From: Claudio Fontana <claudio.font...@linaro.org>
this patch introduces wrappers for the clrsb builtins,
which count the leading redundant sign bits.
Signed-off-by: Claudio Fontana <claudio.font...@linaro.org>
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
Reviewed-by: Richard Henderson <r...@twiddle.net>
---
include/qemu/host-utils.h | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 0f688c1..de85d28 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -228,6 +228,38 @@ static inline int cto64(uint64_t val)
}
/**
+ * clrsb32 - count leading redundant sign bits in a 32-bit value.
+ * @val: The value to search
+ *
+ * Returns the number of bits following the sign bit that are equal to it.
+ * No special cases; output range is [0-31].
+ */
+static inline int clrsb32(uint32_t val)
+{
+#if QEMU_GNUC_PREREQ(4, 7)
+ return __builtin_clrsb(val);
+#else
+ return clz32(val ^ ((int32_t)val >> 1)) - 1;
+#endif
+}
+
+/**
+ * clrsb64 - count leading redundant sign bits in a 64-bit value.
+ * @val: The value to search
+ *
+ * Returns the number of bits following the sign bit that are equal to it.
+ * No special cases; output range is [0-63].
+ */
+static inline int clrsb64(uint64_t val)
+{
+#if QEMU_GNUC_PREREQ(4, 7)
+ return __builtin_clrsbll(val);
+#else
+ return clz64(val ^ ((int64_t)val >> 1)) - 1;
+#endif
+}
+
+/**
* ctpop8 - count the population of one bits in an 8-bit value.
* @val: The value to search
*/
--
1.8.5
