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llvm-project/llvm/test/Transforms/DCE/dbg-value-removal.ll

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[BasicBlockUtils] Add utility to remove redundant dbg.value instrs Summary: Add a RemoveRedundantDbgInstrs to BasicBlockUtils with the goal to remove redundant dbg intrinsics from a basic block. This can be useful after various transforms, as it might be simpler to do a filtering of dbg intrinsics after the transform than during the transform. One primary use case would be to replace a too aggressive removal done by MergeBlockIntoPredecessor, seen at loop rotate (not done in this patch). The elimination algorithm currently focuses on dbg.value intrinsics and is doing two iterations over the BB. First we iterate backward starting at the last instruction in the BB. Whenever a consecutive sequence of dbg.value instructions are found we keep the last dbg.value for each variable found (variable fragments are identified using the {DILocalVariable, FragmentInfo, inlinedAt} triple as given by the DebugVariable helper class). Next we iterate forward starting at the first instruction in the BB. Whenever we find a dbg.value describing a DebugVariable (identified by {DILocalVariable, inlinedAt}) we save the {DIValue, DIExpression} that describes that variables value. But if the variable already was mapped to the same {DIValue, DIExpression} pair we instead drop the second dbg.value. To ease the process of making lit tests for this utility a new pass is introduced called RedundantDbgInstElimination. It can be executed by opt using -redundant-dbg-inst-elim. Reviewers: aprantl, jmorse, vsk Subscribers: hiraditya, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D71478
2019-12-13 03:51:13 +08:00
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -S -redundant-dbg-inst-elim | FileCheck %s
; All dbg.value with location "!dbg !19" are redundant in the input.
; FIXME: We do not handle non-overlapping/overlapping fragments perfectly yet.
define dso_local i16 @main(i16 %a1, i16 %a2) local_unnamed_addr #0 !dbg !7 {
; CHECK-LABEL: @main(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[BB0:%.*]]
; CHECK: bb0:
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 13, metadata !13, metadata !DIExpression()), !dbg !16
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 14, metadata !14, metadata !DIExpression()), !dbg !18
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 13, metadata !13, metadata !DIExpression()), !dbg !18
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 12, metadata !12, metadata !DIExpression()), !dbg !18
; CHECK-NEXT: br label [[BB1:%.*]]
; CHECK: bb1:
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[A1:%.*]], metadata !14, metadata !DIExpression()), !dbg !18
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 888, metadata !13, metadata !DIExpression()), !dbg !18
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[A2:%.*]], metadata !12, metadata !DIExpression()), !dbg !18
; CHECK-NEXT: [[T1:%.*]] = call i16 @bar(i16 0)
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[T1]], metadata !13, metadata !DIExpression()), !dbg !18
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[A2]], metadata !12, metadata !DIExpression(DW_OP_constu, 2, DW_OP_shr, DW_OP_stack_value)), !dbg !18
; CHECK-NEXT: br label [[BB2:%.*]]
; CHECK: bb2:
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[A1]], metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !18
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[A1]], metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 8, 8)), !dbg !18
; CHECK-NEXT: [[T2:%.*]] = call i16 @bar(i16 [[T1]])
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[T2]], metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !18
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[A1]], metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 8, 8)), !dbg !19
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb3:
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[A1]], metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !19
; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[A1]], metadata !13, metadata !DIExpression()), !dbg !18
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret i16 [[T2]]
;
entry:
br label %bb0
bb0:
call void @llvm.dbg.value(metadata i16 999, metadata !12, metadata !DIExpression()), !dbg !19
call void @llvm.dbg.value(metadata i16 996, metadata !13, metadata !DIExpression()), !dbg !19
call void @llvm.dbg.value(metadata i16 13, metadata !13, metadata !DIExpression()), !dbg !17
call void @llvm.dbg.value(metadata i16 998, metadata !12, metadata !DIExpression(DW_OP_constu, 2, DW_OP_shr, DW_OP_stack_value)), !dbg !19
call void @llvm.dbg.value(metadata i16 14, metadata !14, metadata !DIExpression()), !dbg !16
call void @llvm.dbg.value(metadata i16 997, metadata !12, metadata !DIExpression()), !dbg !19
call void @llvm.dbg.value(metadata i16 13, metadata !13, metadata !DIExpression()), !dbg !16
call void @llvm.dbg.value(metadata i16 12, metadata !12, metadata !DIExpression()), !dbg !16
br label %bb1
bb1:
call void @llvm.dbg.value(metadata i16 %a1, metadata !14, metadata !DIExpression()), !dbg !16
call void @llvm.dbg.value(metadata i16 888, metadata !13, metadata !DIExpression()), !dbg !16
call void @llvm.dbg.value(metadata i16 %a2, metadata !12, metadata !DIExpression()), !dbg !16
%t1 = call i16 @bar(i16 0)
call void @llvm.dbg.value(metadata i16 %a1, metadata !14, metadata !DIExpression()), !dbg !19
call void @llvm.dbg.value(metadata i16 %t1, metadata !13, metadata !DIExpression()), !dbg !16
call void @llvm.dbg.value(metadata i16 %a2, metadata !12, metadata !DIExpression(DW_OP_constu, 2, DW_OP_shr, DW_OP_stack_value)), !dbg !16
br label %bb2
bb2:
call void @llvm.dbg.value(metadata i16 %a1, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !19
call void @llvm.dbg.value(metadata i16 %a1, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 8, 8)), !dbg !19
call void @llvm.dbg.value(metadata i16 %a1, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !16
call void @llvm.dbg.value(metadata i16 %a1, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 8, 8)), !dbg !16
%t2 = call i16 @bar(i16 %t1)
call void @llvm.dbg.value(metadata i16 %t2, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !16
call void @llvm.dbg.value(metadata i16 %a1, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 8, 8)), !dbg !19
br label %bb3
bb3:
call void @llvm.dbg.value(metadata i16 %a1, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !19
call void @llvm.dbg.value(metadata i16 %a1, metadata !13, metadata !DIExpression()), !dbg !16
br label %exit
exit:
ret i16 %t2
}
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
declare i16 @bar(i16) #2
attributes #0 = { noinline nounwind }
attributes #1 = { nounwind readnone speculatable willreturn }
attributes #2 = { noinline nounwind readnone }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5}
!llvm.ident = !{!6}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !2, nameTableKind: None)
!1 = !DIFile(filename: "foo.c", directory: "")
!2 = !{}
!3 = !{i32 7, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"wchar_size", i32 1}
!6 = !{!"clang version 10.0.0"}
!7 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 8, type: !8, scopeLine: 8, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
!8 = !DISubroutineType(types: !9)
!9 = !{!10}
!10 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
!11 = !{!12, !13, !14}
!12 = !DILocalVariable(name: "x", scope: !7, file: !1, line: 9, type: !10)
!13 = !DILocalVariable(name: "y", scope: !7, file: !1, line: 10, type: !10)
!14 = !DILocalVariable(name: "u", scope: !15, file: !1, line: 11, type: !10)
!15 = distinct !DILexicalBlock(scope: !7, file: !1, line: 11, column: 3)
!16 = !DILocation(line: 0, scope: !7)
!17 = !DILocation(line: 0, scope: !7, inlinedAt: !18)
!18 = !DILocation(line: 1, scope: !7)
!19 = !DILocation(line: 77, scope: !7)