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[LoopUnroll] Remove redundant debug instructions after blocks have been merged #91246

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May 13, 2024
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[LoopUnroll] Remove redundant debug instructions after blocks have been merged #91246

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4 changes: 4 additions & 0 deletions llvm/lib/Transforms/Utils/LoopUnroll.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -377,6 +377,10 @@ void llvm::simplifyLoopAfterUnroll(Loop *L, bool SimplifyIVs, LoopInfo *LI,
const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
SmallVector<WeakTrackingVH, 16> DeadInsts;
for (BasicBlock *BB : L->getBlocks()) {
// Remove repeated debug instructions after loop unrolling.
if (BB->getParent()->getSubprogram())
RemoveRedundantDbgInstrs(BB);

for (Instruction &Inst : llvm::make_early_inc_range(*BB)) {
if (Value *V = simplifyInstruction(&Inst, {DL, nullptr, DT, AC}))
if (LI->replacementPreservesLCSSAForm(&Inst, V))
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50 changes: 50 additions & 0 deletions llvm/test/Transforms/LoopUnroll/unroll-remove-redundant-dbg.ll
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@@ -0,0 +1,50 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -S -passes=loop-unroll | FileCheck %s
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use llvm/utils/update_test_checks.py

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this isn't properly using update_test_checks.py, see the comments in that file. I believe the CHECK lines below need to be removed first. as the comments in update_test_checks.py say, please verify that there is a difference in IR with and without the loop unroll cleanup change

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Thanks, I use update_test_checks.py to generate CHECKs, and keep some important contents

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you shouldn't manually adjust CHECK lines generated by update_test_checks.py, just keep whatever it generates

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Thanks, keep all the CHECK lines.


define i64 @d(i1 %tobool.not, i32 %add, i64 %conv23) !dbg !14{
; There should be only one "llvm.dbg.vale" after loop unrolling
; CHECK-LABEL: @d(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: tail call void @llvm.dbg.value(metadata i32 0, metadata [[META16:![0-9]+]], metadata !DIExpression()), !dbg [[DBG17:![0-9]+]]
; CHECK-NEXT: ret i64 5
;
entry:
br label %for.body

for.body: ; preds = %for.body, %entry
%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)
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