[KeyInstr][LoopRotate] Remap atoms of duplicated instructions (#133490)

RFC: https://discourse.llvm.org/t/rfc-improving-is-stmt-placement-for-better-interactive-debugging/82668

Author: OCHyams

llvm/lib/Transforms/Utils/LoopRotationUtils.cpp

@@ -657,6 +657,9 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
 
       // Otherwise, create a duplicate of the instruction.
       Instruction *C = Inst->clone();
+      if (const DebugLoc &DL = C->getDebugLoc())
+        mapAtomInstance(DL, ValueMap);
+
       C->insertBefore(LoopEntryBranch->getIterator());
 
       ++NumInstrsDuplicated;

llvm/test/DebugInfo/KeyInstructions/Generic/loop-rotate.ll

@@ -0,0 +1,74 @@
+; RUN: opt --passes=loop-rotate %s -S -o - | FileCheck %s
+
+;; Rotate:
+;;                +------------------> for.end.
+;;                |
+;;    entry -> for.cond -> for.body
+;;                ^           |
+;;                +-----------+
+;;
+;; Into:
+;;
+;;                               +------> for.end.
+;;                               |
+;;    entry (+ for.cond`0) -> for.body (+ for.cond) -+
+;;                               ^                   |
+;;                               +-------------------+
+;; Check for.cond's duplicated store and br have their source atoms remapped.
+
+; CHECK: entry:
+; CHECK:   store i32 0, ptr @glob, align 16, !dbg [[G3R1:![0-9]+]]
+; CHECK:   br label %for.body, !dbg [[G4R1:![0-9]+]]
+;
+; CHECK: for.body:
+; CHECK:    store i32 {{.*}}, ptr @glob, align 16, !dbg [[G1R1:![0-9]+]]
+; CHECK:    [[CMP:%.*]] = icmp slt i32 {{.*}}, 100, !dbg [[G2R2:![0-9]+]]
+; CHECK:    br i1 [[CMP]], label %for.body, label %for.end, !dbg [[G2R1:![0-9]+]]
+;
+; CHECK: [[G3R1]] = !DILocation(line: 4{{.*}}, atomGroup: 3, atomRank: 1)
+; CHECK: [[G4R1]] = !DILocation(line: 6{{.*}}, atomGroup: 4, atomRank: 1)
+; CHECK: [[G1R1]] = !DILocation(line: 4{{.*}}, atomGroup: 1, atomRank: 1)
+; CHECK: [[G2R2]] = !DILocation(line: 5{{.*}}, atomGroup: 2, atomRank: 2)
+; CHECK: [[G2R1]] = !DILocation(line: 6{{.*}}, atomGroup: 2, atomRank: 1)
+
+@glob = global i32 0
+
+define void @test1() #0 !dbg !5 {
+entry:
+  %array = alloca [20 x i32], align 16
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  store i32 %i.0, ptr @glob, align 16,         !dbg !DILocation(line: 4, scope: !5, atomGroup: 1, atomRank: 1)
+  %cmp = icmp slt i32 %i.0, 100,               !dbg !DILocation(line: 5, scope: !5, atomGroup: 2, atomRank: 2)
+  br i1 %cmp, label %for.body, label %for.end, !dbg !DILocation(line: 6, scope: !5, atomGroup: 2, atomRank: 1)
+
+for.body:                                         ; preds = %for.cond
+  %inc = add nsw i32 %i.0, 1
+  store i32 0, ptr %array, align 16
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  %arrayidx.lcssa = phi ptr [ %array, %for.cond ]
+  call void @g(ptr %arrayidx.lcssa)
+  ret void
+}
+
+declare void @g(ptr)
+
+attributes #0 = { nounwind ssp }
+attributes #1 = { noduplicate }
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "test.ll", directory: "/")
+!2 = !{i32 12}
+!3 = !{i32 0}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "test1", linkageName: "test1", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}