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[sanitizer] optimize internal_memset for the most performance critical case (16-byte-aligned) 

llvm-svn: 341420
This commit is contained in:
Kostya Serebryany 2018-09-04 22:43:30 +00:00
parent ec277a8278
commit 470db78115
1 changed files with 12 additions and 0 deletions
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12
compiler-rt/lib/sanitizer_common/sanitizer_libc.cc
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@ -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