[PATCH] Improve VRP for sign-changed/widened compares

[Richard Biener <rguenther at suse dot de>]

This improves VRP for cases of

  x = (T) y;
  if (y !=/== CST)
    {
      ... use of X

to insert asserts for X similar to how we handle x = y +- CST.

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

Richard.

2015-06-30  Richard Biener  <rguenther@suse.de>

	* tree-vrp.c (register_edge_assert_for_2): Also register
	asserts for dominating conversion results.

Index: gcc/tree-vrp.c
===================================================================
*** gcc/tree-vrp.c	(revision 225115)
--- gcc/tree-vrp.c	(working copy)
*************** register_edge_assert_for_2 (tree name, e
*** 5359,5365 ****
    /* In the case of post-in/decrement tests like if (i++) ... and uses
       of the in/decremented value on the edge the extra name we want to
       assert for is not on the def chain of the name compared.  Instead
!      it is in the set of use stmts.  */
    if ((comp_code == NE_EXPR
         || comp_code == EQ_EXPR)
        && TREE_CODE (val) == INTEGER_CST)
--- 5359,5367 ----
    /* In the case of post-in/decrement tests like if (i++) ... and uses
       of the in/decremented value on the edge the extra name we want to
       assert for is not on the def chain of the name compared.  Instead
!      it is in the set of use stmts.
!      Similar cases happen for conversions that were simplified through
!      fold_{sign_changed,widened}_comparison.  */
    if ((comp_code == NE_EXPR
         || comp_code == EQ_EXPR)
        && TREE_CODE (val) == INTEGER_CST)
*************** register_edge_assert_for_2 (tree name, e
*** 5368,5396 ****
        gimple use_stmt;
        FOR_EACH_IMM_USE_STMT (use_stmt, ui, name)
  	{
- 	  /* Cut off to use-stmts that are in the predecessor.  */
- 	  if (gimple_bb (use_stmt) != e->src)
- 	    continue;
- 
  	  if (!is_gimple_assign (use_stmt))
  	    continue;
  
! 	  enum tree_code code = gimple_assign_rhs_code (use_stmt);
! 	  if (code != PLUS_EXPR
! 	      && code != MINUS_EXPR)
  	    continue;
  
! 	  tree cst = gimple_assign_rhs2 (use_stmt);
! 	  if (TREE_CODE (cst) != INTEGER_CST)
  	    continue;
  
! 	  tree name2 = gimple_assign_lhs (use_stmt);
! 	  if (live_on_edge (e, name2))
  	    {
  	      cst = int_const_binop (code, val, cst);
- 	      register_new_assert_for (name2, name2, comp_code, cst,
- 				       NULL, e, bsi);
  	    }
  	}
      }
   
--- 5370,5406 ----
        gimple use_stmt;
        FOR_EACH_IMM_USE_STMT (use_stmt, ui, name)
  	{
  	  if (!is_gimple_assign (use_stmt))
  	    continue;
  
! 	  /* Cut off to use-stmts that are dominating the predecessor.  */
! 	  if (!dominated_by_p (CDI_DOMINATORS, e->src, gimple_bb (use_stmt)))
  	    continue;
  
! 	  tree name2 = gimple_assign_lhs (use_stmt);
! 	  if (TREE_CODE (name2) != SSA_NAME
! 	      || !live_on_edge (e, name2))
  	    continue;
  
! 	  enum tree_code code = gimple_assign_rhs_code (use_stmt);
! 	  tree cst;
! 	  if (code == PLUS_EXPR
! 	      || code == MINUS_EXPR)
  	    {
+ 	      cst = gimple_assign_rhs2 (use_stmt);
+ 	      if (TREE_CODE (cst) != INTEGER_CST)
+ 		continue;
  	      cst = int_const_binop (code, val, cst);
  	    }
+ 	  else if (CONVERT_EXPR_CODE_P (code))
+ 	    cst = fold_convert (TREE_TYPE (name2), val);
+ 	  else
+ 	    continue;
+ 
+ 	  if (TREE_OVERFLOW_P (cst))
+ 	    cst = drop_tree_overflow (cst);
+ 	  register_new_assert_for (name2, name2, comp_code, cst,
+ 				   NULL, e, bsi);
  	}
      }