Make pow2ceil() and pow2floor() inline

Since the pow2floor() function is now used in a hot code path,
make it inline; for consistency, provide pow2ceil() as an inline
function too.

Because these functions use ctz64() we have to put the inline
versions into host-utils.h, so they have access to ctz64(),
and move the inline is_power_of_2() along with them.

We then need to include host-utils.h from qemu-common.h so that
the files which use these functions via qemu-common.h still have
access to them.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1437741192-20955-7-git-send-email-peter.maydell@linaro.org

1 files changed, 33 insertions, 0 deletions

diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index c27d3dc898..7d36ebfd5b 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -27,6 +27,7 @@
 
 #include "qemu/compiler.h"   /* QEMU_GNUC_PREREQ */
 #include <limits.h>
+#include <stdbool.h>
 
 #ifdef CONFIG_INT128
 static inline void mulu64(uint64_t *plow, uint64_t *phigh,
@@ -408,4 +409,36 @@ static inline int ctpop64(uint64_t val)
 # error Unknown sizeof long
 #endif
 
+static inline bool is_power_of_2(uint64_t value)
+{
+    if (!value) {
+        return 0;
+    }
+
+    return !(value & (value - 1));
+}
+
+/* round down to the nearest power of 2*/
+static inline int64_t pow2floor(int64_t value)
+{
+    if (!is_power_of_2(value)) {
+        value = 0x8000000000000000ULL >> clz64(value);
+    }
+    return value;
+}
+
+/* round up to the nearest power of 2 (0 if overflow) */
+static inline uint64_t pow2ceil(uint64_t value)
+{
+    uint8_t nlz = clz64(value);
+
+    if (is_power_of_2(value)) {
+        return value;
+    }
+    if (!nlz) {
+        return 0;
+    }
+    return 1ULL << (64 - nlz);
+}
+
 #endif