[PATCH][gimplefe] Improve error recovery

[Richard Biener]

Just noticed a few issues when feeding the GIMPLE FE random -gimple
dumps.  On errors not skipping to expected tokens leads to a load
of strange followup parsing errors and worse, to endless parsing
attempts in one case.

Fixed with the following.

Bootstrap / regtest running together with the pass manager change
posted in the other thread.

I consider gimple-parser.c changes like this "middle-end", Joseph,
are you fine with that?

Richard.

2016-12-20  Richard Biener  <rguent...@suse.de>

        c/
        * gimple-parser.c (c_parser_gimple_compound_statement): Improve
        error recovery.
        (c_parser_gimple_statement): Only build assigns for non-error
        stmts.
        (c_parser_gimple_postfix_expression_after): Improve error recovery.

Index: gcc/c/gimple-parser.c
===================================================================
--- gcc/c/gimple-parser.c       (revision 243738)
+++ gcc/c/gimple-parser.c       (working copy)
@@ -215,7 +215,7 @@ c_parser_gimple_compound_statement (c_pa
 expr_stmt:
          c_parser_gimple_statement (parser, seq);
          if (! c_parser_require (parser, CPP_SEMICOLON, "expected %<;%>"))
-           return return_p;
+           c_parser_skip_until_found (parser, CPP_SEMICOLON, NULL);
        }
     }
   c_parser_consume_token (parser);
@@ -327,9 +327,12 @@ c_parser_gimple_statement (c_parser *par
     case CPP_NOT:
     case CPP_MULT: /* pointer deref */
       rhs = c_parser_gimple_unary_expression (parser);
-      assign = gimple_build_assign (lhs.value, rhs.value);
-      gimple_set_location (assign, loc);
-      gimple_seq_add_stmt (seq, assign);
+      if (rhs.value != error_mark_node)
+       {
+         assign = gimple_build_assign (lhs.value, rhs.value);
+         gimple_set_location (assign, loc);
+         gimple_seq_add_stmt (seq, assign);
+       }
       return;
 
     default:;
@@ -385,10 +388,13 @@ c_parser_gimple_statement (c_parser *par
       && lookup_name (c_parser_peek_token (parser)->value))
     {
       rhs = c_parser_gimple_unary_expression (parser);
-      gimple *call = gimple_build_call_from_tree (rhs.value);
-      gimple_call_set_lhs (call, lhs.value);
-      gimple_seq_add_stmt (seq, call);
-      gimple_set_location (call, loc);
+      if (rhs.value != error_mark_node)
+       {
+         gimple *call = gimple_build_call_from_tree (rhs.value);
+         gimple_call_set_lhs (call, lhs.value);
+         gimple_seq_add_stmt (seq, call);
+         gimple_set_location (call, loc);
+       }
       return;
     }
 
@@ -802,7 +808,10 @@ c_parser_gimple_postfix_expression_after
            tree idx = c_parser_gimple_unary_expression (parser).value;
 
            if (! c_parser_require (parser, CPP_CLOSE_SQUARE, "expected %<]%>"))
-             break;
+             {
+               c_parser_skip_until_found (parser, CPP_CLOSE_SQUARE, NULL);
+               break;
+             }
 
            start = expr.get_start ();
            finish = c_parser_tokens_buf (parser, 0)->location;