[Bug sanitizer/55309] gcc's address-sanitizer 66% slower than clang's

[kcc at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55309



--- Comment #53 from Kostya Serebryany <kcc at gcc dot gnu.org> 2013-02-22 
15:06:25 UTC ---

The interceptor we have is conservative: 



INTERCEPTOR(int, memcmp, const void *a1, const void *a2, uptr size) {

  if (!asan_inited) return internal_memcmp(a1, a2, size);

  ENSURE_ASAN_INITED();

  unsigned char c1 = 0, c2 = 0;

  const unsigned char *s1 = (const unsigned char*)a1;

  const unsigned char *s2 = (const unsigned char*)a2;

  uptr i;

  for (i = 0; i < size; i++) {

    c1 = s1[i];

    c2 = s2[i];

    if (c1 != c2) break;

  }

  ASAN_READ_RANGE(s1, Min(i + 1, size));

  ASAN_READ_RANGE(s2, Min(i + 1, size));

  return CharCmp(c1, c2);

} 



looks like gcc partially inlines memcmp and 

bypasses out conservative interceptor.



We could make the interceptor more strict (ASAN_READ_RANGE(s2, size);).

I am trying to remember why we didn't do this...