[llvm] [GVN] Skip debug instructions in findDominatingValue function (PR #65977)
Sergey Kachkov via llvm-commits
llvm-commits at lists.llvm.org
Mon Sep 11 09:33:59 PDT 2023
https://github.com/skachkov-sc created https://github.com/llvm/llvm-project/pull/65977:
findDominatingValue has a search limit, and when it is reached, optimization is
not applied. This patch fixes the issue that this limit also takes into account
debug intrinsics, so the result of optimization can depend from the presence of
debug info.
>From 9241918024776e7b34f68d9244db8b287d7bc404 Mon Sep 17 00:00:00 2001
From: Sergey Kachkov <sergey.kachkov at syntacore.com>
Date: Mon, 11 Sep 2023 19:11:27 +0300
Subject: [PATCH 1/2] [GVN] Add pre-commit test
---
.../Transforms/GVN/load-through-select-dbg.ll | 46 +++++++++++++++++++
1 file changed, 46 insertions(+)
create mode 100644 llvm/test/Transforms/GVN/load-through-select-dbg.ll
diff --git a/llvm/test/Transforms/GVN/load-through-select-dbg.ll b/llvm/test/Transforms/GVN/load-through-select-dbg.ll
new file mode 100644
index 000000000000000..5789b1d2dbc2349
--- /dev/null
+++ b/llvm/test/Transforms/GVN/load-through-select-dbg.ll
@@ -0,0 +1,46 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt < %s -passes=gvn -gvn-max-num-visited-insts=4 -S | FileCheck %s
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+define i32 @foo(ptr %a, ptr %b) {
+; CHECK-LABEL: define i32 @foo(
+; CHECK-SAME: ptr [[A:%.*]], ptr [[B:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[A]], align 4
+; CHECK-NEXT: call void @llvm.dbg.declare(metadata ptr undef, metadata [[META4:![0-9]+]], metadata !DIExpression()), !dbg [[DBG14:![0-9]+]]
+; CHECK-NEXT: [[TMP1:%.*]] = load i32, ptr [[B]], align 4
+; CHECK-NEXT: [[COND:%.*]] = icmp slt i32 [[TMP0]], [[TMP1]]
+; CHECK-NEXT: [[PTR:%.*]] = select i1 [[COND]], ptr [[A]], ptr [[B]]
+; CHECK-NEXT: [[RES:%.*]] = load i32, ptr [[PTR]], align 4
+; CHECK-NEXT: ret i32 [[RES]]
+;
+entry:
+ %0 = load i32, ptr %a, align 4
+ call void @llvm.dbg.declare(metadata ptr undef, metadata !46, metadata !DIExpression()), !dbg !40
+ %1 = load i32, ptr %b, align 4
+ %cond = icmp slt i32 %0, %1
+ %ptr = select i1 %cond, ptr %a, ptr %b
+ %res = load i32, ptr %ptr, align 4
+ ret i32 %res
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!35, !36}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 17.0.0.prerel", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "bbi-78272.c", directory: "/tmp")
+!5 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
+
+!35 = !{i32 7, !"Dwarf Version", i32 4}
+!36 = !{i32 2, !"Debug Info Version", i32 3}
+!40 = !DILocation(line: 15, column: 7, scope: !41)
+!41 = distinct !DISubprogram(name: "x", scope: !1, file: !1, line: 14, type: !42, scopeLine: 14, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !45)
+!42 = !DISubroutineType(types: !43)
+!43 = !{!5}
+!45 = !{!46, !47, !48, !49, !50}
+!46 = !DILocalVariable(name: "t", scope: !41, file: !1, line: 15, type: !5)
+!47 = !DILocalVariable(name: "c", scope: !41, file: !1, line: 15, type: !5)
+!48 = !DILocalVariable(name: "v", scope: !41, file: !1, line: 15, type: !5)
+!49 = !DILocalVariable(name: "d", scope: !41, file: !1, line: 15, type: !5)
+!50 = !DILocalVariable(name: "u", scope: !41, file: !1, line: 16, type: !5)
>From 744d32d778c2323d5408c1f42a2a118aba33f776 Mon Sep 17 00:00:00 2001
From: Sergey Kachkov <sergey.kachkov at syntacore.com>
Date: Mon, 11 Sep 2023 19:05:27 +0300
Subject: [PATCH 2/2] [GVN] Skip debug instructions in findDominatingValue
function
findDominatingValue has a search limit, and when it is reached, optimization is
not applied. This patch fixes the issue that this limit also takes into account
debug intrinsics, so the result of optimization can depend from the presence of
debug info.
---
llvm/lib/Transforms/Scalar/GVN.cpp | 6 ++----
llvm/test/Transforms/GVN/load-through-select-dbg.ll | 4 ++--
2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index aaa757f48d08c4e..041591553499f63 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1147,13 +1147,11 @@ static Value *findDominatingValue(const MemoryLocation &Loc, Type *LoadTy,
BasicBlock *FromBB = From->getParent();
BatchAAResults BatchAA(*AA);
for (BasicBlock *BB = FromBB; BB; BB = BB->getSinglePredecessor())
- for (auto I = BB == FromBB ? From->getReverseIterator() : BB->rbegin(),
- E = BB->rend();
- I != E; ++I) {
+ for (auto *Inst = BB == FromBB ? From : BB->getTerminator();
+ Inst != nullptr; Inst = Inst->getPrevNonDebugInstruction()) {
// Stop the search if limit is reached.
if (++NumVisitedInsts > MaxNumVisitedInsts)
return nullptr;
- Instruction *Inst = &*I;
if (isModSet(BatchAA.getModRefInfo(Inst, Loc)))
return nullptr;
if (auto *LI = dyn_cast<LoadInst>(Inst))
diff --git a/llvm/test/Transforms/GVN/load-through-select-dbg.ll b/llvm/test/Transforms/GVN/load-through-select-dbg.ll
index 5789b1d2dbc2349..5d84c8549bb4c88 100644
--- a/llvm/test/Transforms/GVN/load-through-select-dbg.ll
+++ b/llvm/test/Transforms/GVN/load-through-select-dbg.ll
@@ -11,9 +11,9 @@ define i32 @foo(ptr %a, ptr %b) {
; CHECK-NEXT: call void @llvm.dbg.declare(metadata ptr undef, metadata [[META4:![0-9]+]], metadata !DIExpression()), !dbg [[DBG14:![0-9]+]]
; CHECK-NEXT: [[TMP1:%.*]] = load i32, ptr [[B]], align 4
; CHECK-NEXT: [[COND:%.*]] = icmp slt i32 [[TMP0]], [[TMP1]]
+; CHECK-NEXT: [[TMP2:%.*]] = select i1 [[COND]], i32 [[TMP0]], i32 [[TMP1]]
; CHECK-NEXT: [[PTR:%.*]] = select i1 [[COND]], ptr [[A]], ptr [[B]]
-; CHECK-NEXT: [[RES:%.*]] = load i32, ptr [[PTR]], align 4
-; CHECK-NEXT: ret i32 [[RES]]
+; CHECK-NEXT: ret i32 [[TMP2]]
;
entry:
%0 = load i32, ptr %a, align 4
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