Restore RTL alias analysis for hard frame pointer

The change:

	2021-07-28  Bin Cheng  <bin.cheng@linux.alibaba.com>

	alias.c (init_alias_analysis): Don't skip prologue/epilogue.

broke the alias analysis for the hard frame pointer (when it is used as a
frame pointer, i.e. when the frame pointer is not eliminated) described in
the large comment at the top of the file, because static_reg_base_value is
set for it and, consequently, new_reg_base_value too.

When the instruction saving the stack pointer into the hard frame pointer in
the prologue is processed, it is viewed as a second set of the hard frame
pointer and to a different value by record_set, which then proceeds to reset
new_reg_base_value to 0 and the game is over.

gcc/
	* alias.cc (init_alias_analysis): Do not record sets to the hard
	frame pointer if the frame pointer has not been eliminated.