Various places in GCC use negate, bit-and and compare to test whether
an integer is a power of 2, but I think it would be clearer for this
test to be wrapped in a function.
OK for trunk?
commit e2ca9914ce46d56775854f50c21506b220fd50b6
Author: Jason Merrill <ja...@redhat.com>
Date: Wed Sep 7 16:22:32 2016 -0400
* hwint.h (pow2p_hwi): New.
diff --git a/gcc/hwint.h b/gcc/hwint.h
index 6b4d537..3d85fc3 100644
--- a/gcc/hwint.h
+++ b/gcc/hwint.h
@@ -299,4 +299,12 @@ absu_hwi (HOST_WIDE_INT x)
return x >= 0 ? (unsigned HOST_WIDE_INT)x : -(unsigned HOST_WIDE_INT)x;
}
+/* True if X is a power of two. */
+
+inline bool
+pow2p_hwi (unsigned HOST_WIDE_INT x)
+{
+ return (x & -x) == x;
+}
+
#endif /* ! GCC_HWINT_H */
