[PATCH] Fix PR68240

[PATCH] Fix PR68240

[Richard Biener]

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

Richard.

2015-11-10  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/68240
	* tree-ssa-sccvn.c (cond_stmts_equal_p): Handle commutative compares
	properly.
	(visit_phi): For PHIs with just a single executable edge
	take its value directly.
	(expressions_equal_p): Handle VN_TOP properly.

	* gcc.dg/torture/pr68240.c: New testcase.

Index: gcc/testsuite/gcc.dg/torture/pr68240.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr68240.c	(revision 0)
--- gcc/testsuite/gcc.dg/torture/pr68240.c	(working copy)
***************
*** 0 ****
--- 1,12 ----
+ /* { dg-do compile } */
+ 
+ int a, b, f;
+ 
+ void
+ fn1 ()
+ {
+   int c = 1, d, e = 1;
+   a = 1; 
+   for (; f;)
+     b = (c && (d = (e && a)));
+ }
Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c	(revision 230020)
--- gcc/tree-ssa-sccvn.c	(working copy)
*************** cond_stmts_equal_p (gcond *cond1, gcond
*** 2760,2770 ****
    else
      return false;
  
!   if (! expressions_equal_p (vn_valueize (lhs1), vn_valueize (lhs2))
!       || ! expressions_equal_p (vn_valueize (rhs1), vn_valueize (rhs2)))
!     return false;
! 
!   return true;
  }
  
  /* Compare two phi entries for equality, ignoring VN_TOP arguments.  */
--- 2806,2820 ----
    else
      return false;
  
!   lhs1 = vn_valueize (lhs1);
!   rhs1 = vn_valueize (rhs1);
!   lhs2 = vn_valueize (lhs2);
!   rhs2 = vn_valueize (rhs2);
!   return ((expressions_equal_p (lhs1, lhs2)
! 	   && expressions_equal_p (rhs1, rhs2))
! 	  || (commutative_tree_code (code1)
! 	      && expressions_equal_p (lhs1, rhs2)
! 	      && expressions_equal_p (rhs1, lhs2)));
  }
  
  /* Compare two phi entries for equality, ignoring VN_TOP arguments.  */
*************** visit_phi (gimple *phi)
*** 3379,3384 ****
--- 3428,3434 ----
    tree result;
    tree sameval = VN_TOP;
    bool allsame = true;
+   unsigned n_executable = 0;
  
    /* TODO: We could check for this in init_sccvn, and replace this
       with a gcc_assert.  */
*************** visit_phi (gimple *phi)
*** 3394,3399 ****
--- 3444,3450 ----
        {
  	tree def = PHI_ARG_DEF_FROM_EDGE (phi, e);
  
+ 	++n_executable;
  	if (TREE_CODE (def) == SSA_NAME)
  	  def = SSA_VAL (def);
  	if (def == VN_TOP)
*************** visit_phi (gimple *phi)
*** 3408,3416 ****
        }
    
    /* If none of the edges was executable or all incoming values are
!      undefined keep the value-number at VN_TOP.  */
!   if (sameval == VN_TOP)
!     return set_ssa_val_to (PHI_RESULT (phi), VN_TOP);
  
    /* First see if it is equivalent to a phi node in this block.  We prefer
       this as it allows IV elimination - see PRs 66502 and 67167.  */
--- 3459,3469 ----
        }
    
    /* If none of the edges was executable or all incoming values are
!      undefined keep the value-number at VN_TOP.  If only a single edge
!      is exectuable use its value.  */
!   if (sameval == VN_TOP
!       || n_executable == 1)
!     return set_ssa_val_to (PHI_RESULT (phi), sameval);
  
    /* First see if it is equivalent to a phi node in this block.  We prefer
       this as it allows IV elimination - see PRs 66502 and 67167.  */
*************** expressions_equal_p (tree e1, tree e2)
*** 4610,4615 ****
--- 4663,4672 ----
    if (e1 == e2)
      return true;
  
+   /* If either one is VN_TOP consider them equal.  */
+   if (e1 == VN_TOP || e2 == VN_TOP)
+     return true;
+ 
    /* If only one of them is null, they cannot be equal.  */
    if (!e1 || !e2)
      return false;