From 211212c9861834c2f8327a1efe6690a893365823 Mon Sep 17 00:00:00 2001 From: Arseny Kapoulkine Date: Tue, 26 Aug 2014 06:10:52 +0000 Subject: Unroll performance-critical loops 4x 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 --- src/pugixml.cpp | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-) (limited to 'src') diff --git a/src/pugixml.cpp b/src/pugixml.cpp index 026921f..ad2262f 100644 --- a/src/pugixml.cpp +++ b/src/pugixml.cpp @@ -84,6 +84,13 @@ # define PUGI__NO_INLINE #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 #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__SCANFOR(X) { while (*s != 0 && !(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__THROW_ERROR(err, m) return error_offset = m, error_status = err, static_cast(0) #define PUGI__CHECK_ERROR(err, m) { if (*s == 0) PUGI__THROW_ERROR(err, m); } @@ -1906,7 +1914,7 @@ PUGI__NS_BEGIN 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 { @@ -1934,7 +1942,7 @@ PUGI__NS_BEGIN 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 { @@ -1968,7 +1976,7 @@ PUGI__NS_BEGIN 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 { @@ -2048,7 +2056,7 @@ PUGI__NS_BEGIN 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) { @@ -2089,7 +2097,7 @@ PUGI__NS_BEGIN 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) { @@ -2125,7 +2133,7 @@ PUGI__NS_BEGIN 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) { @@ -2157,7 +2165,7 @@ PUGI__NS_BEGIN 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) { @@ -2559,7 +2567,7 @@ PUGI__NS_BEGIN 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. if (ch == '>') @@ -2580,7 +2588,7 @@ PUGI__NS_BEGIN 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__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) #undef PUGI__NO_INLINE +#undef PUGI__UNLIKELY #undef PUGI__STATIC_ASSERT #undef PUGI__DMC_VOLATILE #undef PUGI__MSVC_CRT_VERSION @@ -10723,6 +10732,7 @@ namespace pugi #undef PUGI__POPNODE #undef PUGI__SCANFOR #undef PUGI__SCANWHILE +#undef PUGI__SCANWHILE_UNROLL #undef PUGI__ENDSEG #undef PUGI__THROW_ERROR #undef PUGI__CHECK_ERROR -- cgit v1.2.3