This patch changes the MEM_OFFSET and MEM_SIZE memory attributes
from HOST_WIDE_INT to poly_int64.  Most of it is mechanical,
but there is one nonbovious change in widen_memory_access.
Previously the main while loop broke with:

      /* Similarly for the decl.  */
      else if (DECL_P (attrs.expr)
               && DECL_SIZE_UNIT (attrs.expr)
               && TREE_CODE (DECL_SIZE_UNIT (attrs.expr)) == INTEGER_CST
               && compare_tree_int (DECL_SIZE_UNIT (attrs.expr), size) >= 0
               && (! attrs.offset_known_p || attrs.offset >= 0))
        break;

but it seemed wrong to optimistically assume the best case
when the offset isn't known (and thus might be negative).
As it happens, the "! attrs.offset_known_p" condition was
always false, because we'd already nullified attrs.expr in
that case:

  /* If we don't know what offset we were at within the expression, then
     we can't know if we've overstepped the bounds.  */
  if (! attrs.offset_known_p)
    attrs.expr = NULL_TREE;

The patch therefore drops "! attrs.offset_known_p ||" when
converting the offset check to the may/must interface.

2017-12-20  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* rtl.h (mem_attrs): Add a default constructor.  Change size and
	offset from HOST_WIDE_INT to poly_int64.
	* emit-rtl.h (set_mem_offset, set_mem_size, adjust_address_1)
	(adjust_automodify_address_1, set_mem_attributes_minus_bitpos)
	(widen_memory_access): Take the sizes and offsets as poly_int64s
	rather than HOST_WIDE_INTs.
	* alias.c (ao_ref_from_mem): Handle the new form of MEM_OFFSET.
	(offset_overlap_p): Take poly_int64s rather than HOST_WIDE_INTs
	and ints.
	(adjust_offset_for_component_ref): Change the offset from a
	HOST_WIDE_INT to a poly_int64.
	(nonoverlapping_memrefs_p): Track polynomial offsets and sizes.
	* cfgcleanup.c (merge_memattrs): Update after mem_attrs changes.
	* dce.c (find_call_stack_args): Likewise.
	* dse.c (record_store): Likewise.
	* dwarf2out.c (tls_mem_loc_descriptor, dw_sra_loc_expr): Likewise.
	* print-rtl.c (rtx_writer::print_rtx): Likewise.
	* read-rtl-function.c (test_loading_mem): Likewise.
	* rtlanal.c (may_trap_p_1): Likewise.
	* simplify-rtx.c (delegitimize_mem_from_attrs): Likewise.
	* var-tracking.c (int_mem_offset, track_expr_p): Likewise.
	* emit-rtl.c (mem_attrs_eq_p, get_mem_align_offset): Likewise.
	(mem_attrs::mem_attrs): New function.
	(set_mem_attributes_minus_bitpos): Change bitpos from a
	HOST_WIDE_INT to poly_int64.
	(set_mem_alias_set, set_mem_addr_space, set_mem_align, set_mem_expr)
	(clear_mem_offset, clear_mem_size, change_address)
	(get_spill_slot_decl, set_mem_attrs_for_spill): Directly
	initialize mem_attrs.
	(set_mem_offset, set_mem_size, adjust_address_1)
	(adjust_automodify_address_1, offset_address, widen_memory_access):
	Likewise.  Take poly_int64s rather than HOST_WIDE_INT.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r255875