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clang-p2996/llvm/test/Transforms/InstCombine/debuginfo-dce.ll
Jeremy Morse b33a5c7347 [DebugInfo] Don't salvage load operations (PR40628). 
Salvaging a redundant load instruction into a debug expression hides a
memory read from optimisation passes. Passes that alter memory behaviour
(such as LICM promoting memory to a register) aren't aware of these debug
memory reads and leave them unaltered, making the debug variable location
point somewhere unsafe.

Teaching passes to know about these debug memory reads would be challenging
and probably incomplete. Finding dbg.value instructions that need to be fixed
would likely be computationally expensive too, as more analysis would be
required. It's better to not generate debug-memory-reads instead, alas.

Changed tests:
 * DeadStoreElim: test for salvaging of intermediate operations contributing
   to the dead store, instead of salvaging of the redundant load,
 * GVN: remove debuginfo behaviour checks completely, this behaviour is still
   covered by other tests,
 * InstCombine: don't test for salvaged loads, we're removing that behaviour.

Differential Revision: https://reviews.llvm.org/D57962

llvm-svn: 353824
2019-02-12 10:54:30 +00:00

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; RUN: opt -instcombine %s -S -o - | FileCheck %s
; Verify that the eliminated instructions (bitcast, gep, load) are salvaged into
; a DIExpression.
;
; Originally created from the following C source and then heavily isolated/reduced.
;
; struct entry {
; struct entry *next;
; };
; void scan(struct entry *queue, struct entry *end)
; {
; struct entry *entry;
; for (entry = (struct entry *)((char *)(queue->next) - 8);
; &entry->next == end;
; entry = (struct entry *)((char *)(entry->next) - 8)) {
; }
; }
; ModuleID = '<stdin>'
source_filename = "test.c"
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.12.0"
%struct.entry = type { %struct.entry* }
; This salvage can't currently occur safely (PR40628), however if/when that's
; ever fixed, then this is definitely a piece of test coverage that should
; be maintained.
define void @salvage_load(%struct.entry** %queue) local_unnamed_addr #0 !dbg !14 {
entry:
%im_not_dead = alloca %struct.entry*
%0 = load %struct.entry*, %struct.entry** %queue, align 8, !dbg !19
%1 = load %struct.entry*, %struct.entry** %queue, align 8, !dbg !19
call void @llvm.dbg.value(metadata %struct.entry* %1, metadata !18, metadata !20), !dbg !19
; CHECK: define void @salvage_load
; CHECK-NEXT: entry:
; CHECK-NOT: dbg.value
store %struct.entry* %1, %struct.entry** %im_not_dead, align 8
ret void, !dbg !21
}
define void @salvage_bitcast(%struct.entry* %queue) local_unnamed_addr #0 !dbg !22 {
entry:
%im_not_dead = alloca i8*
%0 = bitcast %struct.entry* %queue to i8*, !dbg !23
%1 = bitcast %struct.entry* %queue to i8*, !dbg !23
call void @llvm.dbg.value(metadata i8* %1, metadata !24, metadata !20), !dbg !23
; CHECK: define void @salvage_bitcast
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @llvm.dbg.value(metadata %struct.entry* %queue,
; CHECK-SAME: metadata !DIExpression(DW_OP_plus_uconst, 0))
store i8* %1, i8** %im_not_dead, align 8
ret void, !dbg !23
}
define void @salvage_gep0(%struct.entry* %queue, %struct.entry* %end) local_unnamed_addr #0 !dbg !25 {
entry:
%im_not_dead = alloca %struct.entry**
%0 = getelementptr inbounds %struct.entry, %struct.entry* %queue, i32 -1, i32 0, !dbg !26
%1 = getelementptr inbounds %struct.entry, %struct.entry* %queue, i32 -1, i32 0, !dbg !26
call void @llvm.dbg.value(metadata %struct.entry** %1, metadata !27, metadata !20), !dbg !26
; CHECK: define void @salvage_gep0
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @llvm.dbg.value(metadata %struct.entry* %queue,
; CHECK-SAME: metadata !DIExpression(DW_OP_constu, 8, DW_OP_minus, DW_OP_plus_uconst, 0, DW_OP_stack_value))
store %struct.entry** %1, %struct.entry*** %im_not_dead, align 8
ret void, !dbg !26
}
define void @salvage_gep1(%struct.entry* %queue, %struct.entry* %end) local_unnamed_addr #0 !dbg !28 {
entry:
%im_not_dead = alloca %struct.entry**
%0 = getelementptr inbounds %struct.entry, %struct.entry* %queue, i32 -1, i32 0, !dbg !29
%1 = getelementptr inbounds %struct.entry, %struct.entry* %queue, i32 -1, i32 0, !dbg !29
call void @llvm.dbg.value(metadata %struct.entry** %1, metadata !30, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 32)), !dbg !29
; CHECK: define void @salvage_gep1
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @llvm.dbg.value(metadata %struct.entry* %queue,
; CHECK-SAME: metadata !DIExpression(DW_OP_constu, 8, DW_OP_minus, DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 32))
store %struct.entry** %1, %struct.entry*** %im_not_dead, align 8
ret void, !dbg !29
}
define void @salvage_gep2(%struct.entry* %queue, %struct.entry* %end) local_unnamed_addr #0 !dbg !31 {
entry:
%im_not_dead = alloca %struct.entry**
%0 = getelementptr inbounds %struct.entry, %struct.entry* %queue, i32 -1, i32 0, !dbg !32
%1 = getelementptr inbounds %struct.entry, %struct.entry* %queue, i32 -1, i32 0, !dbg !32
call void @llvm.dbg.value(metadata %struct.entry** %1, metadata !33, metadata !DIExpression(DW_OP_stack_value)), !dbg !32
; CHECK: define void @salvage_gep2
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @llvm.dbg.value(metadata %struct.entry* %queue,
; CHECK-SAME: metadata !DIExpression(DW_OP_constu, 8, DW_OP_minus, DW_OP_stack_value))
store %struct.entry** %1, %struct.entry*** %im_not_dead, align 8
ret void, !dbg !32
}
; Function Attrs: nounwind readnone
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
attributes #0 = { nounwind ssp uwtable }
attributes #1 = { nounwind readnone }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!10, !11, !12}
!llvm.ident = !{!13}
!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)
!1 = !DIFile(filename: "test.c", directory: "/")
!2 = !{}
!3 = !{!4, !8}
!4 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !5, size: 64)
!5 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "entry", file: !1, line: 1, size: 64, elements: !6)
!6 = !{!7}
!7 = !DIDerivedType(tag: DW_TAG_member, name: "next", scope: !5, file: !1, line: 2, baseType: !4, size: 64)
!8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
!9 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
!10 = !{i32 2, !"Dwarf Version", i32 4}
!11 = !{i32 2, !"Debug Info Version", i32 3}
!12 = !{i32 1, !"PIC Level", i32 2}
!13 = !{!"clang version 5.0.0 (trunk 297628) (llvm/trunk 297643)"}
!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, retainedNodes: !17)
!15 = !DISubroutineType(types: !16)
!16 = !{null, !4, !4}
!17 = !{!18}
!18 = !DILocalVariable(name: "entry", scope: !14, file: !1, line: 6, type: !4)
!19 = !DILocation(line: 6, column: 17, scope: !14)
!20 = !DIExpression(DW_OP_plus_uconst, 0)
!21 = !DILocation(line: 11, column: 1, scope: !14)
!22 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !17)
!23 = !DILocation(line: 6, column: 17, scope: !22)
!24 = !DILocalVariable(name: "entry", scope: !22, file: !1, line: 6, type: !4)
!25 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !17)
!26 = !DILocation(line: 6, column: 17, scope: !25)
!27 = !DILocalVariable(name: "entry", scope: !25, file: !1, line: 6, type: !4)
!28 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !17)
!29 = !DILocation(line: 6, column: 17, scope: !28)
!30 = !DILocalVariable(name: "entry", scope: !28, file: !1, line: 6, type: !4)
!31 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !17)
!32 = !DILocation(line: 6, column: 17, scope: !31)
!33 = !DILocalVariable(name: "entry", scope: !31, file: !1, line: 6, type: !4)
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