[001/nnn] poly_int: add poly-int.h

[Richard Sandiford <richard.sandiford@linaro.org>]

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This patch adds a new "poly_int" class to represent polynomial integers
of the form:

  C0 + C1*X1 + C2*X2 ... + Cn*Xn

It also adds poly_int-based typedefs for offsets and sizes of various
precisions.  In these typedefs, the Ci coefficients are compile-time
constants and the Xi indeterminates are run-time invariants.  The number
of coefficients is controlled by the target and is initially 1 for all
ports.

Most routines can handle general coefficient counts, but for now a few
are specific to one or two coefficients.  Support for other coefficient
counts can be added when needed.

The patch also adds a new macro, IN_TARGET_CODE, that can be
set to indicate that a TU contains target-specific rather than
target-independent code.  When this macro is set and the number of
coefficients is 1, the poly-int.h classes define a conversion operator
to a constant.  This allows most existing target code to work without
modification.  The main exceptions are:

- values passed through ..., which need an explicit conversion to a
  constant

- ?: expression in which one arm ends up being a polynomial and the
  other remains a constant.  In these cases it would be valid to convert
  the constant to a polynomial and the polynomial to a constant, so a
  cast is needed to break the ambiguity.

The patch also adds a new target hook to return the estimated
value of a polynomial for costing purposes.

The patch also adds operator<< on wide_ints (it was already defined
for offset_int and widest_int).  I think this was originally excluded
because >> is ambiguous for wide_int, but << is useful for converting
bytes to bits, etc., so is worth defining on its own.  The patch also
adds operator% and operator/ for offset_int and widest_int, since those
types are always signed.  These changes allow the poly_int interface to
be more predictable.

I'd originally tried adding the tests as selftests, but that ended up
bloating cc1 by at least a third.  It also took a while to build them
at -O2.  The patch therefore uses plugin tests instead, where we can
force the tests to be built at -O0.  They still run in negligible time
when built that way.


2017-10-23  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* poly-int.h: New file.
	* poly-int-types.h: Likewise.
	* coretypes.h: Include them.
	(POLY_INT_CONVERSION): Define.
	* target.def (estimated_poly_value): New hook.
	* doc/tm.texi.in (TARGET_ESTIMATED_POLY_VALUE): New hook.
	* doc/tm.texi: Regenerate.
	* doc/poly-int.texi: New file.
	* doc/gccint.texi: Include it.
	* doc/rtl.texi: Describe restrictions on subreg modes.
	* Makefile.in (TEXI_GCCINT_FILES): Add poly-int.texi.
	* genmodes.c (NUM_POLY_INT_COEFFS): Provide a default definition.
	(emit_insn_modes_h): Emit a definition of NUM_POLY_INT_COEFFS.
	* targhooks.h (default_estimated_poly_value): Declare.
	* targhooks.c (default_estimated_poly_value): New function.
	* target.h (estimated_poly_value): Likewise.
	* wide-int.h (WI_UNARY_RESULT): Use wi::binary_traits.
	(wi::unary_traits): Delete.
	(wi::binary_traits::signed_shift_result_type): Define for
	offset_int << HOST_WIDE_INT, etc.
	(generic_wide_int::operator <<=): Define for all types and use
	wi::lshift instead of <<.
	(wi::hwi_with_prec): Add a default constructor.
	(wi::ints_for): New class.
	(operator <<): Define for all wide-int types.
	(operator /): New function.
	(operator %): Likewise.
	* selftest.h (ASSERT_MUST_EQ, ASSERT_MUST_EQ_AT, ASSERT_MAY_NE)
	(ASSERT_MAY_NE_AT): New macros.

gcc/testsuite/
	* gcc.dg/plugin/poly-int-tests.h,
	gcc.dg/plugin/poly-int-test-1.c,
	gcc.dg/plugin/poly-int-01_plugin.c,
	gcc.dg/plugin/poly-int-02_plugin.c,
	gcc.dg/plugin/poly-int-03_plugin.c,
	gcc.dg/plugin/poly-int-04_plugin.c,
	gcc.dg/plugin/poly-int-05_plugin.c,
	gcc.dg/plugin/poly-int-06_plugin.c,
	gcc.dg/plugin/poly-int-07_plugin.c: New tests.
	* gcc.dg/plugin/plugin.exp: Run them.


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