poly_int: DWARF locations

This patch adds support for DWARF location expressions
that involve polynomial offsets.  It adds a target hook that
says how the runtime invariants used in the offsets should be
represented in DWARF.  SVE vectors have to be a multiple of
128 bits in size, so the GCC port uses the number of 128-bit
blocks minus one as the runtime invariant.  However, in DWARF,
the vector length is exposed via a pseudo "VG" register that
holds the number of 64-bit elements in a vector.  Thus:

  indeterminate 1 == (VG / 2) - 1

The hook needs to be general enough to express this.
Note that in most cases the division and subtraction fold
away into surrounding expressions.

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

gcc/
	* target.def (dwarf_poly_indeterminate_value): New hook.
	* targhooks.h (default_dwarf_poly_indeterminate_value): Declare.
	* targhooks.c (default_dwarf_poly_indeterminate_value): New function.
	* doc/tm.texi.in (TARGET_DWARF_POLY_INDETERMINATE_VALUE): Document.
	* doc/tm.texi: Regenerate.
	* dwarf2out.h (build_cfa_loc, build_cfa_aligned_loc): Take the
	offset as a poly_int64.
	* dwarf2out.c (new_reg_loc_descr): Move later in file.  Take the
	offset as a poly_int64.
	(loc_descr_plus_const, loc_list_plus_const, build_cfa_aligned_loc):
	Take the offset as a poly_int64.
	(build_cfa_loc): Likewise.  Use loc_descr_plus_const.
	(frame_pointer_fb_offset): Change to a poly_int64.
	(int_loc_descriptor): Take the offset as a poly_int64.  Use
	targetm.dwarf_poly_indeterminate_value for polynomial offsets.
	(based_loc_descr): Take the offset as a poly_int64.
	Use strip_offset_and_add to handle (plus X (const)).
	Use new_reg_loc_descr instead of an open-coded version of the
	previous implementation.
	(mem_loc_descriptor): Handle CONST_POLY_INT.
	(compute_frame_pointer_to_fb_displacement): Take the offset as a
	poly_int64.  Use strip_offset_and_add to handle (plus X (const)).

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

From-SVN: r255868

gcc/ChangeLog

@@ -2,6 +2,33 @@
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
 
+	* target.def (dwarf_poly_indeterminate_value): New hook.
+	* targhooks.h (default_dwarf_poly_indeterminate_value): Declare.
+	* targhooks.c (default_dwarf_poly_indeterminate_value): New function.
+	* doc/tm.texi.in (TARGET_DWARF_POLY_INDETERMINATE_VALUE): Document.
+	* doc/tm.texi: Regenerate.
+	* dwarf2out.h (build_cfa_loc, build_cfa_aligned_loc): Take the
+	offset as a poly_int64.
+	* dwarf2out.c (new_reg_loc_descr): Move later in file.  Take the
+	offset as a poly_int64.
+	(loc_descr_plus_const, loc_list_plus_const, build_cfa_aligned_loc):
+	Take the offset as a poly_int64.
+	(build_cfa_loc): Likewise.  Use loc_descr_plus_const.
+	(frame_pointer_fb_offset): Change to a poly_int64.
+	(int_loc_descriptor): Take the offset as a poly_int64.  Use
+	targetm.dwarf_poly_indeterminate_value for polynomial offsets.
+	(based_loc_descr): Take the offset as a poly_int64.
+	Use strip_offset_and_add to handle (plus X (const)).
+	Use new_reg_loc_descr instead of an open-coded version of the
+	previous implementation.
+	(mem_loc_descriptor): Handle CONST_POLY_INT.
+	(compute_frame_pointer_to_fb_displacement): Take the offset as a
+	poly_int64.  Use strip_offset_and_add to handle (plus X (const)).
+
+2017-12-20  Richard Sandiford  <richard.sandiford@linaro.org>
+            Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
 	* rtl.h (reg_attrs::offset): Change from HOST_WIDE_INT to poly_int64.
 	(gen_rtx_REG_offset): Take the offset as a poly_int64.
 	* inchash.h (inchash::hash::add_poly_hwi): New function.

gcc/doc/tm.texi

@@ -3130,6 +3130,19 @@ the CFI label attached to the insn, @var{pattern} is the pattern of
 the insn and @var{index} is @code{UNSPEC_INDEX} or @code{UNSPECV_INDEX}.
 @end deftypefn
 
+@deftypefn {Target Hook} {unsigned int} TARGET_DWARF_POLY_INDETERMINATE_VALUE (unsigned int @var{i}, unsigned int *@var{factor}, int *@var{offset})
+Express the value of @code{poly_int} indeterminate @var{i} as a DWARF
+expression, with @var{i} counting from 1.  Return the number of a DWARF
+register @var{R} and set @samp{*@var{factor}} and @samp{*@var{offset}} such
+that the value of the indeterminate is:
+@smallexample
+value_of(@var{R}) / @var{factor} - @var{offset}
+@end smallexample
+
+A target only needs to define this hook if it sets
+@samp{NUM_POLY_INT_COEFFS} to a value greater than 1.
+@end deftypefn
+
 @defmac INCOMING_FRAME_SP_OFFSET
 A C expression whose value is an integer giving the offset, in bytes,
 from the value of the stack pointer register to the top of the stack

gcc/doc/tm.texi.in

@@ -2544,6 +2544,8 @@ terminate the stack backtrace.  New ports should avoid this.
 
 @hook TARGET_DWARF_HANDLE_FRAME_UNSPEC
 
+@hook TARGET_DWARF_POLY_INDETERMINATE_VALUE
+
 @defmac INCOMING_FRAME_SP_OFFSET
 A C expression whose value is an integer giving the offset, in bytes,
 from the value of the stack pointer register to the top of the stack

gcc/dwarf2out.h

@@ -267,9 +267,9 @@ struct GTY(()) dw_discr_list_node {
 
 /* Interface from dwarf2out.c to dwarf2cfi.c.  */
 extern struct dw_loc_descr_node *build_cfa_loc
-  (dw_cfa_location *, HOST_WIDE_INT);
+  (dw_cfa_location *, poly_int64);
 extern struct dw_loc_descr_node *build_cfa_aligned_loc
-  (dw_cfa_location *, HOST_WIDE_INT offset, HOST_WIDE_INT alignment);
+  (dw_cfa_location *, poly_int64, HOST_WIDE_INT);
 extern struct dw_loc_descr_node *mem_loc_descriptor
   (rtx, machine_mode mode, machine_mode mem_mode,
    enum var_init_status);

gcc/target.def

@@ -4136,6 +4136,21 @@ the CFI label attached to the insn, @var{pattern} is the pattern of\n\
 the insn and @var{index} is @code{UNSPEC_INDEX} or @code{UNSPECV_INDEX}.",
  void, (const char *label, rtx pattern, int index), NULL)
 
+DEFHOOK
+(dwarf_poly_indeterminate_value,
+ "Express the value of @code{poly_int} indeterminate @var{i} as a DWARF\n\
+expression, with @var{i} counting from 1.  Return the number of a DWARF\n\
+register @var{R} and set @samp{*@var{factor}} and @samp{*@var{offset}} such\n\
+that the value of the indeterminate is:\n\
+@smallexample\n\
+value_of(@var{R}) / @var{factor} - @var{offset}\n\
+@end smallexample\n\
+\n\
+A target only needs to define this hook if it sets\n\
+@samp{NUM_POLY_INT_COEFFS} to a value greater than 1.",
+ unsigned int, (unsigned int i, unsigned int *factor, int *offset),
+ default_dwarf_poly_indeterminate_value)
+
 /* ??? Documenting this hook requires a GFDL license grant.  */
 DEFHOOK_UNDOC
 (stdarg_optimize_hook,

gcc/targhooks.c

@@ -1874,6 +1874,15 @@ default_debug_unwind_info (void)
   return UI_NONE;
 }
 
+/* Targets that set NUM_POLY_INT_COEFFS to something greater than 1
+   must define this hook.  */
+
+unsigned int
+default_dwarf_poly_indeterminate_value (unsigned int, unsigned int *, int *)
+{
+  gcc_unreachable ();
+}
+
 /* Determine the correct mode for a Dwarf frame register that represents
    register REGNO.  */
 

gcc/targhooks.h

@@ -238,6 +238,9 @@ extern int default_label_align_max_skip (rtx_insn *);
 extern int default_jump_align_max_skip (rtx_insn *);
 extern section * default_function_section(tree decl, enum node_frequency freq,
 					  bool startup, bool exit);
+extern unsigned int default_dwarf_poly_indeterminate_value (unsigned int,
+							    unsigned int *,
+							    int *);
 extern machine_mode default_dwarf_frame_reg_mode (int);
 extern fixed_size_mode default_get_reg_raw_mode (int);
 extern bool default_keep_leaf_when_profiled ();