path: root/t
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authorÆvar Arnfjörð Bjarmason <>2017-06-01 18:20:56 (GMT)
committerJunio C Hamano <>2017-06-01 23:29:05 (GMT)
commit94da9193a6eb8f1085d611c04ff8bbb4f5ae1e0a (patch)
tree9a6ea07f5e0e77e7330eb83e8ed486af27932427 /t
parentfb95e2e38dd4e8301b3992bacfac4c87b8262181 (diff)
grep: add support for PCRE v2
Add support for v2 of the PCRE API. This is a new major version of PCRE that came out in early 2015[1]. The regular expression syntax is the same, but while the API is similar, pretty much every function is either renamed or takes different arguments. Thus using it via entirely new functions makes sense, as opposed to trying to e.g. have one compile_pcre_pattern() that would call either PCRE v1 or v2 functions. Git can now be compiled with either USE_LIBPCRE1=YesPlease or USE_LIBPCRE2=YesPlease, with USE_LIBPCRE=YesPlease currently being a synonym for the former. Providing both is a compile-time error. With earlier patches to enable JIT for PCRE v1 the performance of the release versions of both libraries is almost exactly the same, with PCRE v2 being around 1% slower. However after I reported this to the pcre-dev mailing list[2] I got a lot of help with the API use from Zoltán Herczeg, he subsequently optimized some of the JIT functionality in v2 of the library. Running the performance test against the latest Subversion trunk of both, with both them and git compiled as -O3, and the test run against linux.git, gives the following results. Just the /perl/ tests shown: $ GIT_PERF_REPEAT_COUNT=30 GIT_PERF_LARGE_REPO=~/g/linux GIT_PERF_MAKE_COMMAND='grep -q LIBPCRE2 Makefile && make -j8 USE_LIBPCRE2=YesPlease CC=~/perl5/installed/bin/gcc NO_R_TO_GCC_LINKER=YesPlease CFLAGS=-O3 LIBPCREDIR=/home/avar/g/pcre2/inst LDFLAGS=-Wl,-rpath,/home/avar/g/pcre2/inst/lib || make -j8 USE_LIBPCRE=YesPlease CC=~/perl5/installed/bin/gcc NO_R_TO_GCC_LINKER=YesPlease CFLAGS=-O3 LIBPCREDIR=/home/avar/g/pcre/inst LDFLAGS=-Wl,-rpath,/home/avar/g/pcre/inst/lib' ./run HEAD~5 HEAD~ HEAD [...] Test HEAD~5 HEAD~ HEAD ----------------------------------------------------------------------------------------------------------------- 7820.3: perl grep '' 0.31(1.10+0.48) 0.21(0.35+0.56) -32.3% 0.21(0.34+0.55) -32.3% 7820.7: perl grep '^how to' 0.56(2.70+0.40) 0.24(0.64+0.52) -57.1% 0.20(0.28+0.60) -64.3% 7820.11: perl grep '[how] to' 0.56(2.66+0.38) 0.29(0.95+0.45) -48.2% 0.23(0.45+0.54) -58.9% 7820.15: perl grep '(e.t[^ ]*|v.ry) rare' 1.02(5.77+0.42) 0.31(1.02+0.54) -69.6% 0.23(0.50+0.54) -77.5% 7820.19: perl grep 'm(ú|u)lt.b(æ|y)te' 0.38(1.57+0.42) 0.27(0.85+0.46) -28.9% 0.21(0.33+0.57) -44.7% See commit ("perf: add a comparison test of grep regex engines", 2017-04-19) for details on the machine the above test run was executed on. Here HEAD~2 is git with PCRE v1 without JIT, HEAD~ is PCRE v1 with JIT, and HEAD is PCRE v2 (also with JIT). See previous commits of mine mentioning for more details on the test setup. For ease of readability, a different run just of HEAD~ (PCRE v1 with JIT v.s. PCRE v2), again with just the /perl/ tests shown: [...] Test HEAD~ HEAD ---------------------------------------------------------------------------------------- 7820.3: perl grep '' 0.21(0.42+0.52) 0.21(0.31+0.58) +0.0% 7820.7: perl grep '^how to' 0.25(0.65+0.50) 0.20(0.31+0.57) -20.0% 7820.11: perl grep '[how] to' 0.30(0.90+0.50) 0.23(0.46+0.53) -23.3% 7820.15: perl grep '(e.t[^ ]*|v.ry) rare' 0.30(1.19+0.38) 0.23(0.51+0.51) -23.3% 7820.19: perl grep 'm(ú|u)lt.b(æ|y)te' 0.27(0.84+0.48) 0.21(0.34+0.57) -22.2% I.e. the two are either neck-to-neck, but PCRE v2 usually pulls ahead, when it does it's around 20% faster. A brief note on thread safety: As noted in pcre2api(3) & pcre2jit(3) the compiled pattern can be shared between threads, but not some of the JIT context, however the grep threading support does all pattern & JIT compilation in separate threads, so this code doesn't need to concern itself with thread safety. See commit 63e7e9d8b6 ("git-grep: Learn PCRE", 2011-05-09) for the initial addition of PCRE v1. This change follows some of the same patterns it did (and which were discussed on list at the time), e.g. mocking up types with typedef instead of ifdef-ing them out when USE_LIBPCRE2 isn't defined. This adds some trivial memory use to the program, but makes the code look nicer. 1. 2. Signed-off-by: Ævar Arnfjörð Bjarmason <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 't')
1 files changed, 1 insertions, 1 deletions
diff --git a/t/ b/t/
index ab92c0e..44d4679 100644
--- a/t/
+++ b/t/
@@ -1011,7 +1011,7 @@ esac
test -z "$NO_PERL" && test_set_prereq PERL
test -z "$NO_PTHREADS" && test_set_prereq PTHREADS
test -z "$NO_PYTHON" && test_set_prereq PYTHON
-test -n "$USE_LIBPCRE1" && test_set_prereq PCRE
+test -n "$USE_LIBPCRE1$USE_LIBPCRE2" && test_set_prereq PCRE
test -z "$NO_GETTEXT" && test_set_prereq GETTEXT
# Can we rely on git's output in the C locale?