[DebugInfo][SimplifyIndVar] Missing debug location updates for overflow/saturation instructions

[svs-quic]

Fixes #97986

[llvmbot]

@llvm/pr-subscribers-debuginfo

@llvm/pr-subscribers-llvm-transforms

Author: Sudharsan Veeravalli (svs-quic)

Changes

Fixes #97986

---

Full diff: https://github.com/llvm/llvm-project/pull/97987.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/Utils/SimplifyIndVar.cpp (+2)
• (added) llvm/test/Transforms/IndVarSimplify/preserving-debugloc-sat-overflow.ll (+103)

diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index e38505cbced34..5bda7c50c62c6 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -438,6 +438,7 @@ bool SimplifyIndvar::eliminateOverflowIntrinsic(WithOverflowInst *WO) {
       else {
         assert(EVI->getIndices()[0] == 0 && "Only two possibilities!");
         EVI->replaceAllUsesWith(NewResult);
+        NewResult->setDebugLoc(EVI->getDebugLoc());
       }
       ToDelete.push_back(EVI);
     }
@@ -467,6 +468,7 @@ bool SimplifyIndvar::eliminateSaturatingIntrinsic(SaturatingInst *SI) {
     BO->setHasNoUnsignedWrap();
 
   SI->replaceAllUsesWith(BO);
+  BO->setDebugLoc(SI->getDebugLoc());
   DeadInsts.emplace_back(SI);
   Changed = true;
   return true;
diff --git a/llvm/test/Transforms/IndVarSimplify/preserving-debugloc-sat-overflow.ll b/llvm/test/Transforms/IndVarSimplify/preserving-debugloc-sat-overflow.ll
new file mode 100644
index 0000000000000..f208c281e5fd0
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/preserving-debugloc-sat-overflow.ll
@@ -0,0 +1,103 @@
+; Test that the debug information is propagated correctly to the new instructions
+; RUN: opt < %s -passes=indvars -S | FileCheck %s
+
+; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
+declare i32 @llvm.uadd.sat.i32(i32, i32) #0
+
+; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
+declare { i32, i1 } @llvm.uadd.with.overflow.i32(i32, i32) #0
+
+define void @f_uadd(ptr %a) !dbg !5 {
+; CHECK-LABEL: define void @f_uadd(
+; CHECK:    [[TMP0:%.*]] = add nuw nsw i32 [[I_04:%.*]], 1, !dbg [[DBG14:![0-9]+]]
+;
+entry:
+  br label %for.body, !dbg !8
+
+for.cond.cleanup:                                 ; preds = %cont
+  ret void, !dbg !9
+
+for.body:                                         ; preds = %cont, %entry
+  %i.04 = phi i32 [ 0, %entry ], [ %2, %cont ], !dbg !10
+  %idxprom = sext i32 %i.04 to i64, !dbg !11
+  %arrayidx = getelementptr inbounds i8, ptr %a, i64 %idxprom, !dbg !12
+  store i8 0, ptr %arrayidx, align 1, !dbg !13
+  %0 = tail call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %i.04, i32 1), !dbg !14
+  %1 = extractvalue { i32, i1 } %0, 1, !dbg !15
+  br i1 %1, label %trap, label %cont, !dbg !16, !nosanitize !7
+
+trap:                                             ; preds = %for.body
+  tail call void @llvm.trap(), !dbg !17, !nosanitize !7
+  unreachable, !dbg !18, !nosanitize !7
+
+cont:                                             ; preds = %for.body
+  %2 = extractvalue { i32, i1 } %0, 0, !dbg !19
+  %cmp = icmp slt i32 %2, 16, !dbg !20
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !dbg !21
+}
+
+define void @uadd_sat(ptr %p) !dbg !22 {
+; CHECK-LABEL: define void @uadd_sat(
+; CHECK:    [[SAT1:%.*]] = add nuw nsw i32 [[I:%.*]], 1, !dbg [[DBG23:![0-9]+]]
+;
+entry:
+  br label %loop, !dbg !23
+
+loop:                                             ; preds = %loop, %entry
+  %i = phi i32 [ 0, %entry ], [ %i.inc, %loop ], !dbg !24
+  %sat = call i32 @llvm.uadd.sat.i32(i32 %i, i32 1), !dbg !25
+  store volatile i32 %sat, ptr %p, align 4, !dbg !26
+  %i.inc = add nuw nsw i32 %i, 1, !dbg !27
+  %cmp = icmp ne i32 %i.inc, 100, !dbg !28
+  br i1 %cmp, label %loop, label %end, !dbg !29
+
+end:                                              ; preds = %loop
+  ret void, !dbg !30
+}
+
+; Function Attrs: cold noreturn nounwind memory(inaccessiblemem: write)
+declare void @llvm.trap() #1
+
+attributes #0 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
+attributes #1 = { cold noreturn nounwind memory(inaccessiblemem: write) }
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+;.
+; CHECK: [[DBG14]] = !DILocation(line: 12,
+; CHECK: [[DBG23]] = !DILocation(line: 17,
+;.
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "eliminatesat.ll", directory: "/")
+!2 = !{i32 22}
+!3 = !{i32 0}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "f_uadd", linkageName: "f_uadd", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !DILocation(line: 1, column: 1, scope: !5)
+!9 = !DILocation(line: 2, column: 1, scope: !5)
+!10 = !DILocation(line: 3, column: 1, scope: !5)
+!11 = !DILocation(line: 4, column: 1, scope: !5)
+!12 = !DILocation(line: 5, column: 1, scope: !5)
+!13 = !DILocation(line: 6, column: 1, scope: !5)
+!14 = !DILocation(line: 7, column: 1, scope: !5)
+!15 = !DILocation(line: 8, column: 1, scope: !5)
+!16 = !DILocation(line: 9, column: 1, scope: !5)
+!17 = !DILocation(line: 10, column: 1, scope: !5)
+!18 = !DILocation(line: 11, column: 1, scope: !5)
+!19 = !DILocation(line: 12, column: 1, scope: !5)
+!20 = !DILocation(line: 13, column: 1, scope: !5)
+!21 = !DILocation(line: 14, column: 1, scope: !5)
+!22 = distinct !DISubprogram(name: "uadd_sat", linkageName: "uadd_sat", scope: null, file: !1, line: 15, type: !6, scopeLine: 15, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!23 = !DILocation(line: 15, column: 1, scope: !22)
+!24 = !DILocation(line: 16, column: 1, scope: !22)
+!25 = !DILocation(line: 17, column: 1, scope: !22)
+!26 = !DILocation(line: 18, column: 1, scope: !22)
+!27 = !DILocation(line: 19, column: 1, scope: !22)
+!28 = !DILocation(line: 20, column: 1, scope: !22)
+!29 = !DILocation(line: 21, column: 1, scope: !22)
+!30 = !DILocation(line: 22, column: 1, scope: !22)

[svs-quic]

@OCHyams @jryans could you please review this patch?

[jryans]

Seems reasonable to me, thanks! 😄

I'll aim to merge tomorrow if there's no other comments.

[OCHyams]

lgtm too 👍