On 10/23/2017 11:00 AM, Richard Sandiford wrote:
> This patch adds an rtl representation of poly_int values.
> There were three possible ways of doing this:
>
> (1) Add a new rtl code for the poly_ints themselves and store the
> coefficients as trailing wide_ints. This would give constants like:
>
> (const_poly_int [c0 c1 ... cn])
>
> The runtime value would be:
>
> c0 + c1 * x1 + ... + cn * xn
>
> (2) Like (1), but use rtxes for the coefficients. This would give
> constants like:
>
> (const_poly_int [(const_int c0)
> (const_int c1)
> ...
> (const_int cn)])
>
> although the coefficients could be const_wide_ints instead
> of const_ints where appropriate.
>
> (3) Add a new rtl code for the polynomial indeterminates,
> then use them in const wrappers. A constant like c0 + c1 * x1
> would then look like:
>
> (const:M (plus:M (mult:M (const_param:M x1)
> (const_int c1))
> (const_int c0)))
>
> There didn't seem to be that much to choose between them. The main
> advantage of (1) is that it's a more efficient representation and
> that we can refer to the cofficients directly as wide_int_storage.
Well, and #1 feels more like how we handle CONST_INT :-)
>
>
> 2017-10-23 Richard Sandiford <richard.sandif...@linaro.org>
> Alan Hayward <alan.hayw...@arm.com>
> David Sherwood <david.sherw...@arm.com>
>
> gcc/
> * doc/rtl.texi (const_poly_int): Document.
> * gengenrtl.c (excluded_rtx): Return true for CONST_POLY_INT.
> * rtl.h (const_poly_int_def): New struct.
> (rtx_def::u): Add a cpi field.
> (CASE_CONST_UNIQUE, CASE_CONST_ANY): Add CONST_POLY_INT.
> (CONST_POLY_INT_P, CONST_POLY_INT_COEFFS): New macros.
> (wi::rtx_to_poly_wide_ref): New typedef
> (const_poly_int_value, wi::to_poly_wide, rtx_to_poly_int64)
> (poly_int_rtx_p): New functions.
> (trunc_int_for_mode): Declare a poly_int64 version.
> (plus_constant): Take a poly_int64 instead of a HOST_WIDE_INT.
> (immed_wide_int_const): Take a poly_wide_int_ref rather than
> a wide_int_ref.
> (strip_offset): Declare.
> (strip_offset_and_add): New function.
> * rtl.def (CONST_POLY_INT): New rtx code.
> * rtl.c (rtx_size): Handle CONST_POLY_INT.
> (shared_const_p): Use poly_int_rtx_p.
> * emit-rtl.h (gen_int_mode): Take a poly_int64 instead of a
> HOST_WIDE_INT.
> (gen_int_shift_amount): Likewise.
> * emit-rtl.c (const_poly_int_hasher): New class.
> (const_poly_int_htab): New variable.
> (init_emit_once): Initialize it when NUM_POLY_INT_COEFFS > 1.
> (const_poly_int_hasher::hash): New function.
> (const_poly_int_hasher::equal): Likewise.
> (gen_int_mode): Take a poly_int64 instead of a HOST_WIDE_INT.
> (immed_wide_int_const): Rename to...
> (immed_wide_int_const_1): ...this and make static.
> (immed_wide_int_const): New function, taking a poly_wide_int_ref
> instead of a wide_int_ref.
> (gen_int_shift_amount): Take a poly_int64 instead of a HOST_WIDE_INT.
> (gen_lowpart_common): Handle CONST_POLY_INT.
> * cse.c (hash_rtx_cb, equiv_constant): Likewise.
> * cselib.c (cselib_hash_rtx): Likewise.
> * dwarf2out.c (const_ok_for_output_1): Likewise.
> * expr.c (convert_modes): Likewise.
> * print-rtl.c (rtx_writer::print_rtx, print_value): Likewise.
> * rtlhash.c (add_rtx): Likewise.
> * explow.c (trunc_int_for_mode): Add a poly_int64 version.
> (plus_constant): Take a poly_int64 instead of a HOST_WIDE_INT.
> Handle existing CONST_POLY_INT rtxes.
> * expmed.h (expand_shift): Take a poly_int64 instead of a
> HOST_WIDE_INT.
> * expmed.c (expand_shift): Likewise.
> * rtlanal.c (strip_offset): New function.
> (commutative_operand_precedence): Give CONST_POLY_INT the same
> precedence as CONST_DOUBLE and put CONST_WIDE_INT between that
> and CONST_INT.
> * rtl-tests.c (const_poly_int_tests): New struct.
> (rtl_tests_c_tests): Use it.
> * simplify-rtx.c (simplify_const_unary_operation): Handle
> CONST_POLY_INT.
> (simplify_const_binary_operation): Likewise.
> (simplify_binary_operation_1): Fold additions of symbolic constants
> and CONST_POLY_INTs.
> (simplify_subreg): Handle extensions and truncations of
> CONST_POLY_INTs.
> (simplify_const_poly_int_tests): New struct.
> (simplify_rtx_c_tests): Use it.
> * wide-int.h (storage_ref): Add default constructor.
> (wide_int_ref_storage): Likewise.
> (trailing_wide_ints): Use GTY((user)).
> (trailing_wide_ints::operator[]): Add a const version.
> (trailing_wide_ints::get_precision): New function.
> (trailing_wide_ints::extra_size): Likewise.
Do we need to define anything WRT structure sharing in rtl.texi for a
CONST_POLY_INT?
>
> Index: gcc/rtl.c
> ===================================================================
> --- gcc/rtl.c 2017-10-23 16:52:20.579835373 +0100
> +++ gcc/rtl.c 2017-10-23 17:00:54.443002147 +0100
> @@ -257,9 +261,10 @@ shared_const_p (const_rtx orig)
>
> /* CONST can be shared if it contains a SYMBOL_REF. If it contains
> a LABEL_REF, it isn't sharable. */
> + poly_int64 offset;
> return (GET_CODE (XEXP (orig, 0)) == PLUS
> && GET_CODE (XEXP (XEXP (orig, 0), 0)) == SYMBOL_REF
> - && CONST_INT_P (XEXP (XEXP (orig, 0), 1)));
> + && poly_int_rtx_p (XEXP (XEXP (orig, 0), 1), &offset));
Did this just change structure sharing for CONST_WIDE_INT?
> + /* Create a new rtx. There's a choice to be made here between installing
> + the actual mode of the rtx or leaving it as VOIDmode (for consistency
> + with CONST_INT). In practice the handling of the codes is different
> + enough that we get no benefit from using VOIDmode, and various places
> + assume that VOIDmode implies CONST_INT. Using the real mode seems like
> + the right long-term direction anyway. */
Certainly my preference is to get the mode in there. I see modeless
CONST_INTs as a long standing wart and I'm not keen to repeat it.
> Index: gcc/wide-int.h
> ===================================================================
> --- gcc/wide-int.h 2017-10-23 17:00:20.923835582 +0100
> +++ gcc/wide-int.h 2017-10-23 17:00:54.445999420 +0100
> @@ -613,6 +613,7 @@ #define SHIFT_FUNCTION \
> access. */
> struct storage_ref
> {
> + storage_ref () {}
> storage_ref (const HOST_WIDE_INT *, unsigned int, unsigned int);
>
> const HOST_WIDE_INT *val;
> @@ -944,6 +945,8 @@ struct wide_int_ref_storage : public wi:
> HOST_WIDE_INT scratch[2];
>
> public:
> + wide_int_ref_storage () {}
> +
> wide_int_ref_storage (const wi::storage_ref &);
>
> template <typename T>
So doesn't this play into the whole question about initialization of
these objects. So I'll defer on this hunk until we settle that
question, but the rest is OK.
Jeff
