Performance Optimization: Reduce strlen calls in literal matching. 500% faster.

[soasme]

A bottleneck on the performance is spotted. Given the following callgrind report, strlen is called frequently.

root@e9e1f33a922d:/app/buildlinux# callgrind_annotate callgrind.out.4864
--------------------------------------------------------------------------------
Profile data file 'callgrind.out.4864' (creator: callgrind-3.15.0)
--------------------------------------------------------------------------------
I1 cache:
D1 cache:
LL cache:
Timerange: Basic block 0 - 2999929205
Trigger: Program termination
Profiled target:  ./cli ast --grammar-file ../tests/golang-v1.17.peg --grammar-entry SourceFile ../tables.go (PID 4864, part 1)
Events recorded:  Ir
Events shown:     Ir
Event sort order: Ir
Thresholds:       99
Include dirs:
User annotated:
Auto-annotation:  off

--------------------------------------------------------------------------------
Ir
--------------------------------------------------------------------------------
17,147,795,601  PROGRAM TOTALS

--------------------------------------------------------------------------------
Ir             file:function
--------------------------------------------------------------------------------
5,671,628,114  /build/glibc-eX1tMB/glibc-2.31/string/../sysdeps/x86_64/multiarch/strlen-avx2.S:__strlen_avx2 [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
2,285,786,104  /build/glibc-eX1tMB/glibc-2.31/stdio-common/vfprintf-internal.c:__vfprintf_internal [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
2,082,168,585  /build/glibc-eX1tMB/glibc-2.31/libio/genops.c:_IO_default_xsputn [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
  751,814,539  /build/glibc-eX1tMB/glibc-2.31/malloc/malloc.c:_int_free [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
  745,634,925  /app/peppa.c:push_frame [/app/buildlinux/libpeppa.so]
  727,083,049  /app/peppa.c:match_expression'2 [/app/buildlinux/libpeppa.so]
  491,138,084  /build/glibc-eX1tMB/glibc-2.31/malloc/malloc.c:malloc [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
  448,750,552  /app/peppa.c:match_sequence'2 [/app/buildlinux/libpeppa.so]
  356,035,185  /build/glibc-eX1tMB/glibc-2.31/string/../sysdeps/x86_64/multiarch/strchr-avx2.S:__strchrnul_avx2 [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
  337,972,930  /build/glibc-eX1tMB/glibc-2.31/stdio-common/_itoa.c:_itoa_word [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
  281,391,553  /app/peppa.c:pop_frame [/app/buildlinux/libpeppa.so]
  270,636,280  /app/peppa.c:match_literal [/app/buildlinux/libpeppa.so]
  249,880,289  /build/glibc-eX1tMB/glibc-2.31/malloc/malloc.c:free [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
  197,488,154  /app/peppa.c:match_choice'2 [/app/buildlinux/libpeppa.so]
  195,408,976  /build/glibc-eX1tMB/glibc-2.31/libio/iovsprintf.c:__vsprintf_internal [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
  170,253,828  /app/peppa.c:match_repeat'2 [/app/buildlinux/libpeppa.so]
  145,621,806  /app/peppa.c:P4_GetWhitespaces [/app/buildlinux/libpeppa.so]
  145,144,850  /build/glibc-eX1tMB/glibc-2.31/stdio-common/../libio/libioP.h:__vfprintf_internal
  143,067,286  /build/glibc-eX1tMB/glibc-2.31/libio/strops.c:_IO_str_init_static_internal [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
  135,547,068  /app/peppa.c:match_reference'2 [/app/buildlinux/libpeppa.so]
  119,417,954  /app/peppa.c:match_range [/app/buildlinux/libpeppa.so]
  113,404,878  /app/peppa.c:P4_DeleteNode [/app/buildlinux/libpeppa.so]
   97,704,488  /build/glibc-eX1tMB/glibc-2.31/stdio-common/sprintf.c:sprintf [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
   92,107,686  /app/peppa.c:u8_next_char [/app/buildlinux/libpeppa.so]
   92,018,744  /build/glibc-eX1tMB/glibc-2.31/stdio-common/printf-parse.h:__vfprintf_internal
   87,236,285  /build/glibc-eX1tMB/glibc-2.31/libio/genops.c:_IO_setb [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
   84,817,686  /build/glibc-eX1tMB/glibc-2.31/libio/libioP.h:_IO_default_xsputn
   80,257,318  /build/glibc-eX1tMB/glibc-2.31/libio/genops.c:_IO_no_init [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
   73,278,412  /build/glibc-eX1tMB/glibc-2.31/libio/genops.c:_IO_old_init [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
   62,810,208  /build/glibc-eX1tMB/glibc-2.31/string/../sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S:__memset_avx2_unaligned_erms [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
   62,469,889  /build/glibc-eX1tMB/glibc-2.31/malloc/malloc.c:_int_malloc [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
   33,790,679  /app/peppa.c:P4_DiffPosition [/app/buildlinux/libpeppa.so]
   33,770,484  /app/peppa.c:cleanup_freep [/app/buildlinux/libpeppa.so]
   33,029,980  ???:0x000000000487c390 [???]
   29,849,862  /app/peppa.c:P4_CaseCmpInsensitive [/app/buildlinux/libpeppa.so]
   29,210,137  /build/glibc-eX1tMB/glibc-2.31/string/../sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S:__memcmp_avx2_movbe [/usr/lib/x86_64-linux-gnu/libc-2.31.so]
   24,344,373  ???:0x000000000483a5f0 [???]

Compare the time stats:

Before:

real	0m47.054s
user	0m44.259s
sys	0m0.234s

After

real	0m12.089s
user	0m9.655s
sys	0m0.107s

Attachment:

• tables.go.