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Bug 551539 - use memcmp for inner loop of StringMatch, sometimes (r=bzbarsky)

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This commit is contained in:
Luke Wagner 2010-03-16 09:55:45 -07:00
parent 81068bf894
commit e133b17e2f
1 changed files with 74 additions and 41 deletions
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115
js/src/jsstr.cpp
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@ -1095,6 +1095,71 @@ js_BoyerMooreHorspool(const jschar *text, jsuint textlen,
return -1;
}
namespace {
struct MemCmp {
typedef jsuint Extent;
static JS_ALWAYS_INLINE Extent computeExtent(const jschar *, jsuint patlen) {
return (patlen - 1) * sizeof(jschar);
}
static JS_ALWAYS_INLINE bool match(const jschar *p, const jschar *t, Extent extent) {
return memcmp(p, t, extent) == 0;
}
};
struct ManualCmp {
typedef const jschar *Extent;
static JS_ALWAYS_INLINE Extent computeExtent(const jschar *pat, jsuint patlen) {
return pat + patlen;
}
static JS_ALWAYS_INLINE bool match(const jschar *p, const jschar *t, Extent extent) {
for (; p != extent; ++p, ++t) {
if (*p != *t)
return false;
}
return true;
}
};
}
template <class InnerMatch>
static jsint
Duff(const jschar *text, jsuint textlen, const jschar *pat, jsuint patlen)
{
JS_ASSERT(patlen > 1 && textlen > 0);
const jschar *textend = text + textlen - (patlen - 1);
const jschar p0 = *pat;
const jschar *const patNext = pat + 1;
const typename InnerMatch::Extent extent = InnerMatch::computeExtent(pat, patlen);
uint8 fixup;
const jschar *t = text;
switch ((textend - t) & 7) {
do {
case 0: if (*t++ == p0) { fixup = 8; goto match; }
case 7: if (*t++ == p0) { fixup = 7; goto match; }
case 6: if (*t++ == p0) { fixup = 6; goto match; }
case 5: if (*t++ == p0) { fixup = 5; goto match; }
case 4: if (*t++ == p0) { fixup = 4; goto match; }
case 3: if (*t++ == p0) { fixup = 3; goto match; }
case 2: if (*t++ == p0) { fixup = 2; goto match; }
case 1: if (*t++ == p0) { fixup = 1; goto match; }
continue;
do {
if (*t++ == p0) {
match:
if (!InnerMatch::match(patNext, t, extent))
goto failed_match;
return t - text - 1;
}
failed_match:;
} while (--fixup > 0);
} while(t != textend);
}
return -1;
}
static JS_ALWAYS_INLINE jsint
StringMatch(const jschar *text, jsuint textlen,
const jschar *pat, jsuint patlen)
@ -1138,50 +1203,18 @@ StringMatch(const jschar *text, jsuint textlen,
return index;
}
const jschar *textend = text + textlen - (patlen - 1);
const jschar *patend = pat + patlen;
const jschar p0 = *pat;
const jschar *patNext = pat + 1;
uint8 fixup;
#if __APPLE__ && __GNUC__ && __i386__
/*
* It is critical that |t| is kept in a register. The version of gcc we use
* to build on 32-bit Mac does not realize this. See bug 526173.
* For big patterns with large potential overlap we want the SIMD-optimized
* speed of memcmp. For small patterns, a simple loop is faster.
*
* FIXME: Linux memcmp performance is sad and the manual loop is faster.
*/
register const jschar *t asm("esi") = text;
#else
const jschar *t = text;
return
#if !defined(__linux__)
patlen > 128 ? Duff<MemCmp>(text, textlen, pat, patlen)
:
#endif
/* Credit: Duff */
switch ((textend - text) & 7) {
do {
case 0: if (*t++ == p0) { fixup = 8; goto match; }
case 7: if (*t++ == p0) { fixup = 7; goto match; }
case 6: if (*t++ == p0) { fixup = 6; goto match; }
case 5: if (*t++ == p0) { fixup = 5; goto match; }
case 4: if (*t++ == p0) { fixup = 4; goto match; }
case 3: if (*t++ == p0) { fixup = 3; goto match; }
case 2: if (*t++ == p0) { fixup = 2; goto match; }
case 1: if (*t++ == p0) { fixup = 1; goto match; }
continue;
do {
if (*t++ == p0) {
match:
for (const jschar *p1 = patNext, *t1 = t;
p1 != patend;
++p1, ++t1) {
if (*p1 != *t1)
goto failed_match;
}
return t - text - 1;
}
failed_match:;
} while (--fixup > 0);
} while(t != textend);
}
return -1;
Duff<ManualCmp>(text, textlen, pat, patlen);
}
static JSBool