ifcvt.c (noce_try_sign_mask): New function to transform "x = (y < 0) ? z ...

	* ifcvt.c (noce_try_sign_mask): New function to transform
	"x = (y < 0) ? z : 0" into the equivalent "x = (y >> C) & z".
	(noce_process_if_block): Call noce_try_sign_mask.

	* gcc.c-torture/execute/20040309-1.c: New test case.

Co-Authored-By: Andrew Pinski <pinskia@physics.uc.edu>

From-SVN: r79205