libsanitizer mege from upstream r171973

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@195083 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 19 insertions, 0 deletions

diff --git a/libsanitizer/sanitizer_common/sanitizer_libc.cc b/libsanitizer/sanitizer_common/sanitizer_libc.cc
index 4d43cd7d013..b02cbd4aced 100644
--- a/libsanitizer/sanitizer_common/sanitizer_libc.cc
+++ b/libsanitizer/sanitizer_common/sanitizer_libc.cc
@@ -203,4 +203,23 @@ s64 internal_simple_strtoll(const char *nptr, char **endptr, int base) {
   }
 }
 
+bool mem_is_zero(const char *beg, uptr size) {
+  CHECK_LE(size, 1UL << FIRST_32_SECOND_64(30, 40));  // Sanity check.
+  const char *end = beg + size;
+  uptr *aligned_beg = (uptr *)RoundUpTo((uptr)beg, sizeof(uptr));
+  uptr *aligned_end = (uptr *)RoundDownTo((uptr)end, sizeof(uptr));
+  uptr all = 0;
+  // Prologue.
+  for (const char *mem = beg; mem < (char*)aligned_beg && mem < end; mem++)
+    all |= *mem;
+  // Aligned loop.
+  for (; aligned_beg < aligned_end; aligned_beg++)
+    all |= *aligned_beg;
+  // Epilogue.
+  if ((char*)aligned_end >= beg)
+    for (const char *mem = (char*)aligned_end; mem < end; mem++)
+      all |= *mem;
+  return all == 0;
+}
+
 }  // namespace __sanitizer