Fix PR49471: canonicalize_loop_ivs should not generate unsigned types.

2011-07-27  Sebastian Pop  <sebastian.pop@amd.com>

	PR tree-optimization/49471
	* tree-ssa-loop-manip.c (canonicalize_loop_ivs): Build an unsigned
	iv only when the largest type is unsigned.  Do not call
	lang_hooks.types.type_for_size.

	* testsuite/libgomp.graphite/force-parallel-1.c: Un-xfail.
	* testsuite/libgomp.graphite/force-parallel-2.c: Adjust pattern.

From-SVN: r176838