poly_int: rtx constants

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.

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

gcc/
	* doc/rtl.texi (const_poly_int): Document.  Also document the
	rtl sharing behavior.
	* 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.

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

From-SVN: r255862

1 files changed, 14 insertions, 0 deletions

diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi
index c28bdd5..888bbc9 100644
--- a/gcc/doc/rtl.texi
+++ b/gcc/doc/rtl.texi
@@ -1633,6 +1633,15 @@ is accessed with the macro @code{CONST_FIXED_VALUE}.  The high part of
 data is accessed with @code{CONST_FIXED_VALUE_HIGH}; the low part is
 accessed with @code{CONST_FIXED_VALUE_LOW}.
 
+@findex const_poly_int
+@item (const_poly_int:@var{m} [@var{c0} @var{c1} @dots{}])
+Represents a @code{poly_int}-style polynomial integer with coefficients
+@var{c0}, @var{c1}, @dots{}.  The coefficients are @code{wide_int}-based
+integers rather than rtxes.  @code{CONST_POLY_INT_COEFFS} gives the
+values of individual coefficients (which is mostly only useful in
+low-level routines) and @code{const_poly_int_value} gives the full
+@code{poly_int} value.
+
 @findex const_vector
 @item (const_vector:@var{m} [@var{x0} @var{x1} @dots{}])
 Represents a vector constant.  The square brackets stand for the vector
@@ -4236,6 +4245,11 @@ referring to it.
 @item
 All @code{const_int} expressions with equal values are shared.
 
+@cindex @code{const_poly_int}, RTL sharing
+@item
+All @code{const_poly_int} expressions with equal modes and values
+are shared.
+
 @cindex @code{pc}, RTL sharing
 @item
 There is only one @code{pc} expression.