doop.c: Remove dead code

As the comments say, as of 5.32 we disallowed doing bitwise vector
operations on strings that contain code points that can't be converted
to bytes (i.e. above 0xFF).  Yet the code to do just that was left in,
but was intercepted by a croak before it got that far.

This removes that, and its calculations.

Author: khwilliamson

doop.c

@@ -1008,12 +1008,6 @@ Perl_do_vop(pTHX_ I32 optype, SV *sv, SV *left, SV *right)
     bool result_needs_to_be_utf8 = FALSE;
     bool left_utf8 = FALSE;
     bool right_utf8 = FALSE;
-    U8 * left_non_downgraded = NULL;
-    U8 * right_non_downgraded = NULL;
-    Size_t left_non_downgraded_len = 0;
-    Size_t right_non_downgraded_len = 0;
-    char * non_downgraded = NULL;
-    Size_t non_downgraded_len = 0;
 
     PERL_ARGS_ASSERT_DO_VOP;
 
@@ -1031,34 +1025,25 @@ Perl_do_vop(pTHX_ I32 optype, SV *sv, SV *left, SV *right)
     /* This needs to come after SvPV to ensure that string overloading has
        fired off.  */
 
-    /* Create downgraded temporaries of any UTF-8 encoded operands */
+    /* Create downgraded temporaries of any UTF-8 encoded operands.  As of
+     * perl-5.32, we no longer accept above-FF code points at all */
     if (DO_UTF8(left)) {
-        const U8 * save_lc = (U8 *) lc;
-
         left_utf8 = TRUE;
         result_needs_to_be_utf8 = TRUE;
 
-        left_non_downgraded_len = leftlen;
-        lc = (char *) bytes_from_utf8_loc((const U8 *) lc, &leftlen,
-                                          &left_utf8,
-                                          (const U8 **) &left_non_downgraded);
-        /* Calculate the number of trailing unconvertible bytes.  This quantity
-         * is the original length minus the length of the converted portion. */
-        left_non_downgraded_len -= left_non_downgraded - save_lc;
-        SAVEFREEPV(lc);
+        lc = (char *) bytes_from_utf8((const U8 *) lc, &leftlen, &left_utf8);
+        if (! left_utf8) {
+            SAVEFREEPV(lc);
+        }
     }
     if (DO_UTF8(right)) {
-        const U8 * save_rc = (U8 *) rc;
-
         right_utf8 = TRUE;
         result_needs_to_be_utf8 = TRUE;
 
-        right_non_downgraded_len = rightlen;
-        rc = (char *) bytes_from_utf8_loc((const U8 *) rc, &rightlen,
-                                          &right_utf8,
-                                          (const U8 **) &right_non_downgraded);
-        right_non_downgraded_len -= right_non_downgraded - save_rc;
-        SAVEFREEPV(rc);
+        rc = (char *) bytes_from_utf8((const U8 *) rc, &rightlen, &right_utf8);
+        if (! right_utf8) {
+            SAVEFREEPV(rc);
+        }
     }
 
     /* We set 'len' to the length that the operation actually operates on.  The
@@ -1069,9 +1054,7 @@ Perl_do_vop(pTHX_ I32 optype, SV *sv, SV *left, SV *right)
      * on zeros without having to do it.  In the case of '&', the result is
      * zero, and the dangling portion is simply discarded.  For '|' and '^', the
      * result is the same as the other operand, so the dangling part is just
-     * appended to the final result, unchanged.  As of perl-5.32, we no longer
-     * accept above-FF code points in the dangling portion.
-     */
+     * appended to the final result, unchanged. */
     if (left_utf8 || right_utf8) {
         Perl_croak(aTHX_ FATAL_ABOVE_FF_MSG, PL_op_desc[optype]);
     }
@@ -1173,29 +1156,11 @@ Perl_do_vop(pTHX_ I32 optype, SV *sv, SV *left, SV *right)
                 sv_catpvn_nomg(sv, lsave + len, leftlen - len);
         }
         *SvEND(sv) = '\0';
-
-        /* If there is trailing stuff that couldn't be converted from UTF-8, it
-         * is appended as-is for the ^ and | operators.  This preserves
-         * backwards compatibility */
-        if (right_non_downgraded) {
-            non_downgraded = (char *) right_non_downgraded;
-            non_downgraded_len = right_non_downgraded_len;
-        }
-        else if (left_non_downgraded) {
-            non_downgraded = (char *) left_non_downgraded;
-            non_downgraded_len = left_non_downgraded_len;
-        }
-
         break;
     }
 
     if (result_needs_to_be_utf8) {
         sv_utf8_upgrade_nomg(sv);
-
-        /* Append any trailing UTF-8 as-is. */
-        if (non_downgraded) {
-            sv_catpvn_nomg(sv, non_downgraded, non_downgraded_len);
-        }
     }
 
     SvTAINT(sv);