regcomp: reduce some code duplication

The tail of each branch is basically the same, so we can pull out the
common code. Also, we don't need to SvIV() twice if we store the result
of the first call in a local variable.

Addresses Perl#23364.

Author: mauke

regcomp.c

@@ -395,26 +395,28 @@ Perl_reginitcolors(pTHX)
 regexp_engine const *
 Perl_current_re_engine(pTHX)
 {
+    SV *ptr;
     if (IN_PERL_COMPILETIME) {
         HV * const table = GvHV(PL_hintgv);
-        SV **ptr;
+        SV **pptr;
 
         if (!table || !(PL_hints & HINT_LOCALIZE_HH))
             return &PL_core_reg_engine;
-        ptr = hv_fetchs(table, "regcomp", false);
-        if ( !(ptr && SvIOK(*ptr) && SvIV(*ptr)))
+        pptr = hv_fetchs(table, "regcomp", false);
+        if (!pptr)
             return &PL_core_reg_engine;
-        return INT2PTR(regexp_engine*, SvIV(*ptr));
+        ptr = *pptr;
     }
     else {
-        SV *ptr;
         if (!PL_curcop->cop_hints_hash)
             return &PL_core_reg_engine;
         ptr = cop_hints_fetch_pvs(PL_curcop, "regcomp", 0);
-        if ( !(ptr && SvIOK(ptr) && SvIV(ptr)))
-            return &PL_core_reg_engine;
-        return INT2PTR(regexp_engine*, SvIV(ptr));
     }
+
+    IV iv;
+    if ( !(ptr && SvIOK(ptr) && (iv = SvIV(ptr))) )
+        return &PL_core_reg_engine;
+    return INT2PTR(regexp_engine*, iv);
 }