[sanitizer] optimize internal_memset for the most performance critical case (16-byte-aligned)
@@ -73,6 +73,18 @@ void *internal_memmove(void *dest, const void *src, uptr n) {
}
void *internal_memset(void* s, int c, uptr n) {
+ // Optimize for the most performance-critical case:
+ if ((reinterpret_cast<uptr>(s) % 16) == 0 && (n % 16) == 0) {
+ u64 *p = reinterpret_cast<u64*>(s);
+ u64 *e = p + n / 8;
+ u64 v = c;
+ v |= v << 8;
+ v |= v << 16;
+ v |= v << 32;
+ for (; p < e; p += 2)
+ p[0] = p[1] = v;
+ return s;
+ }
// The next line prevents Clang from making a call to memset() instead of the
// loop below.
// FIXME: building the runtime with -ffreestanding is a better idea. However
