rfc-assignment-tracking-a-better-way-of-specifying-variable-locations-in-ir The inliner requires two additions: fixupAssignments - Update inlined instructions' DIAssignID metadata so that inlined DIAssignID attachments are unique to the inlined instance. trackInlinedStores - Treat inlined stores to caller-local variables (i.e. callee stores to argument pointers that point to the caller's allocas) as assignments. Track them using trackAssignments, which is the same method as is used by the AssignmentTrackingPass. This means that we're able to detect stale memory locations due to DSE after inlining. Because the stores are only tracked _after_ inlining, any DSE or movement of stores _before_ inlining will not be accounted for. This is an accepted limitation mentioned in the RFC. One change is also required: Update CloneBlock to preserve debug use-before-defs. Otherwise the assignments will be dropped due to having the intrinsic operands replaced with empty metadata (see use-before-def.ll in this patch and this related discourse post. Reviewed By: jmorse Differential Revision: https://reviews.llvm.org/D133318
80 lines
3.2 KiB
LLVM
80 lines
3.2 KiB
LLVM
; RUN: opt -passes=inline %s -S -o - -experimental-assignment-tracking \
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; RUN: | FileCheck %s
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;; Hand modified from:
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;; $ cat test.c
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;; int g = 5;
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;; static int callee() {
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;; int local = g;
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;; return local;
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;; }
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;;
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;; int fun() {
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;; return callee();
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;; }
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;;
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;; IR grabbed before inlining in:
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;; $ clang++ -O2 -g
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;; Then modified (see comment in body).
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;; NOTE: Although this reproducer is contrived, this has been observed in real
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;; builds with assignment tracking (dbg.assign intrinsics) - in fact, it caused
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;; verifier failures in some cases using assignment tracking (good). This is
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;; the simplest test I could write.
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;; use-before-defs in debug intrinsics should be preserved through inlining,
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;; or at the very least should be converted to undefs. The previous behaviour
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;; was to replace the use-before-def operand with empty metadata, which signals
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;; cleanup passes that it's okay to remove the debug intrinsic (bad). Check
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;; that this no longer happens.
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; CHECK: define dso_local i32 @fun()
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; CHECK-NEXT: entry
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 %0
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@g = dso_local local_unnamed_addr global i32 5, align 4, !dbg !0
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define dso_local i32 @fun() local_unnamed_addr #0 !dbg !11 {
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entry:
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%call = call fastcc i32 @callee(), !dbg !14
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ret i32 %call, !dbg !15
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}
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define internal fastcc i32 @callee() unnamed_addr #1 !dbg !16 {
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entry:
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;; dbg.value moved here from after %0 def.
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call void @llvm.dbg.value(metadata i32 %0, metadata !18, metadata !DIExpression()), !dbg !24
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%0 = load i32, ptr @g, align 4, !dbg !19
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ret i32 %0, !dbg !25
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}
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declare void @llvm.dbg.value(metadata, metadata, metadata) #2
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!llvm.dbg.cu = !{!2}
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!llvm.module.flags = !{!7, !8, !9}
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!llvm.ident = !{!10}
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!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
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!1 = distinct !DIGlobalVariable(name: "g", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
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!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 12.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, splitDebugInlining: false, nameTableKind: None)
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!3 = !DIFile(filename: "test.c", directory: "/")
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!4 = !{}
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!5 = !{!0}
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!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!7 = !{i32 7, !"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 12.0.0"}
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!11 = distinct !DISubprogram(name: "fun", scope: !3, file: !3, line: 7, type: !12, scopeLine: 7, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !4)
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!12 = !DISubroutineType(types: !13)
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!13 = !{!6}
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!14 = !DILocation(line: 8, column: 10, scope: !11)
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!15 = !DILocation(line: 8, column: 3, scope: !11)
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!16 = distinct !DISubprogram(name: "callee", scope: !3, file: !3, line: 2, type: !12, scopeLine: 2, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !17)
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!17 = !{!18}
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!18 = !DILocalVariable(name: "local", scope: !16, file: !3, line: 3, type: !6)
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!19 = !DILocation(line: 3, column: 15, scope: !16)
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!24 = !DILocation(line: 0, scope: !16)
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!25 = !DILocation(line: 4, column: 3, scope: !16)
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