[CodeGen] Support native half inc/dec amounts.

We previously defaulted to long double, but it's also possible to have
a half inc/dec amount, when LangOpts NativeHalfType is set.
Currently, that's only true for OpenCL.

llvm-svn: 233135
diff --git a/clang/test/CodeGenOpenCL/half.cl b/clang/test/CodeGenOpenCL/half.cl
index 7ecae89..bd5ae7f 100644
--- a/clang/test/CodeGenOpenCL/half.cl
+++ b/clang/test/CodeGenOpenCL/half.cl
@@ -13,3 +13,11 @@
    return z;
 // CHECK: half 0xH3260
 }
+
+// CHECK-LABEL: @test_inc(half %x)
+// CHECK: [[INC:%.*]] = fadd half %x, 0xH3C00
+// CHECK: ret half [[INC]]
+half test_inc(half x)
+{
+  return ++x;
+}