Index: include/llvm/Transforms/Utils/Local.h
===================================================================
--- include/llvm/Transforms/Utils/Local.h
+++ include/llvm/Transforms/Utils/Local.h
@@ -342,6 +342,11 @@
 /// Returns true if any debug users were updated.
 bool salvageDebugInfo(Instruction &I);
 
+/// Implementation of salvageDebugInfo, applying only to instructions in
+/// \p Insns, rather than all debug users of \p I.
+bool salvageDebugInfoForDbgValues(Instruction &I,
+                                  ArrayRef<DbgVariableIntrinsic *> Insns);
+
 /// Point debug users of \p From to \p To or salvage them. Use this function
 /// only when replacing all uses of \p From with \p To, with a guarantee that
 /// \p From is going to be deleted.
Index: lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- lib/Transforms/InstCombine/InstructionCombining.cpp
+++ lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3093,13 +3093,17 @@
   ++NumSunkInst;
 
   // Also sink all related debug uses from the source basic block. Otherwise we
-  // get debug use before the def.
-  SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
+  // get debug use before the def. Attempt to salvage debug uses first, as we
+  // don't wish to un-necessarily re-order variables.
+  SmallVector<DbgVariableIntrinsic *, 2> DbgUsers;
   findDbgUsers(DbgUsers, I);
   for (auto *DII : DbgUsers) {
     if (DII->getParent() == SrcBlock) {
-      DII->moveBefore(&*InsertPos);
-      LLVM_DEBUG(dbgs() << "SINK: " << *DII << '\n');
+      SmallVector<DbgVariableIntrinsic *, 1> TmpUser{DII};
+      if (!salvageDebugInfoForDbgValues(*I, TmpUser)) {
+        DII->moveBefore(&*InsertPos);
+        LLVM_DEBUG(dbgs() << "SINK: " << *DII << '\n');
+      }
     }
   }
   return true;
Index: lib/Transforms/Utils/Local.cpp
===================================================================
--- lib/Transforms/Utils/Local.cpp
+++ lib/Transforms/Utils/Local.cpp
@@ -1594,6 +1594,11 @@
   if (DbgUsers.empty())
     return false;
 
+  return salvageDebugInfoForDbgValues(I, DbgUsers);
+}
+
+bool llvm::salvageDebugInfoForDbgValues(
+    Instruction &I, ArrayRef<DbgVariableIntrinsic *> DbgUsers) {
   auto &M = *I.getModule();
   auto &DL = M.getDataLayout();
   auto &Ctx = I.getContext();
@@ -1643,10 +1648,13 @@
     // arithmetic to compute the variable's *value* in the DIExpression, we
     // need to mark the expression with a DW_OP_stack_value.
     APInt Offset(BitWidth, 0);
-    if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset))
+    if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) {
       for (auto *DII : DbgUsers)
         applyOffset(DII, Offset.getSExtValue());
-    return true;
+      return true;
+    } else {
+      return false;
+    }
   } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
     // Rewrite binary operations with constant integer operands.
     auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1));
Index: test/Transforms/InstCombine/debuginfo_add.ll
===================================================================
--- test/Transforms/InstCombine/debuginfo_add.ll
+++ test/Transforms/InstCombine/debuginfo_add.ll
@@ -22,6 +22,20 @@
 ; Function Attrs: nounwind ssp
 define void @f(%struct.vm_object* %object, i64* nocapture readonly %start) local_unnamed_addr #0 !dbg !11 {
 entry:
+
+  ; The 'load' and the 'add' are sunken out of this basic block. However it's
+  ; undesirable for the dbg.values to move: they can and should be salvaged.
+  ; Check that the middle dbg.value below is salvaged back to operating only
+  ; on %start rather than the sunk insts.
+  ;
+  ; CHECK-LABEL: entry:
+  ; CHECK:      call void @llvm.dbg.value(metadata i64* %start, metadata !22, metadata !DIExpression()), !dbg !
+  ; CHECK-NEXT: call void @llvm.dbg.value(metadata i64* %start, metadata !25, metadata !DIExpression(DW_OP_deref)), !dbg !
+  ; CHECK-NEXT: call void @llvm.dbg.value(metadata i64* %start, metadata !26, metadata !DIExpression(DW_OP_deref, DW_OP_constu, 4096, DW_OP_minus, DW_OP_stack_value)), !dbg !
+  ; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 undef, metadata !23, metadata !DIExpression()), !dbg !
+  ; CHECK-NEXT: br i1 undef
+
+
   tail call void @llvm.dbg.value(metadata %struct.vm_object* %object, metadata !21, metadata !DIExpression()), !dbg !27
   tail call void @llvm.dbg.value(metadata i64* %start, metadata !22, metadata !DIExpression()), !dbg !28
   %0 = load i64, i64* %start, align 4, !dbg !29
@@ -32,12 +46,11 @@
   br i1 undef, label %for.end, label %for.body.lr.ph, !dbg !32
 
 for.body.lr.ph:                                   ; preds = %entry
-  ; The 'load' and the 'add' are sunken to this basic block. So let's verify that the related dbg.values are sunken as well.
-  ; The add is later eliminated, so we verify that the dbg.value is salvaged by using DW_OP_minus.
+  ; Check that the load is sunk here; the add is optimised out. Nothing else
+  ; should be in this block.
   ; CHECK-LABEL: for.body.lr.ph:
   ; CHECK-NEXT: %0 = load
-  ; CHECK-NEXT: call void @llvm.dbg.value(metadata i64 %0, metadata !25, metadata !DIExpression()), !dbg !
-  ; CHECK-NEXT: call void @llvm.dbg.value(metadata i64 %0, metadata !26, metadata !DIExpression(DW_OP_constu, 4096, DW_OP_minus, DW_OP_stack_value)), !dbg !
+  ; CHECK-NEXT: br label %for.body
   br label %for.body, !dbg !32
 
 for.body:                                         ; preds = %for.body.lr.ph, %for.body