[PATCH] Fix PR26135, store copyprop being not effective

[Richard Guenther <rguenther at suse dot de>]

This adds the missing parts to the copyprop implementation to do store
copyprop.

Bootstrapped and tested on x86_64-unknown-linux-gnu, plain and with
-fno-tree-dominator-opts (as most store copyprop opportunities are
already handled by DOM).

Ok for mainline?

Thanks,
Richard.


2006-02-07  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-copy.c (stmt_may_generate_copy): Handle memory
	loads for store copy-prop.
	(copy_prop_visit_stmt): Likewise.

	* gcc.dg/tree-ssa/ssa-copyprop-1.c: New testcase.

Index: tree-ssa-copy.c
===================================================================
*** tree-ssa-copy.c	(revision 110646)
--- tree-ssa-copy.c	(working copy)
*************** stmt_may_generate_copy (tree stmt)
*** 376,382 ****
    /* Otherwise, the only statements that generate useful copies are
       assignments whose RHS is just an SSA name that doesn't flow
       through abnormal edges.  */
!   return TREE_CODE (rhs) == SSA_NAME && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs);
  }
  
  
--- 376,385 ----
    /* Otherwise, the only statements that generate useful copies are
       assignments whose RHS is just an SSA name that doesn't flow
       through abnormal edges.  */
!   return (do_store_copy_prop
! 	  && TREE_CODE (lhs) == SSA_NAME)
! 	 || (TREE_CODE (rhs) == SSA_NAME
! 	     && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs));
  }
  
  
*************** copy_prop_visit_stmt (tree stmt, edge *t
*** 692,697 ****
--- 695,728 ----
  	 see if the lattice value of its output has changed.  */
        retval = copy_prop_visit_assignment (stmt, result_p);
      }
+   else if (TREE_CODE (stmt) == MODIFY_EXPR
+ 	   && TREE_CODE (TREE_OPERAND (stmt, 0)) == SSA_NAME
+ 	   && do_store_copy_prop
+ 	   && stmt_makes_single_load (stmt))
+     {
+       /* If the statement is a copy assignment with a memory load
+ 	 on the RHS, see if we know the value of this load and
+ 	 update the lattice accordingly.  */
+       prop_value_t *val = get_value_loaded_by (stmt, copy_of);
+       if (val
+ 	  && val->mem_ref
+ 	  && is_gimple_reg (val->value)
+ 	  && operand_equal_p (val->mem_ref, TREE_OPERAND (stmt, 1), 0))
+         {
+ 	  bool changed;
+ 	  changed = set_copy_of_val (TREE_OPERAND (stmt, 0),
+ 				     val->value, val->mem_ref);
+ 	  if (changed)
+ 	    {
+ 	      *result_p = TREE_OPERAND (stmt, 0);
+ 	      retval = SSA_PROP_INTERESTING;
+ 	    }
+ 	  else
+ 	    retval = SSA_PROP_NOT_INTERESTING;
+ 	}
+       else
+         retval = SSA_PROP_VARYING;
+     }
    else if (TREE_CODE (stmt) == COND_EXPR)
      {
        /* See if we can determine which edge goes out of a conditional
Index: testsuite/gcc.dg/tree-ssa/ssa-copyprop-1.c
===================================================================
*** testsuite/gcc.dg/tree-ssa/ssa-copyprop-1.c	(revision 0)
--- testsuite/gcc.dg/tree-ssa/ssa-copyprop-1.c	(revision 0)
***************
*** 0 ****
--- 1,12 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O2 -fno-tree-dominator-opts -fdump-tree-store_copyprop-details" } */
+ 
+ typedef struct { int i; int j; } A;
+ int foo(A *a, int i)
+ {
+   a->i = i;
+   return a->i;
+ }
+ 
+ /* { dg-final { scan-tree-dump "return i" "store_copyprop" } } */
+ /* { dg-final { cleanup-tree-dump "store_copyprop" } } */