Add a few testcases for fix missed optimization regressions

Add a few testcases for fix missed optimization regressions

Adds a few new testcases for some missed optimization regressions.
The analysis on how each should be optimized is in the testcases
themselves (and in the bug report).

Committed as obvious after running the testsuite to make sure they pass.

	PR tree-optimization/107823
	PR tree-optimization/110768
	PR tree-optimization/110941
	PR tree-optimization/110450
	PR tree-optimization/110841

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/ssa-thread-22.c: New test.
	* gcc.dg/tree-ssa/vrp-loop-1.c: New test.
	* gcc.dg/tree-ssa/vrp-loop-2.c: New test.
	* gcc.dg/tree-ssa/vrp-unreachable-1.c: New test.
	* gcc.dg/tree-ssa/vrp-unreachable-2.c: New test.

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