[llvm] 8763d79 - [loop-deletion] Overly defensive with undef-ing dbg.values.
Carlos Alberto Enciso via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 29 22:28:22 PDT 2023
Author: Carlos Alberto Enciso
Date: 2023-06-30T06:24:56+01:00
New Revision: 8763d79949975c7d2384c0311c66fa8e4a327c45
URL: https://github.com/llvm/llvm-project/commit/8763d79949975c7d2384c0311c66fa8e4a327c45
DIFF: https://github.com/llvm/llvm-project/commit/8763d79949975c7d2384c0311c66fa8e4a327c45.diff
LOG: [loop-deletion] Overly defensive with undef-ing dbg.values.
Explicitly inserting undef is overly defensive. Any values computed
nside the loop that are referenced by dbg.values should naturally
become undef when the loop is deleted, and all other values that
are loop invariant must be preserved.
Reviewed By: scott.linder
Differential Revision: https://reviews.llvm.org/D153539
Added:
llvm/test/Transforms/LoopDeletion/over-defensive-undefing-dbg-values.ll
Modified:
llvm/lib/Transforms/Utils/LoopUtils.cpp
llvm/test/DebugInfo/Generic/assignment-tracking/loop-deletion/dead-loop.ll
llvm/test/Transforms/LoopDeletion/diundef.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 2dfaea7e6680e6..7d6662c44f07a5 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -641,18 +641,17 @@ void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT, ScalarEvolution *SE,
}
// After the loop has been deleted all the values defined and modified
- // inside the loop are going to be unavailable.
- // Since debug values in the loop have been deleted, inserting an undef
- // dbg.value truncates the range of any dbg.value before the loop where the
- // loop used to be. This is particularly important for constant values.
+ // inside the loop are going to be unavailable. Values computed in the
+ // loop will have been deleted, automatically causing their debug uses
+ // be be replaced with undef. Loop invariant values will still be available.
+ // Move dbg.values out the loop so that earlier location ranges are still
+ // terminated and loop invariant assignments are preserved.
Instruction *InsertDbgValueBefore = ExitBlock->getFirstNonPHI();
assert(InsertDbgValueBefore &&
"There should be a non-PHI instruction in exit block, else these "
"instructions will have no parent.");
- for (auto *DVI : DeadDebugInst) {
- DVI->setKillLocation();
+ for (auto *DVI : DeadDebugInst)
DVI->moveBefore(InsertDbgValueBefore);
- }
}
// Remove the block from the reference counting scheme, so that we can
diff --git a/llvm/test/DebugInfo/Generic/assignment-tracking/loop-deletion/dead-loop.ll b/llvm/test/DebugInfo/Generic/assignment-tracking/loop-deletion/dead-loop.ll
index 6e0d093d276c4a..0e3a700246279b 100644
--- a/llvm/test/DebugInfo/Generic/assignment-tracking/loop-deletion/dead-loop.ll
+++ b/llvm/test/DebugInfo/Generic/assignment-tracking/loop-deletion/dead-loop.ll
@@ -18,7 +18,7 @@
;; mistake.
; CHECK: for.end:
-; CHECK-NEXT: call void @llvm.dbg.assign(metadata i32 poison,{{.+}}, metadata !DIExpression({{.+}}), metadata ![[ID:[0-9]+]], metadata ptr %Counter, metadata !DIExpression())
+; CHECK-NEXT: call void @llvm.dbg.assign(metadata i32 undef,{{.+}}, metadata !DIExpression({{.+}}), metadata ![[ID:[0-9]+]], metadata ptr %Counter, metadata !DIExpression())
; CHECK-NEXT: store i32 2, ptr %Counter, align 4,{{.*}}!DIAssignID ![[ID]]
define dso_local void @_Z3funv() local_unnamed_addr #0 !dbg !7 {
diff --git a/llvm/test/Transforms/LoopDeletion/diundef.ll b/llvm/test/Transforms/LoopDeletion/diundef.ll
index a721cd6eea85e0..14a6e401f9c6f1 100644
--- a/llvm/test/Transforms/LoopDeletion/diundef.ll
+++ b/llvm/test/Transforms/LoopDeletion/diundef.ll
@@ -18,7 +18,7 @@ for.cond: ; preds = %for.cond, %entry
%exitcond = icmp ne i32 %inc, 3, !dbg !23
br i1 %exitcond, label %for.cond, label %for.end, !dbg !24, !llvm.loop !25
-; CHECK: call void @llvm.dbg.value(metadata i32 poison, metadata !16, metadata !DIExpression()), !dbg !17
+; CHECK: call void @llvm.dbg.value(metadata i32 undef, metadata !16, metadata !DIExpression()), !dbg !17
; CHECK-NEXT: %call = tail call i32 {{.*}} @patatino()
for.end: ; preds = %for.cond
%call = tail call i32 (...) @patatino() #3, !dbg !27
diff --git a/llvm/test/Transforms/LoopDeletion/over-defensive-undefing-dbg-values.ll b/llvm/test/Transforms/LoopDeletion/over-defensive-undefing-dbg-values.ll
new file mode 100644
index 00000000000000..8eb1ef8ddd72a0
--- /dev/null
+++ b/llvm/test/Transforms/LoopDeletion/over-defensive-undefing-dbg-values.ll
@@ -0,0 +1,78 @@
+; RUN: opt -S %s -passes=loop-deletion | FileCheck %s
+
+;; static int foo(int Param) __attribute__((always_inline));
+;; static int foo(int Param) { return Param * Param * 2; }
+;;
+;; static int zero() __attribute__((always_inline));
+;; static int zero() { return 0; }
+;;
+;; void test() {
+;; int Constant = 0;
+;; for (int Index = zero(); Index < 0; ++Index) {
+;; foo(Index);
+;; Constant = 5;
+;; foo(Index + 1);
+;; }
+;; }
+;;
+;; Check that a loop invariant value in a dbg.value inside the dead
+;; loop is preserved.
+
+; CHECK-LABEL: for.end:
+; CHECK-NEXT: @llvm.dbg.value({{.+}} undef, metadata ![[VAR1:[0-9]+]],{{.+}}), !dbg ![[DBG1:[0-9]+]]
+; CHECK-NEXT: @llvm.dbg.value({{.+}} 5, metadata ![[VAR2:[0-9]+]],{{.+}}), !dbg ![[DBG2:[0-9]+]]
+
+; CHECK-DAG: ![[VAR1]] = !DILocalVariable(name: "Index"
+; CHECK-DAG: ![[VAR2]] = !DILocalVariable(name: "Constant"
+
+; CHECK-DAG: ![[DBG1]] = !DILocation(line: 0
+; CHECK-DAG: ![[DBG2]] = !DILocation(line: 0
+
+define dso_local void @test() !dbg !9 {
+entry:
+ call void @llvm.dbg.value(metadata i32 0, metadata !13, metadata !DIExpression()), !dbg !15
+ call void @llvm.dbg.value(metadata i32 0, metadata !16, metadata !DIExpression()), !dbg !18
+ br label %for.end, !dbg !19
+
+for.end: ; preds = %entry
+ call void @llvm.dbg.value(metadata i32 undef, metadata !16, metadata !DIExpression()), !dbg !18
+ call void @llvm.dbg.value(metadata i32 5, metadata !13, metadata !DIExpression()), !dbg !15
+ ret void, !dbg !30
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5, !6, !7}
+!llvm.ident = !{!8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 17.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test", directory: "", checksumkind: CSK_MD5, checksum: "53f7b620ca60e4fc7af4e6e4cdac8eea")
+!2 = !{i32 2, !"CodeView", i32 1}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 2}
+!5 = !{i32 8, !"PIC Level", i32 2}
+!6 = !{i32 7, !"uwtable", i32 2}
+!7 = !{i32 1, !"MaxTLSAlign", i32 65536}
+!8 = !{!"clang version 17.0.0"}
+!9 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 7, type: !10, scopeLine: 7, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !12)
+!10 = !DISubroutineType(types: !11)
+!11 = !{null}
+!12 = !{}
+!13 = !DILocalVariable(name: "Constant", scope: !9, file: !1, line: 8, type: !14)
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !DILocation(line: 0, scope: !9)
+!16 = !DILocalVariable(name: "Index", scope: !17, file: !1, line: 9, type: !14)
+!17 = distinct !DILexicalBlock(scope: !9, file: !1, line: 9)
+!18 = !DILocation(line: 0, scope: !17)
+!19 = !DILocation(line: 9, scope: !17)
+!21 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2, type: !22, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !0, retainedNodes: !12)
+!22 = !DISubroutineType(types: !23)
+!23 = !{!14, !14}
+!24 = !DILocation(line: 0, scope: !21, inlinedAt: !25)
+!25 = distinct !DILocation(line: 10, scope: !26)
+!26 = distinct !DILexicalBlock(scope: !27, file: !1, line: 9)
+!27 = distinct !DILexicalBlock(scope: !17, file: !1, line: 9)
+!28 = !DILocation(line: 0, scope: !21, inlinedAt: !29)
+!29 = distinct !DILocation(line: 12, scope: !26)
+!30 = !DILocation(line: 14, scope: !9)
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