[PATCH] Fix PR78644

[Richard Biener <rguenther at suse dot de>]

I am testing the following patch that avoids putting non-final copies
into the CCP lattice which eventually results in released SSA names in
the IL.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2017-03-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/78644
	* tree-ssa-ccp.c (evaluate_stmt): When we may not use the value
	of a simplification result we may not use it at all.

	* gcc.dg/pr78644-1.c: New testcase.
	* gcc.dg/pr78644-2.c: Likewise.

Index: gcc/tree-ssa-ccp.c
===================================================================
*** gcc/tree-ssa-ccp.c	(revision 246527)
--- gcc/tree-ssa-ccp.c	(working copy)
*************** evaluate_stmt (gimple *stmt)
*** 1749,1766 ****
        fold_defer_overflow_warnings ();
        simplified = ccp_fold (stmt);
        if (simplified
! 	  && TREE_CODE (simplified) == SSA_NAME
  	  /* We may not use values of something that may be simulated again,
  	     see valueize_op_1.  */
! 	  && (SSA_NAME_IS_DEFAULT_DEF (simplified)
! 	      || ! prop_simulate_again_p (SSA_NAME_DEF_STMT (simplified))))
! 	{
! 	  ccp_prop_value_t *val = get_value (simplified);
! 	  if (val && val->lattice_val != VARYING)
  	    {
! 	      fold_undefer_overflow_warnings (true, stmt, 0);
! 	      return *val;
  	    }
  	}
        is_constant = simplified && is_gimple_min_invariant (simplified);
        fold_undefer_overflow_warnings (is_constant, stmt, 0);
--- 1749,1772 ----
        fold_defer_overflow_warnings ();
        simplified = ccp_fold (stmt);
        if (simplified
! 	  && TREE_CODE (simplified) == SSA_NAME)
! 	{
  	  /* We may not use values of something that may be simulated again,
  	     see valueize_op_1.  */
! 	  if (SSA_NAME_IS_DEFAULT_DEF (simplified)
! 	      || ! prop_simulate_again_p (SSA_NAME_DEF_STMT (simplified)))
  	    {
! 	      ccp_prop_value_t *val = get_value (simplified);
! 	      if (val && val->lattice_val != VARYING)
! 		{
! 		  fold_undefer_overflow_warnings (true, stmt, 0);
! 		  return *val;
! 		}
  	    }
+ 	  else
+ 	    /* We may also not place a non-valueized copy in the lattice
+ 	       as that might become stale if we never re-visit this stmt.  */
+ 	    simplified = NULL_TREE;
  	}
        is_constant = simplified && is_gimple_min_invariant (simplified);
        fold_undefer_overflow_warnings (is_constant, stmt, 0);
Index: gcc/testsuite/gcc.dg/pr78644-1.c
===================================================================
*** gcc/testsuite/gcc.dg/pr78644-1.c	(nonexistent)
--- gcc/testsuite/gcc.dg/pr78644-1.c	(working copy)
***************
*** 0 ****
--- 1,21 ----
+ /* { dg-do compile { target int128 } } */
+ /* { dg-options "-Og -fipa-cp -w -Wno-psabi" } */
+ 
+ typedef unsigned __int128 u128;
+ typedef unsigned __int128 V __attribute__ ((vector_size (64)));
+ 
+ V x4;
+ 
+ static V
+ bar (u128 x2, u128 x3)
+ {
+   while (x4[0]--)
+     x2 /= x3 >>= 1;
+   return x2 + x3 + x4;
+ }
+ 
+ void
+ foo (void)
+ {
+   bar (0, 0);
+ }
Index: gcc/testsuite/gcc.dg/pr78644-2.c
===================================================================
*** gcc/testsuite/gcc.dg/pr78644-2.c	(nonexistent)
--- gcc/testsuite/gcc.dg/pr78644-2.c	(working copy)
***************
*** 0 ****
--- 1,20 ----
+ /* { dg-do compile { target int128 } } */
+ /* { dg-options "-Og -finline-functions-called-once -w -Wno-psabi" } */
+ 
+ typedef unsigned V __attribute__ ((vector_size (64)));
+ typedef unsigned __int128 U __attribute__ ((vector_size (64)));
+ 
+ U
+ bar4 (U u0, U u1)
+ {
+   if (u1[0])
+     u1 <<= 1;
+   return u0 + u1;
+ }
+ 
+ V
+ foo (U u, V v)
+ {
+   v |= (unsigned)bar4(u, (U){})[0];
+   return v;
+ }