[PATCH] Fix PR38051, alias partitioning related problem

[Richard Guenther]

On Sat, 15 Nov 2008, Richard Guenther wrote:

> 
> When partitioning partitions a variable in a second alias pass we
> miss to consider that variable as written to because we ask the
> stored_syms bitmap which only contains the MPT.  This causes us
> to disregard the variable for conflicts.
> 
> Fixed with the following - we can just look up the LHS decl ourselves.
> Memory tags are marked as written by the pointer setup code, calls
> and asms are handled by the fact that when we check the written
> variables we also check the call clobber set.
> 
> Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
> 
> This problem is latent on the branch, but as a backport is non-trivial
> I will not do it at this point.

PR38169 and some backports made it necessary that I fix this for the
branch as well.  So here's the backport.

Bootstrapped and tested on x86_64-unknown-linux-gnu.  I'll give this
more testing before applying it.

Richard.

2008-11-17  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/38051
	* tree-ssa-structalias.c (update_alias_info): Manually find
	written variables.

Index: gcc/tree-ssa-structalias.c
===================================================================
*** gcc/tree-ssa-structalias.c	(revision 141900)
--- gcc/tree-ssa-structalias.c	(working copy)
*************** update_alias_info (tree stmt, struct ali
*** 3467,3472 ****
--- 3467,3495 ----
  
        mem_ref_stats->num_mem_stmts++;
  
+       /* Add all decls written to to the list of written variables.  */
+       if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+ 	  && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 0)) != SSA_NAME)
+ 	{
+ 	  tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
+ 	  while (handled_component_p (lhs))
+ 	    lhs = TREE_OPERAND (lhs, 0);
+ 	  if (DECL_P (lhs))
+ 	    {
+ 	      subvar_t svars;
+ 	      if (var_can_have_subvars (lhs)
+ 		  && (svars = get_subvars_for_var (lhs)))
+ 		{
+ 		  unsigned int i;
+ 		  tree subvar;
+ 		  for (i = 0; VEC_iterate (tree, svars, i, subvar); ++i)
+ 		    pointer_set_insert (ai->written_vars, subvar);
+ 		}
+ 	      else
+ 		pointer_set_insert (ai->written_vars, lhs);
+ 	    }
+ 	}
+ 
        /* Notice that we only update memory reference stats for symbols
  	 loaded and stored by the statement if the statement does not
  	 contain pointer dereferences and it is not a call/asm site.
*************** update_alias_info (tree stmt, struct ali
*** 3489,3513 ****
  	 dereferences (e.g., MEMORY_VAR = *PTR) or if a call site has
  	 memory symbols in its argument list, but these cases do not
  	 occur so frequently as to constitute a serious problem.  */
-       if (STORED_SYMS (stmt))
- 	EXECUTE_IF_SET_IN_BITMAP (STORED_SYMS (stmt), 0, i, bi)
- 	  {
- 	    tree sym = referenced_var (i);
- 	    pointer_set_insert (ai->written_vars, sym);
- 	    if (!stmt_dereferences_ptr_p
- 		&& stmt_escape_type != ESCAPE_TO_CALL
- 		&& stmt_escape_type != ESCAPE_TO_PURE_CONST
- 		&& stmt_escape_type != ESCAPE_TO_ASM)
- 	      update_mem_sym_stats_from_stmt (sym, stmt, 0, 1);
- 	  }
- 
        if (!stmt_dereferences_ptr_p
- 	  && LOADED_SYMS (stmt)
  	  && stmt_escape_type != ESCAPE_TO_CALL
  	  && stmt_escape_type != ESCAPE_TO_PURE_CONST
  	  && stmt_escape_type != ESCAPE_TO_ASM)
! 	EXECUTE_IF_SET_IN_BITMAP (LOADED_SYMS (stmt), 0, i, bi)
! 	  update_mem_sym_stats_from_stmt (referenced_var (i), stmt, 1, 0);
      }
  }
  
--- 3512,3530 ----
  	 dereferences (e.g., MEMORY_VAR = *PTR) or if a call site has
  	 memory symbols in its argument list, but these cases do not
  	 occur so frequently as to constitute a serious problem.  */
        if (!stmt_dereferences_ptr_p
  	  && stmt_escape_type != ESCAPE_TO_CALL
  	  && stmt_escape_type != ESCAPE_TO_PURE_CONST
  	  && stmt_escape_type != ESCAPE_TO_ASM)
! 	{
! 	  if (STORED_SYMS (stmt))
! 	    EXECUTE_IF_SET_IN_BITMAP (STORED_SYMS (stmt), 0, i, bi)
! 	      update_mem_sym_stats_from_stmt (referenced_var (i), stmt, 0, 1);
! 
! 	  if (LOADED_SYMS (stmt))
! 	    EXECUTE_IF_SET_IN_BITMAP (LOADED_SYMS (stmt), 0, i, bi)
! 	      update_mem_sym_stats_from_stmt (referenced_var (i), stmt, 1, 0);
! 	}
      }
  }