Index: llvm/include/llvm/Analysis/ScalarEvolution.h
===================================================================
--- llvm/include/llvm/Analysis/ScalarEvolution.h
+++ llvm/include/llvm/Analysis/ScalarEvolution.h
@@ -1204,6 +1204,9 @@
   /// to be infinite, it must also be undefined.
   bool loopIsFiniteByAssumption(const Loop *L);
 
+  /// Return an existing SCEV for V if there is one, otherwise return nullptr.
+  const SCEV *getExistingSCEV(Value *V);
+
 private:
   /// A CallbackVH to arrange for ScalarEvolution to be notified whenever a
   /// Value is deleted.
@@ -1944,9 +1947,6 @@
   /// Helper for forgetMemoizedResults.
   void forgetMemoizedResultsImpl(const SCEV *S);
 
-  /// Return an existing SCEV for V if there is one, otherwise return nullptr.
-  const SCEV *getExistingSCEV(Value *V);
-
   /// Erase Value from ValueExprMap and ExprValueMap.
   void eraseValueFromMap(Value *V);
 
Index: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -6500,7 +6500,11 @@
           if (!SE.isSCEVable(LocOp->getType()))
             return false;
 
-          const SCEV *S = SE.getSCEV(LocOp);
+          auto S = SE.getExistingSCEV(LocOp);
+          if (!S) {
+            S = SE.getSCEV(LocOp);
+            SE.forgetValue(LocOp);
+          }
           if (SE.containsUndefs(S))
             return false;
         }
@@ -6517,7 +6521,12 @@
       // during the salvage.
       NewRec->RecoveryExprs.resize(DVI->getNumVariableLocationOps());
       for (const auto LocOp : DVI->location_ops()) {
-        NewRec->SCEVs.push_back(SE.getSCEV(LocOp));
+        auto LocOpSCEV = SE.getExistingSCEV(LocOp);
+        if (!LocOpSCEV) {
+          LocOpSCEV = SE.getSCEV(LocOp);
+          SE.forgetValue(LocOp);
+        }
+        NewRec->SCEVs.push_back(LocOpSCEV);
         NewRec->LocationOps.push_back(LocOp);
         NewRec->HadLocationArgList = DVI->hasArgList();
       }
Index: llvm/test/Transforms/LoopStrengthReduce/dbg-inv-0.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopStrengthReduce/dbg-inv-0.ll
@@ -0,0 +1,72 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -loop-reduce -S | opt -S -strip-debug | FileCheck %s
+; RUN: opt < %s -strip-debug -S | opt -S -loop-reduce | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+; Verify that transformation is debug invariant. More specifically problems
+; were observed where SCEV had cached expressions during debug salvage analysis
+; (which only happens in presence of debug intrinsics) and then during
+; SCEVExpand these cached results were found and reused instead of new
+; instructions being generated for the transformed loop.
+
+define void @k(ptr %f) {
+; CHECK-LABEL: @k(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[F:%.*]], align 1
+; CHECK-NEXT:    [[INC:%.*]] = add nsw i32 [[TMP0]], 1
+; CHECK-NEXT:    store i32 [[INC]], ptr [[F]], align 1
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP:%.*]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[TMP0]], 1
+; CHECK-NEXT:    br label [[FOR_BODY3:%.*]]
+; CHECK:       for.body3:
+; CHECK-NEXT:    [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[FOR_BODY3]] ], [ [[TMP1]], [[FOR_COND_CLEANUP]] ]
+; CHECK-NEXT:    store i32 [[LSR_IV]], ptr null, align 1
+; CHECK-NEXT:    [[LSR_IV_NEXT]] = add i32 [[LSR_IV]], 1
+; CHECK-NEXT:    br label [[FOR_BODY3]]
+;
+entry:
+  %0 = load i32, ptr %f, align 1
+  %inc = add nsw i32 %0, 1
+  store i32 %inc, ptr %f, align 1
+  br label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %entry
+  br label %for.body3
+
+for.body3:                                        ; preds = %for.body3, %for.cond.cleanup
+  %1 = phi i32 [ %0, %for.cond.cleanup ], [ %inc4, %for.body3 ]
+  %inc4 = add nsw i32 %1, 1
+  store i32 %inc4, ptr null, align 1
+  call void @llvm.dbg.value(metadata i32 %inc, metadata !7, metadata !DIExpression(DW_OP_LLVM_convert, 32, DW_ATE_unsigned, DW_OP_LLVM_convert, 16, DW_ATE_unsigned, DW_OP_stack_value)), !dbg !18
+  br label %for.body3
+}
+
+; Function Attrs: nocallback nofree nosync nounwind readnone speculatable willreturn
+declare void @llvm.dbg.value(metadata, metadata, metadata) #0
+
+attributes #0 = { nocallback nofree nosync nounwind readnone speculatable willreturn }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "foo.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 7, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 1}
+!6 = !{i32 7, !"frame-pointer", i32 2}
+!7 = !DILocalVariable(name: "m", scope: !8, file: !1, line: 12, type: !15)
+!8 = distinct !DISubprogram(name: "k", scope: !1, file: !1, line: 7, type: !9, scopeLine: 7, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
+!9 = !DISubroutineType(types: !10)
+!10 = !{null}
+!11 = !{!12, !7, !16}
+!12 = !DILocalVariable(name: "l", scope: !13, file: !1, line: 10, type: !14)
+!13 = distinct !DILexicalBlock(scope: !8, file: !1, line: 10, column: 3)
+!14 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !15)
+!15 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
+!16 = !DILocalVariable(name: "n", scope: !17, file: !1, line: 13, type: !15)
+!17 = distinct !DILexicalBlock(scope: !8, file: !1, line: 13, column: 3)
+!18 = !DILocation(line: 0, scope: !8)