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authorClaudio Fontana <claudio.fontana@linaro.org>2013-11-27 17:27:04 +0100
committerPeter Maydell <peter.maydell@linaro.org>2013-12-06 17:24:03 +0000
commitbae68070a2aacaef2739eb0c0aa756b31dbc829d (patch)
tree29d68ecb73bb3f0bb7bf08300abaad7d082c5109
parent0fbc1f4cd1ffbea221d4dbf2768456ba8e737cce (diff)
downloadqemu-arm-bae68070a2aacaef2739eb0c0aa756b31dbc829d.tar.gz
host-utils: add clrsb32/64 - count leading redundant sign bits
this patch introduces wrappers for the clrsb builtins, which count the leading redundant sign bits. Signed-off-by: Claudio Fontana <claudio.fontana@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net>
-rw-r--r--include/qemu/host-utils.h32
1 files changed, 32 insertions, 0 deletions
diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 0f688c1c00..de85d282d0 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
*/