phiopt: Use rewrite_to_defined_overflow in move_stmt [PR116938]

phiopt: Use rewrite_to_defined_overflow in move_stmt [PR116938]

As mentioned previously the rewrite in move_stmt should be
using gimple_needing_rewrite_undefined/rewrite_to_defined_unconditional
instead of just rewriting the VCE.
This moves move_stmt over to those APIs.

A few testcases needed to be updated due to ABS_EXPR rewrite that happens.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/116938

gcc/ChangeLog:

	* tree-ssa-phiopt.cc (move_stmt): Use rewrite_to_defined_overflow
	isntead of manually doing the rewrite of the VCE.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi-opt-40.c: Update to expect ABSU_EXPR.
	* gcc.dg/tree-ssa/phi-opt-41.c: Likewise.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>