auto-inc-dec: Set alignment properly

When auto-inc-dec creates a new mem to compute the cost of doing some
transform, it forgets to copy over the alignment of the original mem.
This gives wrong costs, for example, for rs6000 a floating point load
or store is hugely expensive if unaligned.  This patch fixes it.


	* auto-inc-dec.c (attempt_change): Set the alignment of the
	temporary memory to that of the original.

From-SVN: r270419

gcc/ChangeLog

-2019-04-10  Joao Moreira  <jmoreira@suse.de>
+2019-04-17  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	* auto-inc-dec.c (attempt_change): Set the alignment of the
+	temporary memory to that of the original.
+
+2019-04-17  Joao Moreira  <jmoreira@suse.de>
 
 	* targhooks.c (default_print_patchable_function_entry): Emit
 	__patchable_function_entries section with writable flags to allow

gcc/auto-inc-dec.c

@@ -471,6 +471,7 @@ attempt_change (rtx new_addr, rtx inc_reg)
   int regno;
   rtx mem = *mem_insn.mem_loc;
   machine_mode mode = GET_MODE (mem);
+  int align = MEM_ALIGN (mem);
   rtx new_mem;
   int old_cost = 0;
   int new_cost = 0;
@@ -478,6 +479,7 @@ attempt_change (rtx new_addr, rtx inc_reg)
 
   PUT_MODE (mem_tmp, mode);
   XEXP (mem_tmp, 0) = new_addr;
+  set_mem_align (mem_tmp, align);
 
   old_cost = (set_src_cost (mem, mode, speed)
 	      + set_rtx_cost (PATTERN (inc_insn.insn), speed));