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authorbde <bde@FreeBSD.org>2008-02-22 11:59:05 +0000
committerbde <bde@FreeBSD.org>2008-02-22 11:59:05 +0000
commitd3a4e4141f36bdd5c9aaab68a7fb6cd09351b4ba (patch)
tree209838ded932502f665d35d819e1451dd3af5ddb /lib/msun/src
parent7ad2fb2ee1d49d8dc68037cbcdeaa7edc59bf2d2 (diff)
downloadFreeBSD-src-d3a4e4141f36bdd5c9aaab68a7fb6cd09351b4ba.zip
FreeBSD-src-d3a4e4141f36bdd5c9aaab68a7fb6cd09351b4ba.tar.gz
Optimize the conversion to bits a little (by about 11 cycles or 16%
on i386 (A64), 5 cycles on amd64 (A64), and 3 cycles on ia64). gcc tends to generate very bad code for accessing floating point values as bits except when the integer accesses have the same width as the floating point values, and direct accesses to bit-fields (as is common only for long double precision) always gives such accesses. Use the expsign access method, which is good for 80-bit long doubles and hopefully no worse for 128-bit long doubles. Now the generated code is less bad. There is still unnecessary copying of the arg on amd64 and i386 and mysterious extra slowness on amd64.
Diffstat (limited to 'lib/msun/src')
-rw-r--r--lib/msun/src/s_rintl.c18
1 files changed, 13 insertions, 5 deletions
diff --git a/lib/msun/src/s_rintl.c b/lib/msun/src/s_rintl.c
index 7f3b444e..b43df89 100644
--- a/lib/msun/src/s_rintl.c
+++ b/lib/msun/src/s_rintl.c
@@ -32,6 +32,11 @@ __FBSDID("$FreeBSD$");
#include "fpmath.h"
+#if LDBL_MAX_EXP != 0x4000
+/* We also require the usual bias, min exp and expsign packing. */
+#error "Unsupported long double format"
+#endif
+
#define BIAS (LDBL_MAX_EXP - 1)
static const float
@@ -50,16 +55,19 @@ long double
rintl(long double x)
{
union IEEEl2bits u;
- short sign;
+ uint32_t expsign;
+ int ex, sign;
u.e = x;
+ expsign = u.xbits.expsign;
+ ex = expsign & 0x7fff;
- if (u.bits.exp >= BIAS + LDBL_MANT_DIG - 1) {
- if (u.bits.exp == BIAS + LDBL_MAX_EXP)
+ if (ex >= BIAS + LDBL_MANT_DIG - 1) {
+ if (ex == BIAS + LDBL_MAX_EXP)
return (x + x); /* Inf, NaN, or unsupported format */
return (x); /* finite and already an integer */
}
- sign = u.bits.sign;
+ sign = expsign >> 15;
/*
* The following code assumes that intermediate results are
@@ -75,7 +83,7 @@ rintl(long double x)
* If the result is +-0, then it must have the same sign as x, but
* the above calculation doesn't always give this. Fix up the sign.
*/
- if (u.bits.exp < BIAS && x == 0.0L)
+ if (ex < BIAS && x == 0.0L)
return (zero[sign]);
return (x);
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