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Unroll performance-critical loops 4x

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Use a special macro that unrolls the loop body and uses static branch prediction
to improve code generation.

This increases performance across all data sets from benchmark; clang x64 is 10%-40%
faster, clang x86 is 5%-20% faster, msvc is 5%-10% faster.

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1008 99668b35-9821-0410-8761-19e4c4f06640
This commit is contained in:
Arseny Kapoulkine 2014-08-26 06:10:52 +00:00
parent 0f5101bfc5
commit 211212c986
1 changed files with 19 additions and 9 deletions
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28
src/pugixml.cpp
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@ -84,6 +84,13 @@
# define PUGI__NO_INLINE # define PUGI__NO_INLINE
#endif #endif
// Branch weight controls
#if defined(__GNUC__)
# define PUGI__UNLIKELY(cond) __builtin_expect(cond, 0)
#else
# define PUGI__UNLIKELY(cond) (cond)
#endif
// Simple static assertion // Simple static assertion
#define PUGI__STATIC_ASSERT(cond) { static const char condition_failed[(cond) ? 1 : -1] = {0}; (void)condition_failed[0]; } #define PUGI__STATIC_ASSERT(cond) { static const char condition_failed[(cond) ? 1 : -1] = {0}; (void)condition_failed[0]; }
@ -1896,6 +1903,7 @@ PUGI__NS_BEGIN
#define PUGI__POPNODE() { cursor = cursor->parent; } #define PUGI__POPNODE() { cursor = cursor->parent; }
#define PUGI__SCANFOR(X) { while (*s != 0 && !(X)) ++s; } #define PUGI__SCANFOR(X) { while (*s != 0 && !(X)) ++s; }
#define PUGI__SCANWHILE(X) { while (X) ++s; } #define PUGI__SCANWHILE(X) { while (X) ++s; }
#define PUGI__SCANWHILE_UNROLL(X) { while (X) { ++s; if (PUGI__UNLIKELY(!(X))) break; ++s; if (PUGI__UNLIKELY(!(X))) break; ++s; if (PUGI__UNLIKELY(!(X))) break; ++s; } }
#define PUGI__ENDSEG() { ch = *s; *s = 0; ++s; } #define PUGI__ENDSEG() { ch = *s; *s = 0; ++s; }
#define PUGI__THROW_ERROR(err, m) return error_offset = m, error_status = err, static_cast<char_t*>(0) #define PUGI__THROW_ERROR(err, m) return error_offset = m, error_status = err, static_cast<char_t*>(0)
#define PUGI__CHECK_ERROR(err, m) { if (*s == 0) PUGI__THROW_ERROR(err, m); } #define PUGI__CHECK_ERROR(err, m) { if (*s == 0) PUGI__THROW_ERROR(err, m); }
@ -1906,7 +1914,7 @@ PUGI__NS_BEGIN
while (true) while (true)
{ {
PUGI__SCANWHILE(!PUGI__IS_CHARTYPE(*s, ct_parse_comment)); PUGI__SCANWHILE_UNROLL(!PUGI__IS_CHARTYPE(*s, ct_parse_comment));
if (*s == '\r') // Either a single 0x0d or 0x0d 0x0a pair if (*s == '\r') // Either a single 0x0d or 0x0d 0x0a pair
{ {
@ -1934,7 +1942,7 @@ PUGI__NS_BEGIN
while (true) while (true)
{ {
PUGI__SCANWHILE(!PUGI__IS_CHARTYPE(*s, ct_parse_cdata)); PUGI__SCANWHILE_UNROLL(!PUGI__IS_CHARTYPE(*s, ct_parse_cdata));
if (*s == '\r') // Either a single 0x0d or 0x0d 0x0a pair if (*s == '\r') // Either a single 0x0d or 0x0d 0x0a pair
{ {
@ -1968,7 +1976,7 @@ PUGI__NS_BEGIN
while (true) while (true)
{ {
PUGI__SCANWHILE(!PUGI__IS_CHARTYPE(*s, ct_parse_pcdata)); PUGI__SCANWHILE_UNROLL(!PUGI__IS_CHARTYPE(*s, ct_parse_pcdata));
if (*s == '<') // PCDATA ends here if (*s == '<') // PCDATA ends here
{ {
@ -2048,7 +2056,7 @@ PUGI__NS_BEGIN
while (true) while (true)
{ {
PUGI__SCANWHILE(!PUGI__IS_CHARTYPE(*s, ct_parse_attr_ws | ct_space)); PUGI__SCANWHILE_UNROLL(!PUGI__IS_CHARTYPE(*s, ct_parse_attr_ws | ct_space));
if (*s == end_quote) if (*s == end_quote)
{ {
@ -2089,7 +2097,7 @@ PUGI__NS_BEGIN
while (true) while (true)
{ {
PUGI__SCANWHILE(!PUGI__IS_CHARTYPE(*s, ct_parse_attr_ws)); PUGI__SCANWHILE_UNROLL(!PUGI__IS_CHARTYPE(*s, ct_parse_attr_ws));
if (*s == end_quote) if (*s == end_quote)
{ {
@ -2125,7 +2133,7 @@ PUGI__NS_BEGIN
while (true) while (true)
{ {
PUGI__SCANWHILE(!PUGI__IS_CHARTYPE(*s, ct_parse_attr)); PUGI__SCANWHILE_UNROLL(!PUGI__IS_CHARTYPE(*s, ct_parse_attr));
if (*s == end_quote) if (*s == end_quote)
{ {
@ -2157,7 +2165,7 @@ PUGI__NS_BEGIN
while (true) while (true)
{ {
PUGI__SCANWHILE(!PUGI__IS_CHARTYPE(*s, ct_parse_attr)); PUGI__SCANWHILE_UNROLL(!PUGI__IS_CHARTYPE(*s, ct_parse_attr));
if (*s == end_quote) if (*s == end_quote)
{ {
@ -2559,7 +2567,7 @@ PUGI__NS_BEGIN
cursor->name = s; cursor->name = s;
PUGI__SCANWHILE(PUGI__IS_CHARTYPE(*s, ct_symbol)); // Scan for a terminator. PUGI__SCANWHILE_UNROLL(PUGI__IS_CHARTYPE(*s, ct_symbol)); // Scan for a terminator.
PUGI__ENDSEG(); // Save char in 'ch', terminate & step over. PUGI__ENDSEG(); // Save char in 'ch', terminate & step over.
if (ch == '>') if (ch == '>')
@ -2580,7 +2588,7 @@ PUGI__NS_BEGIN
a->name = s; // Save the offset. a->name = s; // Save the offset.
PUGI__SCANWHILE(PUGI__IS_CHARTYPE(*s, ct_symbol)); // Scan for a terminator. PUGI__SCANWHILE_UNROLL(PUGI__IS_CHARTYPE(*s, ct_symbol)); // Scan for a terminator.
PUGI__CHECK_ERROR(status_bad_attribute, s); //$ redundant, left for performance PUGI__CHECK_ERROR(status_bad_attribute, s); //$ redundant, left for performance
PUGI__ENDSEG(); // Save char in 'ch', terminate & step over. PUGI__ENDSEG(); // Save char in 'ch', terminate & step over.
@ -10706,6 +10714,7 @@ namespace pugi
// Undefine all local macros (makes sure we're not leaking macros in header-only mode) // Undefine all local macros (makes sure we're not leaking macros in header-only mode)
#undef PUGI__NO_INLINE #undef PUGI__NO_INLINE
#undef PUGI__UNLIKELY
#undef PUGI__STATIC_ASSERT #undef PUGI__STATIC_ASSERT
#undef PUGI__DMC_VOLATILE #undef PUGI__DMC_VOLATILE
#undef PUGI__MSVC_CRT_VERSION #undef PUGI__MSVC_CRT_VERSION
@ -10723,6 +10732,7 @@ namespace pugi
#undef PUGI__POPNODE #undef PUGI__POPNODE
#undef PUGI__SCANFOR #undef PUGI__SCANFOR
#undef PUGI__SCANWHILE #undef PUGI__SCANWHILE
#undef PUGI__SCANWHILE_UNROLL
#undef PUGI__ENDSEG #undef PUGI__ENDSEG
#undef PUGI__THROW_ERROR #undef PUGI__THROW_ERROR
#undef PUGI__CHECK_ERROR #undef PUGI__CHECK_ERROR