[DebugInfo][LoopUnroll] Preserve DebugLocs on optimized cond branches #114225
Conversation
This patch fixes a simple error where as part of loop unrolling we optimize conditional loop-exiting branches into unconditional branches when we know that they will or won't exit the loop, but does not propagate the source location of the original branch to the new one.
SLTozer
requested review from
jmorse,
adrian-prantl,
OCHyams,
dwblaikie and
CarlosAlbertoEnciso
|
@llvm/pr-subscribers-llvm-transforms @llvm/pr-subscribers-debuginfo Author: Stephen Tozer (SLTozer) ChangesThis patch fixes a simple error where as part of loop unrolling we optimize conditional loop-exiting branches into unconditional branches when we know that they will or won't exit the loop, but does not propagate the source location of the original branch to the new one. Full diff: https://github.com/llvm/llvm-project/pull/114225.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index b90addcef69e6e..4cbbac07915fbe 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -883,7 +883,8 @@ llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
DeadSucc->removePredecessor(Src, /* KeepOneInputPHIs */ true);
// Replace the conditional branch with an unconditional one.
- BranchInst::Create(Dest, Term->getIterator());
+ auto *BI = BranchInst::Create(Dest, Term->getIterator());
+ BI->setDebugLoc(Term->getDebugLoc());
Term->eraseFromParent();
DTUpdates.emplace_back(DominatorTree::Delete, Src, DeadSucc);
diff --git a/llvm/test/Transforms/LoopUnroll/preserve-branch-debuglocs.ll b/llvm/test/Transforms/LoopUnroll/preserve-branch-debuglocs.ll
new file mode 100644
index 00000000000000..623fb68c784fe7
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/preserve-branch-debuglocs.ll
@@ -0,0 +1,52 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
+; RUN: opt < %s -passes=loop-unroll -S | FileCheck %s
+; RUN: opt < %s -passes=loop-unroll-full -S | FileCheck %s
+
+;; Loop Unrolling should preserve the DebugLocs of conditional branches that get
+;; optimized into unconditional branches.
+
+define i32 @_ZeqRK4int3S1_() {
+; CHECK-LABEL: define i32 @_ZeqRK4int3S1_() {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: br label %[[FOR_BODY:.*]]
+; CHECK: [[FOR_COND:.*]]:
+; CHECK-NEXT: br label %[[CLEANUP:.*]], !dbg [[DBG3:![0-9]+]]
+; CHECK: [[FOR_BODY]]:
+; CHECK-NEXT: br i1 false, label %[[FOR_COND]], label %[[CLEANUP]]
+; CHECK: [[CLEANUP]]:
+; CHECK-NEXT: ret i32 0
+;
+entry:
+ br label %for.body
+
+for.cond: ; preds = %for.body
+ br i1 false, label %cleanup, label %for.body, !dbg !3
+
+for.body: ; preds = %for.cond, %entry
+ br i1 false, label %for.cond, label %cleanup
+
+cleanup: ; preds = %for.body, %for.cond
+ ret i32 0
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 20.0.0git", isOptimized: true, runtimeVersion: 0, emissionKind: NoDebug)
+!1 = !DIFile(filename: "test.cpp", directory: "/tmp")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = !DILocation(line: 304, column: 2, scope: !4)
+!4 = distinct !DILexicalBlock(scope: !5, file: !1, line: 304, column: 2)
+!5 = distinct !DISubprogram(name: "operator==", linkageName: "_ZeqRK4int3S1_", scope: !1, file: !1, line: 302, type: !6, scopeLine: 303, spFlags: DISPFlagDefinition, unit: !0)
+!6 = distinct !DISubroutineType(types: !7)
+!7 = !{}
+;.
+; CHECK: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: [[META1:![0-9]+]], producer: "{{.*}}clang version {{.*}}", isOptimized: true, runtimeVersion: 0, emissionKind: NoDebug)
+; CHECK: [[META1]] = !DIFile(filename: "test.cpp", directory: {{.*}})
+; CHECK: [[META2:![0-9]+]] = !{i32 2, !"Debug Info Version", i32 3}
+; CHECK: [[DBG3]] = !DILocation(line: 304, column: 2, scope: [[META4:![0-9]+]])
+; CHECK: [[META4]] = distinct !DILexicalBlock(scope: [[META5:![0-9]+]], file: [[META1]], line: 304, column: 2)
+; CHECK: [[META5]] = distinct !DISubprogram(name: "operator==", linkageName: "_ZeqRK4int3S1_", scope: [[META1]], file: [[META1]], line: 302, type: [[META6:![0-9]+]], scopeLine: 303, spFlags: DISPFlagDefinition, unit: [[META0]])
+; CHECK: [[META6]] = distinct !DISubroutineType(types: [[META7:![0-9]+]])
+; CHECK: [[META7]] = !{}
+;.
|
Yes, do you have any suggestions for how to unobtrusively make the set of PRs more searchable? |
if you've got a PR or issue for the overarching thing, you can probably just mention that by number with #XXXX in each of these fixes to link back to the main thing - not the /most/ searchable thing (I don't know how to quickly then make a list of all the things that reference an issue) but at least they will be available in one page (the backlinks will create updates/be noted on the main issue - just not in a neat and tidy list, but in part of the update stream of comments, etc) |
Yeah, either mentioning some phrase (e.g. "DebugLoc coverage tracking") that you include in the description of all related PRs or linking to some top-level PR / issue should work. You can then search all PRs for "DebugLoc coverage" or "#XXXX" to produce a list. |
…llvm#114225) This patch fixes a simple error where as part of loop unrolling we optimize conditional loop-exiting branches into unconditional branches when we know that they will or won't exit the loop, but does not propagate the source location of the original branch to the new one. Found using llvm#107279.
This patch fixes a simple error where as part of loop unrolling we optimize conditional loop-exiting branches into unconditional branches when we know that they will or won't exit the loop, but does not propagate the source location of the original branch to the new one.
Found using #107279.