avoid-store-forwarding: bail when an instruction may throw [PR117816]

avoid-store-forwarding: bail when an instruction may throw [PR117816]

Avoid-store-forwarding doesn't handle the case where an instruction in
the store-load sequence contains a REG_EH_REGION note, leading to the
insertion of instructions after it, while it should be the last
instruction in the basic block. This causes an ICE when compiling
using `-O -fnon-call-exceptions -favoid-store-forwarding
-fno-forward-propagate -finstrument-functions`.

This patch rejects the transformation when there are instructions in
the sequence that may throw an exeption.

	PR rtl-optimization/117816

gcc/ChangeLog:

	* avoid-store-forwarding.cc (store_forwarding_analyzer::avoid_store_forwarding):
	Reject the transformation when having instructions that may
	throw exceptions in the sequence.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr117816.c: New test.