This patch makes the DWARF code use poly_int64 rather than
HOST_WIDE_INT for CFA offsets.  The main changes are:

- to make reg_save use a DW_CFA_expression representation when
  the offset isn't constant and

- to record the CFA information alongside a def_cfa_expression
  if either offset is polynomial, since it's quite difficult
  to reconstruct the CFA information otherwise.

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

gcc/
	* gengtype.c (main): Handle poly_int64_pod.
	* dwarf2out.h (dw_cfi_oprnd_cfa_loc): New dw_cfi_oprnd_type.
	(dw_cfi_oprnd::dw_cfi_cfa_loc): New field.
	(dw_cfa_location::offset, dw_cfa_location::base_offset): Change
	from HOST_WIDE_INT to poly_int64_pod.
	* dwarf2cfi.c (queued_reg_save::cfa_offset): Likewise.
	(copy_cfa): New function.
	(lookup_cfa_1): Use the cached dw_cfi_cfa_loc, if it exists.
	(cfi_oprnd_equal_p): Handle dw_cfi_oprnd_cfa_loc.
	(cfa_equal_p, dwarf2out_frame_debug_adjust_cfa)
	(dwarf2out_frame_debug_cfa_offset, dwarf2out_frame_debug_expr)
	(initial_return_save): Treat offsets as poly_ints.
	(def_cfa_0): Likewise.  Cache the CFA in dw_cfi_cfa_loc if either
	offset is nonconstant.
	(reg_save): Take the offset as a poly_int64.  Fall back to
	DW_CFA_expression for nonconstant offsets.
	(queue_reg_save): Take the offset as a poly_int64.
	* dwarf2out.c (dw_cfi_oprnd2_desc): Handle DW_CFA_def_cfa_expression.

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

From-SVN: r255884