[llvm] [BasicBlockUtils] Remove redundant llvm.dbg instructions after blocks to reduce compile time (PR #89069)
via llvm-commits
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Wed Apr 24 02:34:32 PDT 2024
https://github.com/coderchenlin updated https://github.com/llvm/llvm-project/pull/89069
>From f5ea905335854256821e9f42c331187cf1eb1509 Mon Sep 17 00:00:00 2001
From: coderchenlin <chenlin048830 at gmail.com>
Date: Wed, 17 Apr 2024 21:01:52 +0800
Subject: [PATCH] [BasicBlockUtils] Remove redundant llvm.dbg instructions
after blocks have been merged.
When compiling with the "-g" and enabling loop-unroll optimization, the
redundant "llvm.dbg" instructions sometimes will be generated. It has
a significant impact on compilation time in some cases.
Fixes #89073.
---
llvm/lib/Transforms/Utils/BasicBlockUtils.cpp | 4 ++
.../LoopUnroll/unroll-remove-redundant-dbg.ll | 48 +++++++++++++++++++
.../SimplifyCFG/hoist-dbgvalue-inlined.ll | 1 -
.../Transforms/SimplifyCFG/hoist-dbgvalue.ll | 1 -
4 files changed, 52 insertions(+), 2 deletions(-)
create mode 100644 llvm/test/Transforms/LoopUnroll/unroll-remove-redundant-dbg.ll
diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 5aa59acfa6df99..56e921f916fbb0 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -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;
}
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 00000000000000..1b98b84655efea
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/unroll-remove-redundant-dbg.ll
@@ -0,0 +1,48 @@
+; RUN: opt < %s -S -passes=loop-unroll | FileCheck %s
+
+define i64 @d(i1 %tobool.not, i32 %add, i64 %conv23) #0 {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ ; There should be only one "llvm.dbg.vale" after loop unrolling
+ ; CHECK: tail call void @llvm.dbg.value(metadata i32 0, metadata !13, metadata !DIExpression()), !dbg !17
+ ; CHECK: ret i64 5
+
+ %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) #1
+
+attributes #0 = { nounwind }
+attributes #1 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
+
+!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)
diff --git a/llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue-inlined.ll b/llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue-inlined.ll
index e00d1daf71de58..5af73e789f11ce 100644
--- a/llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue-inlined.ll
+++ b/llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue-inlined.ll
@@ -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
diff --git a/llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue.ll b/llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue.ll
index af7da45ec089cc..c5d723c4e3dd61 100644
--- a/llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue.ll
+++ b/llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue.ll
@@ -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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