common.opt: Add description of the new -fgcse-las flag.

common.opt: Add description of the new -fgcse-las flag.

2003-10-17  Mostafa Hagog  <mustafa@il.ibm.com>

	* common.opt: Add description of the new -fgcse-las flag.
	* flags.h (flag_gcse_las): Declaration of global flag_gcse_las.
	* gcse.c (hash_scan_set): Handle the case of store expression and
	insert the memory expression to the hash table, this way we make it
	possible to discover redundant loads after stores and remove them.
	(pre_insert_copy_insn): moved the call to update_ld_motion_stores,
	to pre_insert_copies, it is not the correct place to call it after
	adding stores to be in the available expression hash table.
	(pre_insert_copies): Added the call to update_ld_motion_stores when
	one or more copies were inserted.
	* opts.c (common_handle_option): Handle the -fgcse-las flag.
	* toplev.c (flag_gcse_las): Initialization of flag_gcse_las.

	* doc/invoke.tex: Document new -fgcse-las flag.

From-SVN: r72612