(For X86) Enhancement to add-carray/sub-borrow (adc/sbb) optimization.

The adc/sbb optimization is to able to convert following expression
into a single adc/sbb instruction:
  (ult) ... = x + 1 // where the ult is unsigned-less-than comparison
  (ult) ... = x - 1

  This change is to flip the "x >u y" (i.e. ugt comparison) in order 
to expose the adc/sbb opportunity.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167180 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/X86/add-of-carry.ll

@@ -30,4 +30,17 @@ entry:
   ret i32 %z.0
 }
 
+; <rdar://problem/12579915>
+define i32 @test3(i32 %x, i32 %y, i32 %res) nounwind uwtable readnone ssp {
+entry:
+  %cmp = icmp ugt i32 %x, %y
+  %dec = sext i1 %cmp to i32
+  %dec.res = add nsw i32 %dec, %res
+  ret i32 %dec.res
+; CHECK: test3:
+; CHECK: cmpl
+; CHECK: sbbl
+; CHECK: ret
+}
+
 declare { i32, i1 } @llvm.uadd.with.overflow.i32(i32, i32) nounwind readnone