commit cccbf4671c9372c396b1fab168d8c68af0e444fa
author Paul Wankadia <junyer@google.com> Tue Jul 06 21:38:25 2021 -0700
committer Paul Wankadia <junyer@google.com> Wed Jul 07 04:39:41 2021 +0000
tree a9ae759e76e012dcc283f4e8cebf35aff7b62914
parent baadb363939b3448f17136c1133180430dd53215

Flip the hot loops to do-while.

Change-Id: I4b33af6aa4c433a3c6b49bd39511ddfdfbb828a6
Reviewed-on: https://code-review.googlesource.com/c/re2/+/58932
Reviewed-by: Paul Wankadia <junyer@google.com>

re2/prog.cc

diff --git a/re2/prog.cc b/re2/prog.cc
index 3979bd2..a4b70bd 100644
--- a/re2/prog.cc
+++ b/re2/prog.cc
@@ -1035,7 +1035,7 @@
   if (size >= 8) {
     const uint8_t* p = reinterpret_cast<const uint8_t*>(data);
     const uint8_t* endp = p + (size&~7);
-    while (p != endp) {
+    do {
       uint8_t b0 = p[0];
       uint8_t b1 = p[1];
       uint8_t b2 = p[2];
@@ -1080,7 +1080,7 @@
 
       curr = curr7;
       p += 8;
-    }
+    } while (p != endp);
     data = p;
     size = size&7;
   }
@@ -1139,7 +1139,7 @@
     const __m256i* endfp = fp + size/sizeof(__m256i);
     const __m256i f_set1 = _mm256_set1_epi8(prefix_front_);
     const __m256i b_set1 = _mm256_set1_epi8(prefix_back_);
-    while (fp != endfp) {
+    do {
       const __m256i f_loadu = _mm256_loadu_si256(fp++);
       const __m256i b_loadu = _mm256_loadu_si256(bp++);
       const __m256i f_cmpeq = _mm256_cmpeq_epi8(f_set1, f_loadu);
@@ -1151,7 +1151,7 @@
         const int fb_ctz = FindLSBSet(fb_movemask);
         return reinterpret_cast<const char*>(fp-1) + fb_ctz;
       }
-    }
+    } while (fp != endfp);
     data = fp;
     size = size%sizeof(__m256i);
   }