[Patch, fortran] PR61138 Wrong code with pointer-bounds remapping

[Mikael Morin]

Hello,

this is about a pointer bounds remapping regression introduced at
http://gcc.gnu.org/r190641
That revision introduced support for se.descriptor_only in
gfc_conv_expr_descriptor with this hunk:

> Index: trans-array.c
> ===================================================================
> --- trans-array.c	(révision 220514)
> +++ trans-array.c	(copie de travail)
> @@ -6574,7 +6574,7 @@ gfc_conv_expr_descriptor (gfc_se *se, gfc_expr *ex
>  	  /* Create a new descriptor if the array doesn't have one.  */
>  	  full = 0;
>  	}
> -      else if (info->ref->u.ar.type == AR_FULL)
> +      else if (info->ref->u.ar.type == AR_FULL || se->descriptor_only)
>  	full = 1;
>        else if (se->direct_byref)
>  	full = 0;

The problem comes from gfc_trans_pointer_assign, which uses several
times the same gfc_se struct, the first time with descriptor_only set,
the other times without clearing it.
This was not a problem before the above change, because the flag wasn't
looked at.
After the change however, one should make sure that descriptor_only is
not inherited from a previous use.

The fix proposed clears the flag upon reuse, which should match exactly
the original behaviour, making it rather safe, and suitable also for the
branches.
I have to admit that I'm not completely satisfied with it however.
I would prefer no GFC_SE reuse at all, namely collect every piece of
code in a separate struct, and merge them later explicitly into a block.
 Alas, the code is not exactly straightforward to my eyes, and my
attempt in that direction to sneak some orthogonality in that madness
failed.

Anyway, regression tested on x86_64-linux, OK for trunk/4.9/4.8 ?

Mikael
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2015-02-09  Mikael Morin  <mikael@gcc.gnu.org>

	PR fortran/61138
	* trans-expr.c (gfc_trans_pointer_assignment): Clear DESCRIPTOR_ONLY
	field before reusing LSE.

2015-02-09  Mikael Morin  <mikael@gcc.gnu.org>

	PR fortran/61138
	gfortran.dg/pointer_remapping_9.f90: New.
	
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