host-utils: Add muldiv64_round_up

This will be used for converting time intervals in different base units
to host units, for the purpose of scheduling timers to emulate target
timers. Timers typically must not fire before their requested expiry
time but may fire some time afterward, so rounding up is the right way
to implement these.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
[ clg: renamed __muldiv64() to muldiv64_rounding() ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>

diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 011618373e598ff9f47b8550ed219fdf66194386..ead97d354d6a2b45690b39560b1561853d226218 100644 (file)
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -56,6 +56,11 @@ static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
     return (__int128_t)a * b / c;
 }
 
+static inline uint64_t muldiv64_round_up(uint64_t a, uint32_t b, uint32_t c)
+{
+    return ((__int128_t)a * b + c - 1) / c;
+}
+
 static inline uint64_t divu128(uint64_t *plow, uint64_t *phigh,
                                uint64_t divisor)
 {
@@ -83,7 +88,8 @@ void mulu64(uint64_t *plow, uint64_t *phigh, uint64_t a, uint64_t b);
 uint64_t divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor);
 int64_t divs128(uint64_t *plow, int64_t *phigh, int64_t divisor);
 
-static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
+static inline uint64_t muldiv64_rounding(uint64_t a, uint32_t b, uint32_t c,
+                                  bool round_up)
 {
     union {
         uint64_t ll;
@@ -99,12 +105,25 @@ static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
 
     u.ll = a;
     rl = (uint64_t)u.l.low * (uint64_t)b;
+    if (round_up) {
+        rl += c - 1;
+    }
     rh = (uint64_t)u.l.high * (uint64_t)b;
     rh += (rl >> 32);
     res.l.high = rh / c;
     res.l.low = (((rh % c) << 32) + (rl & 0xffffffff)) / c;
     return res.ll;
 }
+
+static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
+{
+    return muldiv64_rounding(a, b, c, false);
+}
+
+static inline uint64_t muldiv64_round_up(uint64_t a, uint32_t b, uint32_t c)
+{
+    return muldiv64_rounding(a, b, c, true);
+}
 #endif
 
 /**