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[Qemu-devel] [PATCH] x86_64: optimise muldiv64 for x86_64 architecture
From: |
Frediano Ziglio |
Subject: |
[Qemu-devel] [PATCH] x86_64: optimise muldiv64 for x86_64 architecture |
Date: |
Fri, 9 Jan 2015 09:53:08 +0000 |
As this platform can do multiply/divide using 128 bit precision use
these instruction to implement it.
Signed-off-by: Frediano Ziglio <address@hidden>
---
include/qemu-common.h | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/include/qemu-common.h b/include/qemu-common.h
index f862214..5366220 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -370,6 +370,7 @@ static inline uint8_t from_bcd(uint8_t val)
}
/* compute with 96 bit intermediate result: (a*b)/c */
+#ifndef __x86_64__
static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
{
union {
@@ -392,6 +393,18 @@ static inline uint64_t muldiv64(uint64_t a, uint32_t b,
uint32_t c)
res.l.low = (((rh % c) << 32) + (rl & 0xffffffff)) / c;
return res.ll;
}
+#else
+static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
+{
+ uint64_t res;
+
+ asm ("mulq %2\n\tdivq %3"
+ : "=a"(res)
+ : "a"(a), "qm"((uint64_t) b), "qm"((uint64_t)c)
+ : "rdx", "cc");
+ return res;
+}
+#endif
/* Round number down to multiple */
#define QEMU_ALIGN_DOWN(n, m) ((n) / (m) * (m))
--
1.9.1
- [Qemu-devel] [PATCH] x86_64: optimise muldiv64 for x86_64 architecture,
Frediano Ziglio <=