diff --git a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
index c6962e51b2238..0bf90036b8b82 100644
--- a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
@@ -297,6 +297,10 @@ static void buildPartialInvariantUnswitchConditionalBranch(
   for (auto *Val : reverse(ToDuplicate)) {
     Instruction *Inst = cast<Instruction>(Val);
     Instruction *NewInst = Inst->clone();
+
+    if (const DebugLoc &DL = Inst->getDebugLoc())
+      mapAtomInstance(DL, VMap);
+
     NewInst->insertInto(&BB, BB.end());
     RemapInstruction(NewInst, VMap,
                      RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
diff --git a/llvm/test/DebugInfo/KeyInstructions/Generic/loop-unswitch.ll b/llvm/test/DebugInfo/KeyInstructions/Generic/loop-unswitch.ll
new file mode 100644
index 0000000000000..557950439ef3b
--- /dev/null
+++ b/llvm/test/DebugInfo/KeyInstructions/Generic/loop-unswitch.ll
@@ -0,0 +1,169 @@
+; RUN: opt %s -S --passes="loop-mssa(simple-loop-unswitch<nontrivial>)" -o - \
+; RUN: | FileCheck %s
+
+;; Unswitch from:
+;;                    +- noclobber -+
+;;                    |             v
+;; entry -> loop.header             loop.latch -> exit.
+;;          ^         |             ^        |
+;;          |         +- clobber ---+        |
+;;          +--------------------------------+
+;;
+;; To (unswitched loop unconditionally branches to noclobber.us):
+;;                          +---------------------------------------------+
+;;                          V                                             |
+;;     +- entry.split.us -> loop.header.us -> noclobber.us -> loop.latch.us -> exit.split.us -+
+;;     |                                                                                      |
+;; entry                                                                                      |
+;;     |                                                                                      v
+;;     +- entry.split -> loop.header -> noclobber -> loop.latch -> exit.split --------------> exit.
+;;                       ^         |                 ^        |
+;;                       |         +--> clobber -----+        |
+;;                       +------------------------------------+
+;;
+;; Check the duplicated instructions get remapped source atoms. Note some
+;; instructions get duplicated from loop.header into entry too.
+
+; CHECK-LABEL: define i32 @partial_unswitch_true_successor_hoist_invariant(
+; CHECK-SAME: ptr [[PTR:%.*]], i32 [[N:%.*]]) !dbg [[DBG5:![0-9]+]] {
+
+;; Instructions duplicated from loop.header need remapped atoms.
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr i32, ptr [[PTR]], i64 1, !dbg [[DBG8:![0-9]+]]
+; CHECK-NEXT:    [[TMP1:%.*]] = load i32, ptr [[TMP0]], align 4, !dbg [[DBG9:![0-9]+]]
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP1]], 100, !dbg [[DBG10:![0-9]+]]
+; CHECK-NEXT:    br i1 [[TMP2]], label %[[ENTRY_SPLIT_US:.*]], label %[[ENTRY_SPLIT:.*]]
+
+;; Same source location as entry's original br, with remapped atom group.
+; CHECK:       [[ENTRY_SPLIT_US]]:
+; CHECK-NEXT:    br label %[[LOOP_HEADER_US:.*]], !dbg [[DBG11:![0-9]+]]
+
+;; Instructions duplicated from loop.header need remapped atoms.
+; CHECK:       [[LOOP_HEADER_US]]:
+; CHECK-NEXT:    [[IV_US:%.*]] = phi i32 [ 0, %[[ENTRY_SPLIT_US]] ], [ [[IV_NEXT_US:%.*]], %[[LOOP_LATCH_US:.*]] ], !dbg [[DBG12:![0-9]+]]
+; CHECK-NEXT:    br label %[[NOCLOBBER_US:.*]], !dbg [[DBG13:![0-9]+]]
+
+;; Instructions duplicated from noclobber need remapped atoms.
+; CHECK:       [[NOCLOBBER_US]]:
+; CHECK-NEXT:    br label %[[LOOP_LATCH_US]], !dbg [[DBG14:![0-9]+]]
+
+; CHECK:       [[LOOP_LATCH_US]]:
+; CHECK-NEXT:    [[C_US:%.*]] = icmp ult i32 [[IV_US]], [[N]], !dbg [[DBG15:![0-9]+]]
+; CHECK-NEXT:    [[IV_NEXT_US]] = add i32 [[IV_US]], 1, !dbg [[DBG16:![0-9]+]]
+; CHECK-NEXT:    br i1 [[C_US]], label %[[LOOP_HEADER_US]], label %[[EXIT_SPLIT_US:.*]], !dbg [[DBG17:![0-9]+]]
+
+;; Split from exit, this DILocation shouldn't have source atom info.
+; CHECK:       [[EXIT_SPLIT_US]]:
+; CHECK-NEXT:    br label %[[EXIT:.*]], !dbg [[DBG18:![0-9]+]]
+
+;; Same source location as entry's original br, with remapped atom group.
+; CHECK:       [[ENTRY_SPLIT]]:
+; CHECK-NEXT:    br label %[[LOOP_HEADER:.*]], !dbg [[DBG19:![0-9]+]]
+
+;; Original loop blocks - the atoms groups should be distinct from those
+;; on duplicated instructions in the blocks above.
+; CHECK:       [[LOOP_HEADER]]:
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ 0, %[[ENTRY_SPLIT]] ], [ [[IV_NEXT:%.*]], %[[LOOP_LATCH:.*]] ], !dbg [[DBG20:![0-9]+]]
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i32, ptr [[PTR]], i64 1, !dbg [[DBG21:![0-9]+]]
+; CHECK-NEXT:    [[LV:%.*]] = load i32, ptr [[GEP]], align 4, !dbg [[DBG22:![0-9]+]]
+; CHECK-NEXT:    [[SC:%.*]] = icmp eq i32 [[LV]], 100, !dbg [[DBG23:![0-9]+]]
+; CHECK-NEXT:    br i1 [[SC]], label %[[NOCLOBBER:.*]], label %[[CLOBBER:.*]], !dbg [[DBG24:![0-9]+]]
+; CHECK:       [[NOCLOBBER]]:
+; CHECK-NEXT:    br label %[[LOOP_LATCH]], !dbg [[DBG25:![0-9]+]]
+; CHECK:       [[CLOBBER]]:
+; CHECK-NEXT:    call void @clobber(), !dbg [[DBG26:![0-9]+]]
+; CHECK-NEXT:    br label %[[LOOP_LATCH]], !dbg [[DBG27:![0-9]+]]
+; CHECK:       [[LOOP_LATCH]]:
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[IV]], [[N]], !dbg [[DBG28:![0-9]+]]
+; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1, !dbg [[DBG29:![0-9]+]]
+; CHECK-NEXT:    br i1 [[C]], label %[[LOOP_HEADER]], label %[[EXIT_SPLIT:.*]], !dbg [[DBG30:![0-9]+]]
+
+;; Split from exit, this DILocation shouldn't have source atom info.
+; CHECK:       [[EXIT_SPLIT]]:
+; CHECK-NEXT:    br label %[[EXIT]], !dbg [[DBG18]]
+
+;; exit.split and exit.split.us take the source location from here but drop its
+;; source atom info.
+; CHECK:       [[EXIT]]:
+; CHECK-NEXT:    ret i32 10, !dbg [[DBG33:![0-9]+]]
+
+define i32 @partial_unswitch_true_successor_hoist_invariant(ptr %ptr, i32 %N) !dbg !5 {
+entry:
+  br label %loop.header, !dbg !8
+
+loop.header:                                      ; preds = %loop.latch, %entry
+  %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop.latch ], !dbg !9
+  %gep = getelementptr i32, ptr %ptr, i64 1, !dbg !10
+  %lv = load i32, ptr %gep, align 4, !dbg !11
+  %sc = icmp eq i32 %lv, 100, !dbg !12
+  br i1 %sc, label %noclobber, label %clobber, !dbg !13
+
+noclobber:                                        ; preds = %loop.header
+  br label %loop.latch, !dbg !14
+
+clobber:                                          ; preds = %loop.header
+  call void @clobber(), !dbg !15
+  br label %loop.latch, !dbg !16
+
+loop.latch:                                       ; preds = %clobber, %noclobber
+  %c = icmp ult i32 %iv, %N, !dbg !17
+  %iv.next = add i32 %iv, 1, !dbg !18
+  br i1 %c, label %loop.header, label %exit, !dbg !19
+
+exit:                                             ; preds = %loop.latch
+  ret i32 10, !dbg !20
+}
+
+declare void @clobber()
+
+!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 13}
+!3 = !{i32 0}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "partial_unswitch_true_successor_hoist_invariant", linkageName: "partial_unswitch_true_successor_hoist_invariant", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !DILocation(line: 1, scope: !5, atomGroup: 1, atomRank: 1)
+!9 = !DILocation(line: 2, scope: !5, atomGroup: 2, atomRank: 1)
+!10 = !DILocation(line: 3, scope: !5, atomGroup: 3, atomRank: 1)
+!11 = !DILocation(line: 4, scope: !5, atomGroup: 4, atomRank: 1)
+!12 = !DILocation(line: 5, scope: !5, atomGroup: 5, atomRank: 1)
+!13 = !DILocation(line: 6, scope: !5, atomGroup: 6, atomRank: 1)
+!14 = !DILocation(line: 7, scope: !5, atomGroup: 7, atomRank: 1)
+!15 = !DILocation(line: 8, scope: !5, atomGroup: 8, atomRank: 1)
+!16 = !DILocation(line: 9, scope: !5, atomGroup: 9, atomRank: 1)
+!17 = !DILocation(line: 10, scope: !5, atomGroup: 10, atomRank: 1)
+!18 = !DILocation(line: 11, scope: !5, atomGroup: 11, atomRank: 1)
+!19 = !DILocation(line: 12, scope: !5, atomGroup: 12, atomRank: 1)
+!20 = !DILocation(line: 13, scope: !5, atomGroup: 13, atomRank: 1)
+;.
+; CHECK: [[DBG8]] = !DILocation(line: 3{{.*}}, atomGroup: 24, atomRank: 1)
+; CHECK: [[DBG9]] = !DILocation(line: 4{{.*}}, atomGroup: 25, atomRank: 1)
+; CHECK: [[DBG10]] = !DILocation(line: 5{{.*}}, atomGroup: 26, atomRank: 1)
+; CHECK: [[DBG11]] = !DILocation(line: 1{{.*}}, atomGroup: 14, atomRank: 1)
+; CHECK: [[DBG12]] = !DILocation(line: 2{{.*}}, atomGroup: 15, atomRank: 1)
+; CHECK: [[DBG13]] = !DILocation(line: 6{{.*}}, atomGroup: 19, atomRank: 1)
+; CHECK: [[DBG14]] = !DILocation(line: 7{{.*}}, atomGroup: 20, atomRank: 1)
+; CHECK: [[DBG15]] = !DILocation(line: 10{{.*}}, atomGroup: 21, atomRank: 1)
+; CHECK: [[DBG16]] = !DILocation(line: 11{{.*}}, atomGroup: 22, atomRank: 1)
+; CHECK: [[DBG17]] = !DILocation(line: 12{{.*}}, atomGroup: 23, atomRank: 1)
+; CHECK: [[DBG18]] = !DILocation(line: 13, scope: ![[#]])
+; CHECK: [[DBG19]] = !DILocation(line: 1{{.*}}, atomGroup: 1, atomRank: 1)
+; CHECK: [[DBG20]] = !DILocation(line: 2{{.*}}, atomGroup: 2, atomRank: 1)
+; CHECK: [[DBG21]] = !DILocation(line: 3{{.*}}, atomGroup: 3, atomRank: 1)
+; CHECK: [[DBG22]] = !DILocation(line: 4{{.*}}, atomGroup: 4, atomRank: 1)
+; CHECK: [[DBG23]] = !DILocation(line: 5{{.*}}, atomGroup: 5, atomRank: 1)
+; CHECK: [[DBG24]] = !DILocation(line: 6{{.*}}, atomGroup: 6, atomRank: 1)
+; CHECK: [[DBG25]] = !DILocation(line: 7{{.*}}, atomGroup: 7, atomRank: 1)
+; CHECK: [[DBG26]] = !DILocation(line: 8{{.*}}, atomGroup: 8, atomRank: 1)
+; CHECK: [[DBG27]] = !DILocation(line: 9{{.*}}, atomGroup: 9, atomRank: 1)
+; CHECK: [[DBG28]] = !DILocation(line: 10{{.*}}, atomGroup: 10, atomRank: 1)
+; CHECK: [[DBG29]] = !DILocation(line: 11{{.*}}, atomGroup: 11, atomRank: 1)
+; CHECK: [[DBG30]] = !DILocation(line: 12{{.*}}, atomGroup: 12, atomRank: 1)
+; CHECK: [[DBG33]] = !DILocation(line: 13{{.*}}, atomGroup: 13, atomRank: 1)
+;.