Index: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1109,6 +1109,26 @@
   return true;
 }
 
+static bool couldBeExpensiveGEP(ArrayRef<const Value *> Indices) {
+  // We try to maintain that GEPs have either all constant offset or exactly
+  // one non-constant offset. If merging GEPs can break this, we do not merge.
+  bool FoundNonConst = false;
+  bool FoundNonZeroConst = false;
+  for (unsigned Idx = 0, Size = Indices.size(); Idx != Size; ++Idx) {
+    if (auto *C = dyn_cast<Constant>(Indices[Idx])) {
+      if (!C->isNullValue())
+        FoundNonZeroConst = true;
+    } else {
+      if (FoundNonConst)
+        return true;
+      FoundNonConst = true;
+    }
+    if (FoundNonConst && FoundNonZeroConst)
+      return true;
+  }
+  return false;
+}
+
 /// Return a value X such that Val = X * Scale, or null if none.
 /// If the multiplication is known not to overflow, then NoSignedWrap is set.
 Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) {
@@ -1778,10 +1798,17 @@
 
       // Update the GEP in place if possible.
       if (Src->getNumOperands() == 2) {
+        if (!Src->hasOneUse()) {
+          Indices.push_back(Sum);
+          Indices.append(GEP.op_begin() + 2, GEP.op_end());
+          if (couldBeExpensiveGEP(Indices))
+            return nullptr;
+        }
         GEP.setOperand(0, Src->getOperand(0));
         GEP.setOperand(1, Sum);
         return &GEP;
       }
+
       Indices.append(Src->op_begin()+1, Src->op_end()-1);
       Indices.push_back(Sum);
       Indices.append(GEP.op_begin()+2, GEP.op_end());
@@ -1793,7 +1820,10 @@
       Indices.append(GEP.idx_begin()+1, GEP.idx_end());
     }
 
-    if (!Indices.empty())
+    if (!Indices.empty()) {
+      if (!Src->hasOneUse() && couldBeExpensiveGEP(Indices))
+        return nullptr;
+
       return GEP.isInBounds() && Src->isInBounds()
                  ? GetElementPtrInst::CreateInBounds(
                        Src->getSourceElementType(), Src->getOperand(0), Indices,
@@ -1801,6 +1831,7 @@
                  : GetElementPtrInst::Create(Src->getSourceElementType(),
                                              Src->getOperand(0), Indices,
                                              GEP.getName());
+    }
   }
 
   if (GEP.getNumIndices() == 1) {
Index: llvm/test/Transforms/InstCombine/gepphigep.ll
===================================================================
--- llvm/test/Transforms/InstCombine/gepphigep.ll
+++ llvm/test/Transforms/InstCombine/gepphigep.ll
@@ -52,9 +52,9 @@
   ret i32 %tmp25
 
 ; CHECK-LABEL: @test2(
-; CHECK: getelementptr inbounds %struct2, %struct2* %tmp1, i64 %tmp9, i32 0
+; CHECK: getelementptr inbounds %struct2, %struct2* %tmp10, i64 0, i32 0
 ; CHECK: getelementptr inbounds %struct2, %struct2* %tmp1, i64 %tmp19, i32 0
-; CHECK: getelementptr inbounds %struct2, %struct2* %tmp1, i64 %tmp9, i32 1
+; CHECK: getelementptr inbounds %struct2, %struct2* %tmp10, i64 0, i32 1
 }
 
 ; Check that instcombine doesn't insert GEPs before landingpad.
Index: llvm/test/Transforms/InstCombine/unit_skip_gep_merge.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/unit_skip_gep_merge.ll
@@ -0,0 +1,28 @@
+; RUN: opt -instcombine -S < %s |  FileCheck %s
+
+%ST = type {i8*, i8*, i8*}
+declare void @bar(i8*)
+
+; CHECK-LABEL: @foo
+; CHECK-LABEL: entry
+; CHECK: %tmp1 = getelementptr inbounds %ST, %ST* %arrayidx8
+; CHECK-LABEL: BB0
+; CHECK: %tmp2 = getelementptr inbounds %ST, %ST* %arrayidx8
+define void @foo(%ST* %B, i1 %c, i64 %v, i8** %S, i8** %S2) {
+entry:
+  %arrayidx8 = getelementptr inbounds %ST, %ST* %B, i64 %v
+  %tmp1 = getelementptr inbounds %ST, %ST* %arrayidx8, i64 0, i32 1
+  %r = load i8*, i8** %tmp1
+  store i8* %r, i8** %S2
+  br i1 %c, label %BB0, label %BB2
+
+BB0:
+  %tmp2 = getelementptr inbounds %ST, %ST* %arrayidx8, i64 0, i32 2
+  %l = load i8*, i8** %tmp2
+  store i8* %l, i8** %S
+  br label %BB2
+
+BB2:
+  ret void
+}
+