qemu-common.h: Move muldiv64() to host-utils.h

Move the muldiv64() function from qemu-common.h to host-utils.h.
This puts it together with all the other arithmetic functions
where we provide a version with __int128_t and a fallback
without, and allows headers which need muldiv64() to avoid
including qemu-common.h.

We don't include host-utils from qemu-common.h, to avoid dragging
more things into qemu-common.h than it already has; in practice
everywhere that needs muldiv64() can get it via qemu/timer.h.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>

2 files changed, 30 insertions, 0 deletions

diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index d4f21c9..c27d3dc 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -45,6 +45,12 @@ static inline void muls64(uint64_t *plow, uint64_t *phigh,
     *phigh = r >> 64;
 }
 
+/* compute with 96 bit intermediate result: (a*b)/c */
+static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
+{
+    return (__int128_t)a * b / c;
+}
+
 static inline int divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor)
 {
     if (divisor == 0) {
@@ -75,6 +81,29 @@ void muls64(uint64_t *phigh, uint64_t *plow, int64_t a, int64_t b);
 void mulu64(uint64_t *phigh, uint64_t *plow, uint64_t a, uint64_t b);
 int divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor);
 int divs128(int64_t *plow, int64_t *phigh, int64_t divisor);
+
+static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
+{
+    union {
+        uint64_t ll;
+        struct {
+#ifdef HOST_WORDS_BIGENDIAN
+            uint32_t high, low;
+#else
+            uint32_t low, high;
+#endif
+        } l;
+    } u, res;
+    uint64_t rl, rh;
+
+    u.ll = a;
+    rl = (uint64_t)u.l.low * (uint64_t)b;
+    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;
+}
 #endif
 
 /**
diff --git a/include/qemu/timer.h b/include/qemu/timer.h
index 5923d60..9939246 100644
--- a/include/qemu/timer.h
+++ b/include/qemu/timer.h
@@ -4,6 +4,7 @@
 #include "qemu/typedefs.h"
 #include "qemu-common.h"
 #include "qemu/notify.h"
+#include "qemu/host-utils.h"
 
 #define NANOSECONDS_PER_SECOND 1000000000LL