Re: [PATCH] Fix lots of uninitialized memory uses in sched_analyze_reg

[Vladimir Makarov <vmakarov at redhat dot com>]

On 13-03-04 4:17 PM, Jakub Jelinek wrote:
> Hi!
>
> Something that again hits lots of testcases during valgrind checking
> bootstrap.  init_alias_analysis apparently does
>    vec_safe_grow_cleared (reg_known_value, maxreg - FIRST_PSEUDO_REGISTER);
>    reg_known_equiv_p = sbitmap_alloc (maxreg - FIRST_PSEUDO_REGISTER);
> but doesn't bitmap_clear (reg_known_equiv_p), perhaps as an optimization?
Sorry, I don't know current state of alias.c well to say something 
definite about this.  But I believe it should be cleared.
> If set_reg_known_value is called (and not to the reg itself),
> set_reg_known_equiv_p is called too though.
> Right now get_reg_known_equiv_p is only called in one place, and we are only
> interested in MEM_P known values there, so the following works fine.
> Though perhaps if in the future we use the reg_known_equiv_p bitmap more,
> we should bitmap_clear (reg_known_equiv_p) it instead.
> Bootstrapped/regtested on x86_64-linux and i686-linux.
>
> Ok for trunk (or do you prefer to slow down init_alias_analysis and just
> clear the bitmap)?
I don't see any harm from your patch but I guess it should be fixed by 
clearing reg_know_equiv_p.  I think you need Steven's opinion on this as 
he is an author of the code.
> 2013-03-04  Jakub Jelinek  <jakub@redhat.com>
>
> 	* sched-deps.c (sched_analyze_reg): Only call get_reg_known_equiv_p
> 	if get_reg_known_value returned non-NULL.
>
> --- gcc/sched-deps.c.jj	2013-03-04 12:21:09.000000000 +0100
> +++ gcc/sched-deps.c	2013-03-04 17:29:03.478944157 +0100
> @@ -2351,10 +2351,10 @@ sched_analyze_reg (struct deps_desc *dep
>         /* Pseudos that are REG_EQUIV to something may be replaced
>   	 by that during reloading.  We need only add dependencies for
>   	the address in the REG_EQUIV note.  */
> -      if (!reload_completed && get_reg_known_equiv_p (regno))
> +      if (!reload_completed)
>   	{
>   	  rtx t = get_reg_known_value (regno);
> -	  if (MEM_P (t))
> +	  if (t && MEM_P (t) && get_reg_known_equiv_p (regno))
>   	    sched_analyze_2 (deps, XEXP (t, 0), insn);
>   	}
>