fea067bdfd
This patch copies @vsk's fix to instcombine from D85555 over to mem2reg. The
motivation and rationale are exactly the same: When mem2reg removes an alloca,
it erases the dbg.{addr,declare} instructions which refer to the alloca. It
would be better to instead remove all debug intrinsics which describe the
contents of the dead alloca, namely all dbg.value(<dead alloca>, ...,
DW_OP_deref)'s.
As far as I can tell, prior to D80264 these `dbg.value+deref`s would have been
silently dropped instead of being made `undef`, so we're just returning to
previous behaviour with these patches.
Testing:
`llvm-lit llvm/test` and `ninja check-clang` gave no unexpected failures. Added
3 tests, each of which covers a dbg.value deletion path in mem2reg:
mem2reg-promote-alloca-1.ll
mem2reg-promote-alloca-2.ll
mem2reg-promote-alloca-3.ll
The first is based on the dexter test inlining.c from D89543. This patch also
improves the debugging experience for loop.c from D89543, which suffers
similarly after arg promotion instead of inlining.
125 lines
6.0 KiB
LLVM
125 lines
6.0 KiB
LLVM
; RUN: opt -mem2reg %s -S -o - | FileCheck %s
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;; Check that mem2reg removes dbg.value(%local, DIExpression(DW_OP_deref...))
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;; that instcombine LowerDbgDeclare inserted before the call to 'esc' when
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;; promoting the alloca %local after 'esc' has been inlined. Without this we
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;; provide no location for 'local', even though it is provably constant
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;; throughout after inlining.
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;;
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;; $ clang reduce.c -O2 -g -emit-llvm -S -o tmp.ll -Xclang -disable-llvm-passes
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;; $ opt tmp.ll -o - -instcombine -inline -S
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;; $ cat reduce.c
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;; long a;
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;; int b;
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;; void c();
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;; __attribute__((__always_inline__))
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;; static void esc(long *e) {
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;; *e = a;
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;; c();
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;; if (b)
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;; *e = 0;
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;; }
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;;
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;; void fun() {
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;; long local = 0;
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;; esc(&local);
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;; }
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; CHECK: define dso_local void @fun()
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i64 0, metadata ![[LOCAL:[0-9]+]], metadata !DIExpression())
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; CHECK-NOT: call void @llvm.dbg.value({{.*}}, metadata ![[LOCAL]]
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; CHECK: ![[LOCAL]] = !DILocalVariable(name: "local",
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@a = dso_local global i64 0, align 8, !dbg !0
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@b = dso_local global i32 0, align 4, !dbg !6
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define dso_local void @fun() !dbg !14 {
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entry:
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%e.addr.i = alloca i64*, align 8
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%local = alloca i64, align 8
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%0 = bitcast i64* %local to i8*, !dbg !19
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call void @llvm.lifetime.start.p0i8(i64 8, i8* nonnull %0), !dbg !19
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call void @llvm.dbg.value(metadata i64 0, metadata !18, metadata !DIExpression()), !dbg !20
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store i64 0, i64* %local, align 8, !dbg !21
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call void @llvm.dbg.value(metadata i64* %local, metadata !18, metadata !DIExpression(DW_OP_deref)), !dbg !20
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%1 = bitcast i64** %e.addr.i to i8*, !dbg !26
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call void @llvm.lifetime.start.p0i8(i64 8, i8* %1), !dbg !26
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call void @llvm.dbg.value(metadata i64* %local, metadata !32, metadata !DIExpression()), !dbg !26
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store i64* %local, i64** %e.addr.i, align 8
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%2 = load i64, i64* @a, align 8, !dbg !36
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call void @llvm.dbg.value(metadata i64* %local, metadata !32, metadata !DIExpression()), !dbg !26
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store i64 %2, i64* %local, align 8, !dbg !37
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call void (...) @c(), !dbg !38
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%3 = load i32, i32* @b, align 4, !dbg !39
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%tobool.not.i = icmp eq i32 %3, 0, !dbg !39
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br i1 %tobool.not.i, label %esc.exit, label %if.then.i, !dbg !43
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if.then.i: ; preds = %entry
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%4 = load i64*, i64** %e.addr.i, align 8, !dbg !44
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call void @llvm.dbg.value(metadata i64* %4, metadata !32, metadata !DIExpression()), !dbg !26
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store i64 0, i64* %4, align 8, !dbg !45
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br label %esc.exit, !dbg !46
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esc.exit: ; preds = %entry, %if.then.i
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%5 = bitcast i64** %e.addr.i to i8*, !dbg !47
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call void @llvm.lifetime.end.p0i8(i64 8, i8* %5), !dbg !47
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%6 = bitcast i64* %local to i8*, !dbg !48
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call void @llvm.lifetime.end.p0i8(i64 8, i8* nonnull %6), !dbg !48
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ret void, !dbg !48
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}
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declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture)
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declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)
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declare void @llvm.dbg.value(metadata, metadata, metadata)
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declare !dbg !49 dso_local void @c(...)
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!llvm.dbg.cu = !{!2}
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!llvm.module.flags = !{!10, !11, !12}
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!llvm.ident = !{!13}
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!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
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!1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !9, 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: "reduce.c", directory: "/")
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!4 = !{}
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!5 = !{!0, !6}
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!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
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!7 = distinct !DIGlobalVariable(name: "b", scope: !2, file: !3, line: 2, type: !8, isLocal: false, isDefinition: true)
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!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!9 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
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!10 = !{i32 7, !"Dwarf Version", i32 4}
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!11 = !{i32 2, !"Debug Info Version", i32 3}
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!12 = !{i32 1, !"wchar_size", i32 4}
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!13 = !{!"clang version 12.0.0"}
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!14 = distinct !DISubprogram(name: "fun", scope: !3, file: !3, line: 12, type: !15, scopeLine: 12, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !17)
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!15 = !DISubroutineType(types: !16)
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!16 = !{null}
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!17 = !{!18}
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!18 = !DILocalVariable(name: "local", scope: !14, file: !3, line: 13, type: !9)
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!19 = !DILocation(line: 13, column: 3, scope: !14)
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!20 = !DILocation(line: 0, scope: !14)
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!21 = !DILocation(line: 13, column: 8, scope: !14)
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!26 = !DILocation(line: 0, scope: !27, inlinedAt: !33)
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!27 = distinct !DISubprogram(name: "esc", scope: !3, file: !3, line: 5, type: !28, scopeLine: 5, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !31)
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!28 = !DISubroutineType(types: !29)
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!29 = !{null, !30}
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!30 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
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!31 = !{!32}
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!32 = !DILocalVariable(name: "e", arg: 1, scope: !27, file: !3, line: 5, type: !30)
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!33 = distinct !DILocation(line: 14, column: 3, scope: !14)
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!36 = !DILocation(line: 6, column: 8, scope: !27, inlinedAt: !33)
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!37 = !DILocation(line: 6, column: 6, scope: !27, inlinedAt: !33)
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!38 = !DILocation(line: 7, column: 3, scope: !27, inlinedAt: !33)
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!39 = !DILocation(line: 8, column: 7, scope: !40, inlinedAt: !33)
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!40 = distinct !DILexicalBlock(scope: !27, file: !3, line: 8, column: 7)
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!43 = !DILocation(line: 8, column: 7, scope: !27, inlinedAt: !33)
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!44 = !DILocation(line: 9, column: 6, scope: !40, inlinedAt: !33)
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!45 = !DILocation(line: 9, column: 8, scope: !40, inlinedAt: !33)
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!46 = !DILocation(line: 9, column: 5, scope: !40, inlinedAt: !33)
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!47 = !DILocation(line: 10, column: 1, scope: !27, inlinedAt: !33)
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!48 = !DILocation(line: 15, column: 1, scope: !14)
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!49 = !DISubprogram(name: "c", scope: !3, file: !3, line: 3, type: !50, spFlags: DISPFlagOptimized, retainedNodes: !4)
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!50 = !DISubroutineType(types: !51)
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!51 = !{null, null}
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