[PATCH] Fix PR34148 a bit

[Richard Guenther <rguenther@suse.de>]

This fixes the huge memory and compile-time regression on qmake files
by noting that it is pointless to generate SFTs for single-element 
structures (and thus in this case unpartitionable SFTs).

This reduces compile-time and memory-usage from >1.5GB and (no idea, 
>2min) to <200MB and 20s.

Another possible optimization I'll post/test seperately is to only
treat SFT_UNPARTITIONABLE_P as non-partitionable if they are (still)
addressable.

Bootstrap & regtest on x86_64-unknown-linux-gnu running, I'll apply
this if it succeeds.

Richard.


2007-11-20  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/34148
	* tree-ssa-structalias.c (create_variable_info_for): Do not use
	field-sensitive PTA for single-element structures.
	* tree-ssa-alias.c (create_overlap_variables_for): Do not create
	SFTs for single-element structures.

Index: tree-ssa-structalias.c
===================================================================
*** tree-ssa-structalias.c	(revision 130288)
--- tree-ssa-structalias.c	(working copy)
*************** create_variable_info_for (tree decl, con
*** 4441,4446 ****
--- 4441,4447 ----
        && !notokay
        && !vi->is_unknown_size_var
        && var_can_have_subvars (decl)
+       && VEC_length (fieldoff_s, fieldstack) > 1
        && VEC_length (fieldoff_s, fieldstack) <= MAX_FIELDS_FOR_FIELD_SENSITIVE)
      {
        unsigned int newindex = VEC_length (varinfo_t, varmap);
Index: tree-ssa-alias.c
===================================================================
*** tree-ssa-alias.c	(revision 130288)
--- tree-ssa-alias.c	(working copy)
*************** create_overlap_variables_for (tree var)
*** 3837,3843 ****
  			       TREE_TYPE (var));
    /* Make sure to not create SFTs for structs we won't generate variable
       infos for.  See tree-ssa-structalias.c:create_variable_info_for ().  */
!   if (VEC_length (fieldoff_s, fieldstack) != 0
        && VEC_length (fieldoff_s, fieldstack) <= MAX_FIELDS_FOR_FIELD_SENSITIVE)
      {
        subvar_t *subvars;
--- 3837,3843 ----
  			       TREE_TYPE (var));
    /* Make sure to not create SFTs for structs we won't generate variable
       infos for.  See tree-ssa-structalias.c:create_variable_info_for ().  */
!   if (VEC_length (fieldoff_s, fieldstack) > 1
        && VEC_length (fieldoff_s, fieldstack) <= MAX_FIELDS_FOR_FIELD_SENSITIVE)
      {
        subvar_t *subvars;