refs.c: SSE2 optimizations for check_refname_component

Optimize check_refname_component using SSE2 on x86_64.

git rev-parse HEAD is a good test-case for this, since it does almost
nothing except parse refs.  For one particular repo with about 60k
refs, almost all packed, the timings are:

Look up table: 29 ms
SSE2:          23 ms

This cuts about 20% off of the runtime.

Ondřej Bílka <neleai@seznam.cz> suggested an SSE2 approach to the
substring searches, which netted a speed boost over the SSE4.2 code I
had initially written.

Signed-off-by: David Turner <dturner@twitter.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
David Turner 2014-06-18 01:54:42 -04:00 коммит произвёл Junio C Hamano
Родитель dde8a902c7
Коммит 745224e04a
4 изменённых файлов: 250 добавлений и 18 удалений

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@ -677,6 +677,17 @@ void git_qsort(void *base, size_t nmemb, size_t size,
#endif
#endif
#if defined(__GNUC__) && defined(__x86_64__)
#include <emmintrin.h>
/*
* This is the system memory page size; it's used so that we can read
* outside the bounds of an allocation without segfaulting.
*/
#ifndef PAGE_SIZE
#define PAGE_SIZE 4096
#endif
#endif
#ifdef UNRELIABLE_FSTAT
#define fstat_is_reliable() 0
#else

234
refs.c
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@ -7,21 +7,27 @@
/*
* How to handle various characters in refnames:
* This table is used by both the SIMD and non-SIMD code. It has
* some cases that are only useful for the SIMD; these are handled
* equivalently to the listed disposition in the non-SIMD code.
* 0: An acceptable character for refs
* 1: End-of-component
* 2: ., look for a preceding . to reject .. in refs
* 3: {, look for a preceding @ to reject @{ in refs
* 4: A bad character: ASCII control characters, "~", "^", ":" or SP
* 1: @, look for a following { to reject @{ in refs (SIMD or = 0)
* 2: \0: End-of-component and string
* 3: /: End-of-component (SIMD or = 2)
* 4: ., look for a preceding . to reject .. in refs
* 5: {, look for a preceding @ to reject @{ in refs
* 6: *, usually a bad character except, once as a wildcard (SIMD or = 7)
* 7: A bad character except * (see check_refname_component below)
*/
static unsigned char refname_disposition[256] = {
1, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 2, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 4,
2, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 4, 3,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 7,
1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 7, 0, 7, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 4, 0, 4, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 4, 4
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 7, 7
};
/*
@ -33,8 +39,9 @@ static unsigned char refname_disposition[256] = {
* - any path component of it begins with ".", or
* - it has double dots "..", or
* - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
* - it ends with a "/".
* - it ends with ".lock"
* - it has pattern-matching notation "*", "?", "[", anywhere, or
* - it ends with a "/", or
* - it ends with ".lock", or
* - it contains a "\" (backslash)
*/
static int check_refname_component(const char *refname, int flags)
@ -46,17 +53,19 @@ static int check_refname_component(const char *refname, int flags)
int ch = *cp & 255;
unsigned char disp = refname_disposition[ch];
switch (disp) {
case 1:
case 2: /* fall-through */
case 3:
goto out;
case 2:
case 4:
if (last == '.')
return -1; /* Refname contains "..". */
break;
case 3:
case 5:
if (last == '@')
return -1; /* Refname contains "@{". */
break;
case 4:
case 6: /* fall-through */
case 7:
return -1;
}
last = ch;
@ -79,7 +88,7 @@ out:
return cp - refname;
}
int check_refname_format(const char *refname, int flags)
static int check_refname_format_bytewise(const char *refname, int flags)
{
int component_len, component_count = 0;
@ -115,6 +124,195 @@ int check_refname_format(const char *refname, int flags)
return 0;
}
#if defined(__GNUC__) && defined(__x86_64__)
#define SSE_VECTOR_BYTES 16
/* Vectorized version of check_refname_format. */
int check_refname_format(const char *refname, int flags)
{
const char *cp = refname;
const __m128i dot = _mm_set1_epi8('.');
const __m128i at = _mm_set1_epi8('@');
const __m128i curly = _mm_set1_epi8('{');
const __m128i slash = _mm_set1_epi8('/');
const __m128i zero = _mm_set1_epi8('\000');
const __m128i el = _mm_set1_epi8('l');
/* below '*', all characters are forbidden or rare */
const __m128i star_ub = _mm_set1_epi8('*' + 1);
const __m128i colon = _mm_set1_epi8(':');
const __m128i question = _mm_set1_epi8('?');
/* '['..'^' contains 4 characters: 3 forbidden and 1 rare */
const __m128i bracket_lb = _mm_set1_epi8('[' - 1);
const __m128i caret_ub = _mm_set1_epi8('^' + 1);
/* '~' and above are forbidden */
const __m128i tilde_lb = _mm_set1_epi8('~' - 1);
int component_count = 0;
if (refname[0] == 0 || refname[0] == '/') {
/* entirely empty ref or initial ref component */
return -1;
}
/*
* Initial ref component of '.'; below we look for /. so we'll
* miss this.
*/
if (refname[0] == '.') {
if (refname[1] == '/' || refname[1] == '\0')
return -1;
if (!(flags & REFNAME_DOT_COMPONENT))
return -1;
}
while(1) {
__m128i tmp, tmp1, result;
uint64_t mask;
if ((uintptr_t) cp % PAGE_SIZE > PAGE_SIZE - SSE_VECTOR_BYTES - 1)
/*
* End-of-page; fall back to slow method for
* this entire ref.
*/
return check_refname_format_bytewise(refname, flags);
tmp = _mm_loadu_si128((__m128i *)cp);
tmp1 = _mm_loadu_si128((__m128i *)(cp + 1));
/*
* This range (note the lt) contains some
* permissible-but-rare characters (including all
* characters >= 128), which we handle later. It also
* includes \000.
*/
result = _mm_cmplt_epi8(tmp, star_ub);
result = _mm_or_si128(result, _mm_cmpeq_epi8(tmp, question));
result = _mm_or_si128(result, _mm_cmpeq_epi8(tmp, colon));
/* This range contains the permissible ] as bycatch */
result = _mm_or_si128(result, _mm_and_si128(
_mm_cmpgt_epi8(tmp, bracket_lb),
_mm_cmplt_epi8(tmp, caret_ub)));
result = _mm_or_si128(result, _mm_cmpgt_epi8(tmp, tilde_lb));
/* .. */
result = _mm_or_si128(result, _mm_and_si128(
_mm_cmpeq_epi8(tmp, dot),
_mm_cmpeq_epi8(tmp1, dot)));
/* @{ */
result = _mm_or_si128(result, _mm_and_si128(
_mm_cmpeq_epi8(tmp, at),
_mm_cmpeq_epi8(tmp1, curly)));
/* // */
result = _mm_or_si128(result, _mm_and_si128(
_mm_cmpeq_epi8(tmp, slash),
_mm_cmpeq_epi8(tmp1, slash)));
/* trailing / */
result = _mm_or_si128(result, _mm_and_si128(
_mm_cmpeq_epi8(tmp, slash),
_mm_cmpeq_epi8(tmp1, zero)));
/* .l, beginning of .lock */
result = _mm_or_si128(result, _mm_and_si128(
_mm_cmpeq_epi8(tmp, dot),
_mm_cmpeq_epi8(tmp1, el)));
/*
* Even though /. is not necessarily an error, we flag
* it anyway. If we find it, we'll check if it's valid
* and if so we'll advance just past it.
*/
result = _mm_or_si128(result, _mm_and_si128(
_mm_cmpeq_epi8(tmp, slash),
_mm_cmpeq_epi8(tmp1, dot)));
mask = _mm_movemask_epi8(result);
if (mask) {
/*
* We've found either end-of-string, or some
* probably-bad character or substring.
*/
int i = __builtin_ctz(mask);
switch (refname_disposition[cp[i] & 255]) {
case 0: /* fall-through */
case 5:
/*
* bycatch: a good character that's in
* one of the ranges of mostly-forbidden
* characters
*/
cp += i + 1;
break;
case 1:
if (cp[i + 1] == '{')
return -1;
cp += i + 1;
break;
case 2:
if (!(flags & REFNAME_ALLOW_ONELEVEL)
&& !component_count && !strchr(refname, '/'))
/* Refname has only one component. */
return -1;
return 0;
case 3:
component_count ++;
/*
* Even if leading dots are allowed, don't
* allow "." as a component (".." is
* prevented by case 4 below).
*/
if (cp[i + 1] == '.') {
if (cp[i + 2] == '\0')
return -1;
if (flags & REFNAME_DOT_COMPONENT) {
/* skip to just after the /. */
cp += i + 2;
break;
}
return -1;
} else if (cp[i + 1] == '/' || cp[i + 1] == '\0')
return -1;
break;
case 4:
if (cp[i + 1] == '.' || cp[i + 1] == '\0')
return -1;
/* .lock as end-of-component or end-of-string */
if ((!strncmp(cp + i, ".lock", 5))
&& (cp[i + 5] == '/' || cp[i + 5] == 0))
return -1;
cp += 1;
break;
case 6:
if (((cp == refname + i) || cp[i - 1] == '/')
&& (cp[i + 1] == '/' || cp[i + 1] == 0))
if (flags & REFNAME_REFSPEC_PATTERN) {
flags &= ~REFNAME_REFSPEC_PATTERN;
/* restart after the * */
cp += i + 1;
continue;
}
/* fall-through */
case 7:
return -1;
}
} else
cp += SSE_VECTOR_BYTES;
}
}
#else
int check_refname_format (const char *refname, int flags)
{
return check_refname_format_bytewise(refname, flags);
}
#endif
struct ref_entry;
/*

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@ -64,6 +64,7 @@ valid_ref "$(printf 'heads/fu\303\237')"
invalid_ref 'heads/*foo/bar' --refspec-pattern
invalid_ref 'heads/foo*/bar' --refspec-pattern
invalid_ref 'heads/f*o/bar' --refspec-pattern
invalid_ref 'heads/foo*//bar' --refspec-pattern
ref='foo'
invalid_ref "$ref"
@ -128,6 +129,20 @@ valid_ref NOT_MINGW "$ref" '--allow-onelevel --normalize'
invalid_ref NOT_MINGW "$ref" '--refspec-pattern --normalize'
valid_ref NOT_MINGW "$ref" '--refspec-pattern --allow-onelevel --normalize'
valid_ref 'refs/heads/a-very-long-refname'
invalid_ref 'refs/heads/.a-very-long-refname'
invalid_ref 'refs/heads/abcdefgh0123..'
invalid_ref 'refs/heads/abcdefgh01234..'
invalid_ref 'refs/heads/abcdefgh012345..'
invalid_ref 'refs/heads/abcdefgh0123456..'
invalid_ref 'refs/heads/abcdefgh01234567..'
valid_ref 'refs/heads/abcdefgh0123.a'
valid_ref 'refs/heads/abcdefgh01234.a'
valid_ref 'refs/heads/abcdefgh012345.a'
valid_ref 'refs/heads/abcdefgh0123456.a'
valid_ref 'refs/heads/abcdefgh01234567.a'
test_expect_success "check-ref-format --branch @{-1}" '
T=$(git write-tree) &&
sha1=$(echo A | git commit-tree $T) &&

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@ -49,3 +49,11 @@
Memcheck:Addr4
fun:copy_ref
}
{
ignore-sse-check_refname_format
Memcheck:Addr8
fun:check_refname_format
fun:cmd_check_ref_format
fun:handle_builtin
fun:main
}