Re: [PATCH] Fix up creation of lowpart subregs in valtrack (PR debug/65678)

[Richard Biener <rguenther@suse.de>]

On Tue, 7 Apr 2015, Jakub Jelinek wrote:

> Hi!
> 
> gen_rtx_SUBREG/gen_lowpart_SUBREG ICE when trying to create a subreg
> the backend doesn't like, lowpart_subreg returns NULL.  But, for debug info
> purposes, all lowpart subregs are valid, a subreg in the debug insns or
> var-tracking notes is simply a mode punning construct, and even when the
> backend doesn't have any instruction to perform such operation, the debugger
> can always do the punning.
> 
> var-tracking.c already has code to emit gen_rtx_raw_SUBREG if everything
> else fails, the following patch adjusts valtrack.c to do the same thing.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Ok.

Thanks,
Richard.

> 2015-04-07  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR debug/65678
> 	* valtrack.c (debug_lowpart_subreg): New function.
> 	(dead_debug_insert_temp): Use it.
> 
> 	* g++.dg/debug/pr65678.C: New test.
> 
> --- gcc/valtrack.c.jj	2015-01-05 13:07:14.000000000 +0100
> +++ gcc/valtrack.c	2015-04-07 11:10:36.045912355 +0200
> @@ -534,6 +534,22 @@ dead_debug_add (struct dead_debug_local
>    bitmap_set_bit (debug->used, uregno);
>  }
>  
> +/* Like lowpart_subreg, but if a subreg is not valid for machine, force
> +   it anyway - for use in debug insns.  */
> +
> +static rtx
> +debug_lowpart_subreg (machine_mode outer_mode, rtx expr,
> +		      machine_mode inner_mode)
> +{
> +  if (inner_mode == VOIDmode)
> +    inner_mode = GET_MODE (expr);
> +  int offset = subreg_lowpart_offset (outer_mode, inner_mode);
> +  rtx ret = simplify_gen_subreg (outer_mode, expr, inner_mode, offset);
> +  if (ret)
> +    return ret;
> +  return gen_rtx_raw_SUBREG (outer_mode, expr, offset);
> +}
> +
>  /* If UREGNO is referenced by any entry in DEBUG, emit a debug insn
>     before or after INSN (depending on WHERE), that binds a (possibly
>     global) debug temp to the widest-mode use of UREGNO, if WHERE is
> @@ -662,9 +678,9 @@ dead_debug_insert_temp (struct dead_debu
>  	  /* Ok, it's the same (hardware) REG, but with a different
>  	     mode, so SUBREG it.  */
>  	  else
> -	    breg = lowpart_subreg (GET_MODE (reg),
> -				   cleanup_auto_inc_dec (src, VOIDmode),
> -				   GET_MODE (dest));
> +	    breg = debug_lowpart_subreg (GET_MODE (reg),
> +					 cleanup_auto_inc_dec (src, VOIDmode),
> +					 GET_MODE (dest));
>  	}
>        else if (GET_CODE (dest) == SUBREG)
>  	{
> @@ -684,9 +700,9 @@ dead_debug_insert_temp (struct dead_debu
>  	    breg = NULL;
>  	  /* Yay, we can use SRC, just adjust its mode.  */
>  	  else
> -	    breg = lowpart_subreg (GET_MODE (reg),
> -				   cleanup_auto_inc_dec (src, VOIDmode),
> -				   GET_MODE (dest));
> +	    breg = debug_lowpart_subreg (GET_MODE (reg),
> +					 cleanup_auto_inc_dec (src, VOIDmode),
> +					 GET_MODE (dest));
>  	}
>        /* Oh well, we're out of luck.  */
>        else
> @@ -740,7 +756,8 @@ dead_debug_insert_temp (struct dead_debu
>  	*DF_REF_REAL_LOC (cur->use) = dval;
>        else
>  	*DF_REF_REAL_LOC (cur->use)
> -	  = gen_lowpart_SUBREG (GET_MODE (*DF_REF_REAL_LOC (cur->use)), dval);
> +	  = debug_lowpart_subreg (GET_MODE (*DF_REF_REAL_LOC (cur->use)), dval,
> +				  GET_MODE (dval));
>        /* ??? Should we simplify subreg of subreg?  */
>        bitmap_set_bit (debug->to_rescan, INSN_UID (DF_REF_INSN (cur->use)));
>        uses = cur->next;
> --- gcc/testsuite/g++.dg/debug/pr65678.C.jj	2015-04-07 11:18:51.701891845 +0200
> +++ gcc/testsuite/g++.dg/debug/pr65678.C	2015-04-07 11:19:50.285943861 +0200
> @@ -0,0 +1,35 @@
> +// PR debug/65678
> +// { dg-do compile }
> +
> +long long v;
> +
> +static int
> +bar (double x)
> +{
> +#if __SIZEOF_DOUBLE__ == __SIZEOF_LONG_LONG__
> +  __builtin_memmove (&v, &x, sizeof v);
> +#else
> +  (void) x;
> +  v = 0;
> +#endif
> +  return v;
> +}
> +
> +struct A
> +{
> +  A (double x) : a (bar (x)) {}
> +  int m1 ();
> +  int m2 () { int b = a; return b; }
> +  int a;
> +};
> +
> +void foo ();
> +
> +void
> +baz (double x)
> +{
> +  int c = A (x).m2 ();
> +  int d = A (x).m1 ();
> +  if (d)
> +    foo ();
> +}
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Jennifer Guild,
Dilip Upmanyu, Graham Norton HRB 21284 (AG Nuernberg)