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[BasicBlockUtils] Remove redundant llvm.dbg instructions after blocks to reduce compile time #89069

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Merged
merged 1 commit into from
Apr 26, 2024
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[BasicBlockUtils] Remove redundant llvm.dbg instructions after blocks to reduce compile time #89069

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4 changes: 4 additions & 0 deletions llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -333,6 +333,10 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, DomTreeUpdater *DTU,
// Finally, erase the old block and update dominator info.
DeleteDeadBlock(BB, DTU);

// Remove redundant "llvm.dbg" instrunctions after blocks have been merged.
if (PredBB->getParent()->getSubprogram())
RemoveRedundantDbgInstrs(PredBB);

return true;
}

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45 changes: 45 additions & 0 deletions llvm/test/Transforms/LoopUnroll/unroll-remove-redundant-dbg.ll
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@@ -0,0 +1,45 @@
; RUN: opt < %s -S -passes=loop-unroll | FileCheck %s

define i64 @d(i1 %tobool.not, i32 %add, i64 %conv23) !dbg !14{
entry:
br label %for.body

for.body: ; preds = %for.body, %entry
; There should be only one "llvm.dbg.vale" after loop unrolling
; CHECK: call void @llvm.dbg.value
; CHECK-NOT: call void @llvm.dbg.value

%k.045 = phi i64 [ 0, %entry ], [ %k.046, %for.body ]
tail call void @llvm.dbg.value(metadata i32 0, metadata !13, metadata !DIExpression()), !dbg !17
%k.046 = add nuw nsw i64 %k.045, 1
%exitcond = icmp ne i64 %k.046, 5
br i1 %exitcond, label %for.body, label %for.end22

for.end22: ; preds = %for.body
ret i64 %k.046
}

; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare void @llvm.dbg.value(metadata, metadata, metadata)

!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!12}

!0 = distinct !DICompileUnit(language: DW_LANG_C89, file: !1, producer: "clang version 19.0.0git (https://github.com/llvm/llvm-project.git ec062f5b33ed22c61742e3c1486f6cba915801e0)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !2, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "unroll-remove-redundant-dbg.c", directory: "", checksumkind: CSK_MD5, checksum: "aa30a1d8c04deb9b0f3885c258d2b674")
!2 = !{!3, !8, !10}
!3 = !DIGlobalVariableExpression(var: !4, expr: !DIExpression())
!4 = distinct !DIGlobalVariable(name: "a", scope: !0, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true)
!5 = !DIDerivedType(tag: DW_TAG_typedef, name: "uint32_t", file: !6, line: 198, baseType: !7)
!6 = !DIFile(filename: "/usr/include/stdint.h", directory: "", checksumkind: CSK_MD5, checksum: "da031bcff2d0c1d65aa92e7e68a44ef3")
!7 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
!8 = !DIGlobalVariableExpression(var: !9, expr: !DIExpression())
!9 = distinct !DIGlobalVariable(name: "c", scope: !0, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true)
!10 = !DIGlobalVariableExpression(var: !11, expr: !DIExpression())
!11 = distinct !DIGlobalVariable(name: "b", scope: !0, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true)
!12 = !{i32 2, !"Debug Info Version", i32 3}
!13 = !DILocalVariable(name: "f", scope: !14, file: !1, line: 4, type: !5)
!14 = distinct !DISubprogram(name: "d", scope: !1, file: !1, line: 3, type: !15, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !16)
!15 = !DISubroutineType(types: !16)
!16 = !{}
!17 = !DILocation(line: 0, scope: !14)
1 change: 0 additions & 1 deletion llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue-inlined.ll
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Expand Up @@ -9,7 +9,6 @@ init:

; CHECK: %vala = load i64, ptr %ptr
; CHECK-NEXT: call void @llvm.dbg.value(metadata i64 %vala, metadata [[MD:![0-9]*]]
; CHECK-NEXT: call void @llvm.dbg.value(metadata i64 %vala, metadata [[MD]]
; CHECK-NEXT: %valbmasked = and i64 %vala, 1

a: ; preds = %init
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1 change: 0 additions & 1 deletion llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue.ll
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Expand Up @@ -47,7 +47,6 @@ define i1 @hoist_with_debug2(i32 %x) !dbg !22 {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp ugt i32 [[X:%.*]], 2
; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[X]], metadata [[META21:![0-9]+]], metadata !DIExpression()), !dbg [[DBG23:![0-9]+]]
; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[X]], metadata [[META21]], metadata !DIExpression()), !dbg [[DBG23]]
; CHECK-NEXT: [[DOT:%.*]] = select i1 [[TOBOOL_NOT]], i1 false, i1 true
; CHECK-NEXT: ret i1 [[DOT]]
;
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