[Bug tree-optimization/102382] New: Missing optimization for strlen after enable O2 vectorization

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102382

            Bug ID: 102382
           Summary: Missing optimization for strlen after enable O2
                    vectorization
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: crazylht at gmail dot com
  Target Milestone: ---

testcase is from strlenopt-85.c

void* elim_strlen_calloc_store_memset_1 (unsigned a, unsigned b)
{
  char *p = __builtin_calloc (a, 1);

  p[0] = '\0';
  p[1] = '\0';
  p[2] = '\0';
  p[3] = '\0';

  __builtin_memset (p, 0, b);

  n0 = __builtin_strlen (p);

  return p;
}

diff --git a/strlenopt-85.c.193t.strlen1
b/../vectorize/strlenopt-85.c.193t.strlen1
index 2c8bc4a..6591d9e 100644
--- a/strlenopt-85.c.193t.strlen1
+++ b/../vectorize/strlenopt-85.c.193t.strlen1
@@ -10,6 +10,8 @@
 ;; 2 succs { 1 }
 void * elim_strlen_calloc_store_memset_1 (unsigned int a, unsigned int b)
 {
+  vector(4) char * vectp.5;
+  vector(4) char * vectp_p.4;
   char * p;
   long unsigned int _1;
   long unsigned int _2;
@@ -19,11 +21,10 @@ void * elim_strlen_calloc_store_memset_1 (unsigned int a,
unsigned int b)
   <bb 2> [local count: 1073741824]:
   _1 = (long unsigned int) a_5(D);
   p_8 = __builtin_calloc (_1, 1);
-  MEM[(char *)p_8 + 1B] = 0;
-  MEM[(char *)p_8 + 2B] = 0;
-  MEM[(char *)p_8 + 3B] = 0;
+  MEM <vector(4) char> [(char *)p_8] = { 0, 0, 0, 0 };
   _2 = (long unsigned int) b_13(D);
-  _3 = 0;
+  __builtin_memset (p_8, 0, _2);
+  _3 = __builtin_strlen (p_8);
   _4 = (unsigned int) _3;
   n0 = _4;
   return p_8;

It seems to be a missing optimization here.