Regression for gcc.dg/Wstrict-overflow-11.c between 124216:124219

[Richard Guenther]

On Fri, 27 Apr 2007, Richard Guenther wrote:

> On 4/27/07, Hans-Peter Nilsson <hans-peter.nilsson@axis.com> wrote:
> > Something in your
> > +       PR tree-optimization/30965
> > +       PR tree-optimization/30978
> >
> > fix caused a regression for gcc.dg/Wstrict-overflow-11.c (for
> > cris-elf, but that shouldn't matter):
> 
> Well, loop header copying introduces a comparison that is always true:
> 
> <bb 2>:
>  D.1630_13 = i_4(D) + 4;
>  if (i_4(D) <= D.1630_13)
>    goto <bb 3> (<L0>);
>  else
>    goto <bb 4> (<L2>);
> 
> and before this patch we were not able to fold this.  Now we do and
> get this warning.
> 
> Which makes me think again that all "compiler generated" code should
> have TREE_NO_WARNING set.  Or, Ian, any idea on how to fix _this_
> warning but not warnings from forwprop in general?

So the following fixes it.  I'll give it the testing later.

Richard.

2007-04-27  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-forwprop.c (forward_propagate_into_cond): Keep track
	if we simplified anything.
	(tree_ssa_forward_propagate_single_use_vars): Defer overflow
	warnings until we did a simplification and the stmt was not
	marked as TREE_NO_WARNING.

Index: tree-ssa-forwprop.c
===================================================================
*** tree-ssa-forwprop.c	(revision 124226)
--- tree-ssa-forwprop.c	(working copy)
*************** combine_cond_expr_cond (enum tree_code c
*** 372,380 ****
  /* Propagate from the ssa name definition statements of COND_EXPR
     in statement STMT into the conditional if that simplifies it.  */
  
! static void
  forward_propagate_into_cond (tree cond_expr, tree stmt)
  {
    do {
      tree tmp = NULL_TREE;
      tree cond = COND_EXPR_COND (cond_expr);
--- 372,382 ----
  /* Propagate from the ssa name definition statements of COND_EXPR
     in statement STMT into the conditional if that simplifies it.  */
  
! static bool
  forward_propagate_into_cond (tree cond_expr, tree stmt)
  {
+   bool did_something = false;
+ 
    do {
      tree tmp = NULL_TREE;
      tree cond = COND_EXPR_COND (cond_expr);
*************** forward_propagate_into_cond (tree cond_e
*** 407,413 ****
  	    def_stmt = get_prop_source_stmt (name, false, &single_use_p);
  	    if (def_stmt == NULL_TREE
  	        || !can_propagate_from (def_stmt))
! 	      return;
  
  	    rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
  	    tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
--- 409,415 ----
  	    def_stmt = get_prop_source_stmt (name, false, &single_use_p);
  	    if (def_stmt == NULL_TREE
  	        || !can_propagate_from (def_stmt))
! 	      return did_something;
  
  	    rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
  	    tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
*************** forward_propagate_into_cond (tree cond_e
*** 422,428 ****
  	def_stmt = get_prop_source_stmt (name, true, NULL);
  	if (def_stmt == NULL_TREE
  	    || !can_propagate_from (def_stmt))
! 	  return;
  
  	rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
  	tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs,
--- 424,430 ----
  	def_stmt = get_prop_source_stmt (name, true, NULL);
  	if (def_stmt == NULL_TREE
  	    || !can_propagate_from (def_stmt))
! 	  return did_something;
  
  	rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
  	tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs,
*************** forward_propagate_into_cond (tree cond_e
*** 447,458 ****
--- 449,464 ----
  	/* Remove defining statements.  */
  	remove_prop_source_from_use (name, NULL);
  
+ 	did_something = true;
+ 
  	/* Continue combining.  */
  	continue;
        }
  
      break;
    } while (1);
+ 
+   return did_something;
  }
  
  /* We've just substituted an ADDR_EXPR into stmt.  Update all the 
*************** tree_ssa_forward_propagate_single_use_va
*** 986,992 ****
  		}
                else if (TREE_CODE (rhs) == COND_EXPR)
                  {
!                   forward_propagate_into_cond (rhs, stmt);
  		  bsi_next (&bsi);
                  }
  	      else if (COMPARISON_CLASS_P (rhs))
--- 992,1002 ----
  		}
                else if (TREE_CODE (rhs) == COND_EXPR)
                  {
! 		  bool did_something;
! 		  fold_defer_overflow_warnings ();
!                   did_something = forward_propagate_into_cond (rhs, stmt);
! 		  fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs)
! 		    && did_something, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
  		  bsi_next (&bsi);
                  }
  	      else if (COMPARISON_CLASS_P (rhs))
*************** tree_ssa_forward_propagate_single_use_va
*** 1010,1016 ****
  	    }
  	  else if (TREE_CODE (stmt) == COND_EXPR)
  	    {
! 	      forward_propagate_into_cond (stmt, stmt);
  	      bsi_next (&bsi);
  	    }
  	  else
--- 1020,1031 ----
  	    }
  	  else if (TREE_CODE (stmt) == COND_EXPR)
  	    {
! 	      bool did_something;
! 	      fold_defer_overflow_warnings ();
! 	      did_something = forward_propagate_into_cond (stmt, stmt);
! 	      fold_undefer_overflow_warnings (!TREE_NO_WARNING (stmt)
! 					      && did_something, stmt,
! 					      WARN_STRICT_OVERFLOW_CONDITIONAL);
  	      bsi_next (&bsi);
  	    }
  	  else