Re: [PATCH] Fix PR40081, wrong gimple from SRA

[Richard Guenther <rguenther at suse dot de>]

On Sun, 10 May 2009, Richard Guenther wrote:

> On Sun, 10 May 2009, H.J. Lu wrote:
> 
> > On Sun, May 10, 2009 at 3:11 AM, Richard Guenther <rguenther@suse.de> wrote:
> > >
> > > This fixes wrong gimple from SRA created because SRA possibly uses
> > > volatile qualified scalar types as replacements which is obviously
> > > bogus (and at least a missed optimization, but in this case causing
> > > invalid gimple). ?The problem is latent since ever, thus I plan
> > > only to fix the trunk and 4.4.
> > >
> > > Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
> > > Also tested on the 4.4 branch, queued for applying there.
> > >
> > > Richard.
> > >
> > > 2009-05-10 ?Richard Guenther ?<rguenther@suse.de>
> > >
> > > ? ? ? ?PR tree-optimization/40081
> > > ? ? ? ?* tree-sra.c (instantiate_element): Instantiate scalar replacements
> > > ? ? ? ?using the main variant of the element type. ?Do not fiddle with
> > > ? ? ? ?TREE_THIS_VOLATILE or TREE_SIDE_EFFECTS.
> > >
> > > ? ? ? ?* g++.dg/torture/pr40081.C: New testcase.
> > >
> > >
> > 
> > This caused:
> > 
> > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40090
> 
> Huh, I didn't see those.  But I am already testing a different fix
> for probably the same reason.

Here it is.  Punt on structures with volatile fields.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to
trunk.

Richard.

2009-05-10  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/40081
	Revert
	* tree-sra.c (instantiate_element): Instantiate scalar replacements
	using the main variant of the element type.  Do not fiddle with
	TREE_THIS_VOLATILE or TREE_SIDE_EFFECTS.

	* tree-sra.c (sra_type_can_be_decomposed_p): Do not decompose
	structs with volatile fields.

Index: gcc/tree-sra.c
===================================================================
*** gcc/tree-sra.c	(revision 147330)
--- gcc/tree-sra.c	(working copy)
*************** sra_type_can_be_decomposed_p (tree type)
*** 270,275 ****
--- 270,279 ----
  		      != TYPE_PRECISION (TREE_TYPE (t))))
  		goto fail;
  
+ 	      /* And volatile fields.  */
+ 	      if (TREE_THIS_VOLATILE (t))
+ 		goto fail;
+ 
  	      saw_one_field = true;
  	    }
  
*************** instantiate_element (struct sra_elt *elt
*** 1277,1284 ****
        nowarn = TREE_NO_WARNING (base_elt->parent->element);
    base = base_elt->element;
  
!   elt->replacement = var = make_rename_temp (TYPE_MAIN_VARIANT (elt->type),
! 					     "SR");
  
    if (DECL_P (elt->element)
        && !tree_int_cst_equal (DECL_SIZE (var), DECL_SIZE (elt->element)))
--- 1281,1287 ----
        nowarn = TREE_NO_WARNING (base_elt->parent->element);
    base = base_elt->element;
  
!   elt->replacement = var = make_rename_temp (elt->type, "SR");
  
    if (DECL_P (elt->element)
        && !tree_int_cst_equal (DECL_SIZE (var), DECL_SIZE (elt->element)))
*************** instantiate_element (struct sra_elt *elt
*** 1287,1294 ****
        DECL_SIZE_UNIT (var) = DECL_SIZE_UNIT (elt->element);
  
        elt->in_bitfld_block = 1;
!       elt->replacement = fold_build3 (BIT_FIELD_REF,
! 				      TYPE_MAIN_VARIANT (elt->type), var,
  				      DECL_SIZE (var),
  				      BYTES_BIG_ENDIAN
  				      ? size_binop (MINUS_EXPR,
--- 1290,1296 ----
        DECL_SIZE_UNIT (var) = DECL_SIZE_UNIT (elt->element);
  
        elt->in_bitfld_block = 1;
!       elt->replacement = fold_build3 (BIT_FIELD_REF, elt->type, var,
  				      DECL_SIZE (var),
  				      BYTES_BIG_ENDIAN
  				      ? size_binop (MINUS_EXPR,
*************** instantiate_element (struct sra_elt *elt
*** 1305,1310 ****
--- 1307,1318 ----
    DECL_SOURCE_LOCATION (var) = DECL_SOURCE_LOCATION (base);
    DECL_ARTIFICIAL (var) = 1;
  
+   if (TREE_THIS_VOLATILE (elt->type))
+     {
+       TREE_THIS_VOLATILE (var) = 1;
+       TREE_SIDE_EFFECTS (var) = 1;
+     }
+ 
    if (DECL_NAME (base) && !DECL_IGNORED_P (base))
      {
        char *pretty_name = build_element_name (elt);