Index: lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2392,7 +2392,7 @@
     // If there is overflow, the result must be true or false.
     // TODO: Can we assert there is no overflow because InstSimplify always
     // handles those cases?
-    if (!Overflow)
+    if (!Overflow && !isa<PHINode>(X))
       // icmp Pred (add nsw X, C2), C --> icmp Pred X, (C - C2)
       return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
   }
Index: test/Transforms/InstCombine/icmp-add.ll
===================================================================
--- test/Transforms/InstCombine/icmp-add.ll
+++ test/Transforms/InstCombine/icmp-add.ll
@@ -175,6 +175,25 @@
   ret i1 %cmp
 }
 
+; icmp Pred (add nsw X, C2), C  --> should not be optimized to icmp Pred X, (C - C2) when X is a PHI node.
+define void @slt_phi_node_add_nsw(i32 %a) {
+; CHECK-LABEL: @slt_phi_node_add_nsw(
+; CHECK:    [[CMP:%.*]] = icmp slt i32 %inc, 255
+;
+entry:
+  br label %do.body
+
+do.body:                        ; preds = %do.body, %entry
+  %myValue = phi i32 [ 0, %entry ], [ %inc, %do.body ]
+  %inc = add nuw nsw i32 %myValue, 1
+  %add = add nsw i32 %a, 1
+  %cmp = icmp slt i32 %inc, 255
+  br i1 %cmp, label %do.body, label %do.end
+
+do.end:
+  ret void;
+}
+
 ; The same fold should work with vectors.
 
 define <2 x i1> @slt_zero_add_nsw_splat_vec(<2 x i8> %a) {