47ea6478ed
[Reapplies r297971 and punting on finding a better API for findDbgValues()] This patch improves debug info quality in InstCombine by looking at values that are about to be deleted, checking whether there are any dbg.value instrinsics referring to them, and potentially encoding the semantics of the deleted instruction into the dbg.value's DIExpression. In the example in the testcase (which was extracted from XNU) there is a sequence of %4 = load %struct.entry*, %struct.entry** %next2, align 8, !dbg !41 %5 = bitcast %struct.entry* %4 to i8*, !dbg !42 %add.ptr4 = getelementptr inbounds i8, i8* %5, i64 -8, !dbg !43 %6 = bitcast i8* %add.ptr4 to %struct.entry*, !dbg !44 call void @llvm.dbg.value(metadata %struct.entry* %6, i64 0, metadata !20, metadata !21), !dbg 34 When these instructions are eliminated by instcombine one after another, we can still salvage the otherwise dead debug info: - Bitcasts have no effect, so have the dbg.value point to operand(0) - Loads can be expressed via a DW_OP_deref - Constant gep instructions can be replaced by DWARF expression arithmetic The API introduced by this patch is not specific to instcombine and can be useful in other places, too. rdar://problem/30725338 Differential Revision: https://reviews.llvm.org/D30919 llvm-svn: 297994
107 lines
4.6 KiB
LLVM
107 lines
4.6 KiB
LLVM
; RUN: opt -instcombine %s -S -o - | FileCheck %s
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; Verify that the eliminated instructions (bitcast, gep, load) are salvaged into
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; a DIExpression.
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;
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; Originally created from the following C source and then heavily isolated/reduced.
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;
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; struct entry {
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; struct entry *next;
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; };
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; void scan(struct entry *queue, struct entry *end)
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; {
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; struct entry *entry;
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; for (entry = (struct entry *)((char *)(queue->next) - 8);
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; &entry->next == end;
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; entry = (struct entry *)((char *)(entry->next) - 8)) {
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; }
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; }
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; ModuleID = '<stdin>'
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source_filename = "test.c"
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-apple-macosx10.12.0"
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%struct.entry = type { %struct.entry* }
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; Function Attrs: nounwind ssp uwtable
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define void @salvage_load(%struct.entry** %queue) local_unnamed_addr #0 !dbg !14 {
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entry:
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%im_not_dead = alloca %struct.entry*
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%0 = load %struct.entry*, %struct.entry** %queue, align 8, !dbg !19
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%1 = load %struct.entry*, %struct.entry** %queue, align 8, !dbg !19
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call void @llvm.dbg.value(metadata %struct.entry* %1, i64 0, metadata !18, metadata !20), !dbg !19
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; CHECK: define void @salvage_load
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call void @llvm.dbg.value(metadata %struct.entry** %queue, i64 0,
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; CHECK-SAME: metadata ![[LOAD_EXPR:[0-9]+]])
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store %struct.entry* %1, %struct.entry** %im_not_dead, align 8
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ret void, !dbg !21
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}
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; Function Attrs: nounwind ssp uwtable
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define void @salvage_bitcast(%struct.entry* %queue) local_unnamed_addr #0 !dbg !14 {
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entry:
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%im_not_dead = alloca i8*
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%0 = bitcast %struct.entry* %queue to i8*, !dbg !19
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%1 = bitcast %struct.entry* %queue to i8*, !dbg !19
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call void @llvm.dbg.value(metadata i8* %1, i64 0, metadata !18, metadata !20), !dbg !19
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; CHECK: define void @salvage_bitcast
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call void @llvm.dbg.value(metadata %struct.entry* %queue, i64 0,
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; CHECK-SAME: metadata ![[BITCAST_EXPR:[0-9]+]])
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store i8* %1, i8** %im_not_dead, align 8
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ret void, !dbg !21
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}
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; Function Attrs: nounwind ssp uwtable
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define void @salvage_gep(%struct.entry* %queue, %struct.entry* %end) local_unnamed_addr #0 !dbg !14 {
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entry:
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%im_not_dead = alloca %struct.entry**
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%0 = getelementptr inbounds %struct.entry, %struct.entry* %queue, i32 -1, i32 0, !dbg !19
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%1 = getelementptr inbounds %struct.entry, %struct.entry* %queue, i32 -1, i32 0, !dbg !19
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call void @llvm.dbg.value(metadata %struct.entry** %1, i64 0, metadata !18, metadata !20), !dbg !19
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; CHECK: define void @salvage_gep
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call void @llvm.dbg.value(metadata %struct.entry* %queue, i64 0,
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; CHECK-SAME: metadata ![[GEP_EXPR:[0-9]+]])
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store %struct.entry** %1, %struct.entry*** %im_not_dead, align 8
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ret void, !dbg !21
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}
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; CHECK: ![[LOAD_EXPR]] = !DIExpression(DW_OP_deref, DW_OP_plus, 0)
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; CHECK: ![[BITCAST_EXPR]] = !DIExpression(DW_OP_plus, 0)
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; CHECK: ![[GEP_EXPR]] = !DIExpression(DW_OP_minus, 8, DW_OP_plus, 0)
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; Function Attrs: nounwind readnone
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declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
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attributes #0 = { nounwind ssp uwtable }
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attributes #1 = { nounwind readnone }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!10, !11, !12}
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!llvm.ident = !{!13}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 5.0.0 (trunk 297628) (llvm/trunk 297643)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3)
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!1 = !DIFile(filename: "test.c", directory: "/")
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!2 = !{}
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!3 = !{!4, !8}
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!4 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !5, size: 64)
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!5 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "entry", file: !1, line: 1, size: 64, elements: !6)
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!6 = !{!7}
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!7 = !DIDerivedType(tag: DW_TAG_member, name: "next", scope: !5, file: !1, line: 2, baseType: !4, size: 64)
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!8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
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!9 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
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!10 = !{i32 2, !"Dwarf Version", i32 4}
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!11 = !{i32 2, !"Debug Info Version", i32 3}
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!12 = !{i32 1, !"PIC Level", i32 2}
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!13 = !{!"clang version 5.0.0 (trunk 297628) (llvm/trunk 297643)"}
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!14 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !17)
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!15 = !DISubroutineType(types: !16)
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!16 = !{null, !4, !4}
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!17 = !{!18}
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!18 = !DILocalVariable(name: "entry", scope: !14, file: !1, line: 6, type: !4)
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!19 = !DILocation(line: 6, column: 17, scope: !14)
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!20 = !DIExpression(DW_OP_plus, 0)
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!21 = !DILocation(line: 11, column: 1, scope: !14)
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