Re: [PATCH] gcc/reload.c: Initialize several arrays before use them in find_reloads()

[Jeff Law <law at redhat dot com>]

On 02/22/15 02:02, Chen Gang S wrote:
> It is for Bug65117, after this fix, ".i" file can be passed compiling.
>
>    - 'this_alternative_win' is not initialized before use it: for the
>      first looping 0, it initializes 'this_alternative_win[0]', but
>      'did_match' may use 'this_alternative_win[2]'.
>
>    - 'this_alternative' may be not initialized before using: it
>      initializes 'this_alternative[i]', but may use 'this_alternative[m]'
>      (m > i).
>
>    - After reading through the code, arrays 'this_alternative_match_win',
>      'this_alternative_offmemok', and 'this_alternative_earlyclobber' may
>      be not initialized either, so initialize them too.
>
> This issue is found by cross compiling xtensa Linux kernel with the
> latest gcc5. And after this patch, it can cross compile xtensa Linux
> kernel with allmodconfig, successfully.
>
>
> 2015-02-22  Chen Gang  <gang.chen.5i5j@gmail.com>
>
> 	* reload.c (find_reloads): Initialize several arrays before use
> 	them.

From the documentation for matching constraints:

  Moreover, the digit must be a
  smaller number than the number of the operand that uses it in the
  constraint.


If we look at the zero_cost_loop_{start,end} patterns we have:

        (if_then_else (ne (match_operand:SI 0 "register_operand" "2")

and


        (if_then_else (ne (match_operand:SI 0 "nonimmediate_operand" "2,2")

Similarly for the loop_end pattern.


Which violate the rule for matching constraints.

I'm confident that if the xtensa's patterns were fixed to abide by the 
rules for matching constraints the problem in reload would not occur.

jeff