[llvm] 7964356 - [LoopUnroll] Remove redundant debug instructions after blocks have been merged (#91246)

[via llvm-commits]

Author: chenlin
Date: 2024-05-13T09:42:04-07:00
New Revision: 79643565a890d29560782fea23877ae61ea5b987

URL: https://github.com/llvm/llvm-project/commit/79643565a890d29560782fea23877ae61ea5b987
DIFF: https://github.com/llvm/llvm-project/commit/79643565a890d29560782fea23877ae61ea5b987.diff

LOG: [LoopUnroll] Remove redundant debug instructions after blocks have been merged (#91246)

Remove redundant debug instructions after blocks have been merged into
the predecessor, It can reduce some compile time in some cases.

This change only fixes the situation of loop unrolling, and other
situations are not considered. "RemoveRedundantDbgInstrs" seems to be
very time-consuming. Thus, we just add here after the "Dest" has been
merged into the "Fold", this may be a more targeted solution!!!

fixes: https://github.com/llvm/llvm-project/issues/89073

Added: 
    llvm/test/Transforms/LoopUnroll/unroll-remove-redundant-dbg.ll

Modified: 
    llvm/lib/Transforms/Utils/LoopUnroll.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 20978cf2e748a..1216538195fbd 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -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))

diff  --git a/llvm/test/Transforms/LoopUnroll/unroll-remove-redundant-dbg.ll b/llvm/test/Transforms/LoopUnroll/unroll-remove-redundant-dbg.ll
new file mode 100644
index 0000000000000..8e348281dc61c
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/unroll-remove-redundant-dbg.ll
@@ -0,0 +1,50 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -S -passes=loop-unroll | FileCheck %s
+
+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)