2012-04-27  Paolo Bonzini  <bonzini@gnu.org>

	* tree-ssa-phiopt.c (conditional_replacement): Replace PHIs
	whose arguments are -1 and 0, by negating the result of the
	conditional.

testsuite:
2012-04-27  Paolo Bonzini  <bonzini@gnu.org>

	* gcc.c-torture/execute/20120427-2.c: New testcase.
	* gcc.dg/tree-ssa/phi-opt-10.c: New testcase.
	* gcc.dg/tree-ssa/ssa-pre-28.c: Bypass new optimization.
	* gcc.dg/tree-ssa/ssa-ifcombine-7.c: Look into ifcombine dump.

From-SVN: r186905