peep.c: Add some UNLIKELY()

It's also unlikely that the op_type will be any given value, but I
expect the compiler and libc know that.

This stresses that it is unlikely some module will customize the
handling of these checkers.

Author: khwilliamson

peep.c

@@ -2206,17 +2206,17 @@ S_maybe_multideref(pTHX_ OP *start, OP *orig_o, UV orig_action, U8 hints)
              * abandon optimisation attempt.  Check two different ways because
              * of z/OS (see comments in opcode.h) */
             if (  (o->op_type == OP_AELEM || o->op_type == OP_HELEM)
-               && PL_check[o->op_type] != Perl_ck_null
-               && PL_check[o->op_type] != PL_check[PERL_CK_NULL])
+               && UNLIKELY(PL_check[o->op_type] != Perl_ck_null)
+               && UNLIKELY(PL_check[o->op_type] != PL_check[PERL_CK_NULL]))
                 return;
             /* similarly for customised exists and delete */
             if (  (o->op_type == OP_EXISTS)
-               && PL_check[OP_EXISTS] != Perl_ck_exists
-               && PL_check[OP_EXISTS] != PL_check[PERL_CK_EXISTS])
+               && UNLIKELY(PL_check[OP_EXISTS] != Perl_ck_exists)
+               && UNLIKELY(PL_check[OP_EXISTS] != PL_check[PERL_CK_EXISTS]))
                 return;
             if (  (o->op_type == OP_DELETE)
-               && PL_check[OP_DELETE] != Perl_ck_delete
-               && PL_check[OP_DELETE] != PL_check[PERL_CK_DELETE])
+               && UNLIKELY(PL_check[OP_DELETE] != Perl_ck_delete)
+               && UNLIKELY(PL_check[OP_DELETE] != PL_check[PERL_CK_DELETE]))
                 return;
 
             if (   o->op_type != OP_AELEM