[PATCH] utils: Use fma in qemu_strtosz

[Richard Henderson <richard.henderson@linaro.org>]

Use fma to simulatneously scale and round up fraction.

The libm function will always return a properly rounded double precision
value, which will eliminate any extra precision the x87 co-processor may
give us, which will keep the output predictable vs other hosts.

Adding DBL_EPSILON while scaling should help with fractions like
12.345, where the closest representable number is actually 12.3449*.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 util/cutils.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/util/cutils.c b/util/cutils.c
index d89a40a8c3..f7f8e48a68 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -342,7 +342,7 @@ static int do_strtosz(const char *nptr, const char **end,
         retval = -ERANGE;
         goto out;
     }
-    *result = val * mul + (uint64_t) (fraction * mul);
+    *result = val * mul + (uint64_t)fma(fraction, mul, DBL_EPSILON);
     retval = 0;
 
 out:
-- 
2.25.1