[PATCH] [BUG] Fix regression after r214385

[Zinovy Nis]

Hi majnemer, bkramer,

r214385 fixed PR20189, but introduced a regression in cases where sub is used for immediates:

with r214385   


```
sub nsw %x, 123  ====> add %x, -123 
```

losing nsw/nuw attributes.

This patch fixes such a behavior for non-binary operations.

http://reviews.llvm.org/D5007

Files:
  lib/Transforms/InstCombine/InstCombineAddSub.cpp

Index: lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1539,6 +1539,10 @@
              "Expected a subtraction operator!");
       if (BO->hasNoSignedWrap() && I.hasNoSignedWrap())
         Res->setHasNoSignedWrap(true);
+    } else {
+      // Preserve nsw/nuw for non-binary operations.
+      Res->setHasNoSignedWrap(I.hasNoSignedWrap());
+      Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
     }
 
     return Res;
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