[tree-ssa] Fix typo -- GMP failure

[law@redhat.com]

Sigh.   A simple typo (GT_EXPR when I meant LT_EXPR) was causing us to
incorrectly transform an ABS_EXPR expression.   This only happened
in rare cases because the typo was in the code to initialize COND_EXPR
for the first time.  Subsequent uses all DTRT.  Sigh.

Anyway the GMP testsuite tripped on this one.  I've extracted a nice simple
testcase for our testsuite. 

Bootstrapped and regression tested i686-pc-linux-gnu.

	* tree-ssa-dom.c (simplify_rhs_and_lookup_avail_expr): Fix typo.
	Eliminate unnecessary test of VAL.

	* gcc.c-torture/execute/20040319-1.c: New test.

Index: tree-ssa-dom.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Attic/tree-ssa-dom.c,v
retrieving revision 1.1.2.148
diff -c -p -r1.1.2.148 tree-ssa-dom.c
*** tree-ssa-dom.c	16 Mar 2004 22:31:55 -0000	1.1.2.148
--- tree-ssa-dom.c	19 Mar 2004 21:16:01 -0000
*************** simplify_rhs_and_lookup_avail_expr (stru
*** 1794,1800 ****
  
  	  if (! dummy_cond)
  	    {
! 	      dummy_cond = build (GT_EXPR, boolean_type_node,
  				  op, integer_zero_node);
  	      dummy_cond = build (COND_EXPR, void_type_node,
  				  dummy_cond, NULL, NULL);
--- 1794,1800 ----
  
  	  if (! dummy_cond)
  	    {
! 	      dummy_cond = build (LT_EXPR, boolean_type_node,
  				  op, integer_zero_node);
  	      dummy_cond = build (COND_EXPR, void_type_node,
  				  dummy_cond, NULL, NULL);
*************** simplify_rhs_and_lookup_avail_expr (stru
*** 1817,1823 ****
  	{
  	  tree t;
  
! 	  if (val && integer_onep (val))
  	    t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
  	  else
  	    t = op;
--- 1817,1823 ----
  	{
  	  tree t;
  
! 	  if (integer_onep (val))
  	    t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
  	  else
  	    t = op;
Index: testsuite/gcc.c-torture/execute/20040319-1.c
===================================================================
RCS file: testsuite/gcc.c-torture/execute/20040319-1.c
diff -N testsuite/gcc.c-torture/execute/20040319-1.c
*** /dev/null	1 Jan 1970 00:00:00 -0000
--- testsuite/gcc.c-torture/execute/20040319-1.c	19 Mar 2004 21:16:56 -0000
***************
*** 0 ****
--- 1,17 ----
+ int
+ blah (int zzz)
+ {
+   int foo;
+   if (zzz >= 0)
+     return 1;
+   foo = (zzz >= 0 ? (zzz) : -(zzz));
+   return foo;
+ }
+ 
+ main()
+ {
+   if (blah (-1) != 1)
+     abort ();
+   else
+     exit (0);
+ }