tree-optimization/119103 - missed overwidening detection for shift

tree-optimization/119103 - missed overwidening detection for shift

When vectorizing a shift of u16 data by an amount that's known to
be less than 16 we currently fail to emit a vector u16 shift.  The
first reason is that the promotion of the shift amount is hoisted
only by PRE and that cannot preserve range info, the second reason
is that pattern detection doesn't use range info when computing
the precision required for an operation.

The following addresses the first issue by making LIM hoist all
expressions for the pass that runs right before PRE and the
second issue by querying ranges for the shift amount.

	PR tree-optimization/119103
	* tree-ssa-loop-im.cc (in_loop_pipeline): Globalize.
	(compute_invariantness): Override costing when we run
	right before PRE and PRE is enabled.
	(pass_lim::execute): Adjust.
	* tree-vect-patterns.cc (vect_determine_precisions_from_users):
	For variable shift amounts use range information.

	* gcc.target/i386/pr119103.c: New testcase.