diff options
| author | Anton Blanchard <anton@samba.org> | 2015-05-26 22:42:13 +1000 |
|---|---|---|
| committer | Remi Collet <remi@php.net> | 2015-07-28 18:38:23 +0200 |
| commit | 305199a13163e246b909ef32880df032823bff05 (patch) | |
| tree | a855e451319a524067c17d60bac3948d0fd96438 | |
| parent | a581910a76276a152dae1953fdf3b25d8c9a8f85 (diff) | |
| download | php-git-305199a13163e246b909ef32880df032823bff05.tar.gz | |
Improve performance of PowerPC64 ZEND_SIGNED_MULTIPLY_LONG
Detecting overflow with the XER is slow, partially because we have to
clear it before use. We can do better by using a trick where we compare
the high 64 bits of the result with the low 64 bits shifted right
63 bits.
This is 7% faster on a POWER8 running a simple testcase:
<?php
function testcase($count = 100000000) {
for ($i = 0; $i < $count; $i++) {
$x = 1;
$x = $x * 2;
$x = $x * 2;
$x = $x * 2;
$x = $x * 2;
}
}
testcase();
?>
| -rw-r--r-- | Zend/zend_multiply.h | 27 |
1 files changed, 13 insertions, 14 deletions
diff --git a/Zend/zend_multiply.h b/Zend/zend_multiply.h index b12c1e23b3..fc053d0e35 100644 --- a/Zend/zend_multiply.h +++ b/Zend/zend_multiply.h @@ -74,20 +74,19 @@ #elif defined(__powerpc64__) && defined(__GNUC__) -#define ZEND_SIGNED_MULTIPLY_LONG(a, b, lval, dval, usedval) do { \ - long __tmpvar; \ - __asm__("li 14, 0\n\t" \ - "mtxer 14\n\t" \ - "mulldo. %0, %2,%3\n\t" \ - "xor %1, %1, %1\n\t" \ - "bns+ 0f\n\t" \ - "li %1, 1\n\t" \ - "0:\n" \ - : "=r"(__tmpvar),"=r"(usedval) \ - : "r"(a), "r"(b) \ - : "r14", "cc"); \ - if (usedval) (dval) = (double) (a) * (double) (b); \ - else (lval) = __tmpvar; \ +#define ZEND_SIGNED_MULTIPLY_LONG(a, b, lval, dval, usedval) do { \ + long __low, __high; \ + __asm__("mulld %0,%2,%3\n\t" \ + "mulhd %1,%2,%3\n" \ + : "=&r"(__low), "=&r"(__high) \ + : "r"(a), "r"(b)); \ + if ((__low >> 63) != __high) { \ + (dval) = (double) (a) * (double) (b); \ + (usedval) = 1; \ + } else { \ + (lval) = __low; \ + (usedval) = 0; \ + } \ } while (0) #elif SIZEOF_ZEND_LONG == 4 |