[PATCH] Fix PR68026

[Richard Biener <rguenther@suse.de>]

This fixes a missed optimization in CCP bit-propagation where we
lost the fact of upper zero bits of unsigned VARYING values
(the wide-int conversion made somewhat of a mess of all this).

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

Richard.

2015-10-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/68026
	* tree-ssa-ccp.c (get_value_for_expr): Zero-extend mask for
	unsigned VARYING values.

	* gcc.dg/tree-ssa/ssa-ccp-39.c: New testcase.

Index: gcc/tree-ssa-ccp.c
===================================================================
*** gcc/tree-ssa-ccp.c	(revision 229031)
--- gcc/tree-ssa-ccp.c	(working copy)
*************** get_value_for_expr (tree expr, bool for_
*** 629,634 ****
--- 629,639 ----
        val.mask = -1;
        val.value = NULL_TREE;
      }
+ 
+   if (val.lattice_val == VARYING
+       && TYPE_UNSIGNED (TREE_TYPE (expr)))
+     val.mask = wi::zext (val.mask, TYPE_PRECISION (TREE_TYPE (expr)));
+ 
    return val;
  }
  
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-39.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-39.c	(revision 0)
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-39.c	(working copy)
***************
*** 0 ****
--- 1,19 ----
+ /* { dg-do run } */
+ /* { dg-options "-O -fdump-tree-ccp1" } */
+ 
+ int main (void)
+ {
+   volatile int x1 = 1;
+   volatile int x2 = 1;
+   int x3 = 2;
+   int t = 1;
+ 
+   t = 3<=(x2|1|x3|x1-1U);
+ 
+   if (t == 1) {} 
+   else { __builtin_abort(); }
+ 
+   return 0;
+ }
+ 
+ /* { dg-final { scan-tree-dump-not "abort" "ccp1" } } */