re PR tree-optimization/21137 (Convert (a >> 2) & 1 != 0 into a & 4 != 0)

re PR tree-optimization/21137 (Convert (a >> 2) & 1 != 0 into a & 4 != 0)

2006-02-26  Roger Sayle  <roger@eyesopen.com>
	    James A. Morrison  <phython@gcc.gnu.org>

	PR middle-end/21137
	* fold-const.c (fold_binary) <EQ_EXPR>:  Fold ((X>>C1)&C2) eq/ne 0,
	when C2 is a power of two, as either (X&(C2<<C1)) eq/ne 0 if the
	new constant C2<<C1, or as (X<0) or (X,false) depending upon the
	signedness of the shift operation.

	* gcc.dg/fold-eqandshift-1.c: New test case.

Co-Authored-By: James A. Morrison <phython@gcc.gnu.org>
From-SVN: r111453