asf: Fix case of multiple stores with base offset [PR120660]

asf: Fix case of multiple stores with base offset [PR120660]

When having multiple stores with the same offset as the load, in the
case that we are eliminating the load, we were generating a mov instruction
for both of them, leading to the overwrite of the register containing the
loaded value.

This patch fixes this issue by generating a mov instruction only for the
first store in the store-load sequence that has the same offset as the load.
For the next ones that might be encountered, we use bit-field insertion.

Bootstrapped/regtested on AArch64 and x86_64.

	PR rtl-optimization/120660

gcc/ChangeLog:

	* avoid-store-forwarding.cc (process_store_forwarding):
	Fix instruction generation when haveing multiple stores with
	base offset.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr120660.c: New test.