re PR tree-optimization/31136 (FRE ignores bit-field truncation (C and C++ front-end don't produce bit-field truncation)

2007-04-21  Richard Guenther  <rguenther@suse.de>

	PR middle-end/31136
	* fold-const.c (fold_unary): Call fold_convert_const on the
	original tree.

	* gcc.c-torture/execute/pr31136.c: New testcase.

From-SVN: r124020