[gcc(refs/users/meissner/heads/work146-vsize)] Add basic support for vector_size(32).

[Michael Meissner <meissner@gcc.gnu.org>]

https://gcc.gnu.org/g:6ea754404d5512bf2027aef55991fd86191100ab

commit 6ea754404d5512bf2027aef55991fd86191100ab
Author: Michael Meissner <meissner@linux.ibm.com>
Date:   Sun Nov 19 19:11:27 2023 -0500

    Add basic support for vector_size(32).
    
    We have had several users ask us to implement ways of using the Power10 load
    vector pair and store vector pair instructions to give their code a speed up
    due to reduced memory bandwidth.
    
    I had originally posted the following patches:
    
        *   https://gcc.gnu.org/pipermail/gcc-patches/2023-November/636077.html
        *   https://gcc.gnu.org/pipermail/gcc-patches/2023-November/636078.html
        *   https://gcc.gnu.org/pipermail/gcc-patches/2023-November/636083.html
        *   https://gcc.gnu.org/pipermail/gcc-patches/2023-November/636080.html
        *   https://gcc.gnu.org/pipermail/gcc-patches/2023-November/636081.html
    
    to add a set of built-in functions that use the PowePC __vector_pair type and
    that provide a set of functions to do basic operations on vector pair.
    
    After I posted these patches, it was decided that it would be better to have a
    new type that is used rather than a bunch of new built-in functions.  Within
    the GCC context, the best way to add this support is to extend the vector modes
    so that V4DFmode, V8SFmode, V4DImode, V8SImode, V16HImode, and V32QImode are
    used.
    
    While in theory you could add a whole new type that isn't a larger size vector,
    my experience with IEEE 128-bit floating point is that GCC really doesn't like
    2 modes that are the same size but have different implementations (such as we
    see with IEEE 128-bit floating point and IBM double-double 128-bit floating
    point).  So I did not consider adding a new mode for using with vector pairs.
    
    My original intention was to just implement V4DFmode and V8SFmode, since the
    primary users asking for vector pair support are people implementing the high
    end math libraries like Eigen and Blas.
    
    However in implementing this code, I discovered that we will need integer
    vector pair support as well as floating point vector pair.  The integer modes
    and types are needed to properly implement byte shuffling and vector
    comparisons which need integer vector pairs.
    
    With the current patches, vector pair support is not enabled by default.  The
    main reason is I have not implemented the support for byte shuffling which
    various tests depend on.
    
    I would also like to implement overloads for the vector built-in functions like
    vec_add, vec_sum, etc. that if you give it a vector pair, it would handle it
    just like if you give a vector type.
    
    In addition, once the various bugs are addressed, I would then implement the
    support so that automatic vectorization would consider using vector pairs
    instead of vectors.
    
    This is the first patch in the series.  It implements the basic modes, and
    it allows for initialization of the modes.  I've added some optimizations for
    extracting and setting fields within the vector pair.
    
    The second patch will implement the floating point vector pair support.
    
    The third patch will implement the integer vector pair support.
    
    The fourth patch will provide new tests to the test suite.
    
    When I test a sappy type loop (a[i] += (b[i] * c[i])), I generally see a 10%
    improvement over either auto-factorization, or just using the vector types.
    
    I have tested these patches on a little endian power10 system.  With
    -vector-size-32 disabled by default, there are no regressions in the
    test suite.
    
    I have also built and run the tests on both little endian power9 and big
    endian power9 systems, and there are no regressions.  Can I check these
    patches into the master branch?
    
    2023-11-19  Michael Meissner  <meissner@linux.ibm.com>
    
    GCC/
    
            * config/rs6000/constraint.md (eV): New constraint.
            * config/rs6000/predicates.md (cons_0_to_31_operand): New predicate.
            (easy_vector_constant): Add support for vector pair constants.
            (easy_vector_pair_constant): New predicate.
            (mam_assemble_input_operand): Allow other 16-byte vector modes than
            Immodest.
            * config/rs6000/rs6000-c.cc (rs6000_cpu_cpp_builtins): Define
            __VECTOR_SIZE_32__ if -mvector-size-32.
            * config/rs6000/rs6000-protos.h (vector_pair_to_vector_mode): New
            declaration.
            (split_vector_pair_constant): Likewise.
            (rs6000_expand_vector_pair_init): Likewise.
            * config/rs6000/rs6000.cc (rs6000_hard_regno_mode_ok_uncached): Use
            VECTOR_PAIR_MODE instead of comparing mode to OOmode.
            (rs6000_modes_tieable_p): Allow various vector pair modes to pair with
            each other.  Allow 16-byte vectors to pair with vector pair modes.
            (rs6000_setup_reg_addr_masks): Use VECTOR_PAIR_MODE instead of comparing
            mode to OOmode.
            (rs6000_init_hard_regno_mode_ok): Setup vector pair mode basic type
            information and reload handlers.
            (rs6000_option_override_internal): Warn if -mvector-pair-32 is used
            without -mcpu=power10 or -mmma.
            (vector_pair_to_vector_mode): New function.
            (split_vector_pair_constant): Likewise.
            (rs6000_expand_vector_pair_init): Likewise.
            (reg_offset_addressing_ok_p): Add support for vector pair modes.
            (rs6000_emit_move): Likewise.
            (rs6000_preferred_reload_class): Likewise.
            (altivec_expand_vec_perm_le): Likewise.
            (rs6000_opt_vars): Add -mvector-size-32 switch.
            (rs6000_split_multireg_move): Add support for vector pair modes.
            * config/rs6000/rs6000.h (VECTOR_PAIR_MODE): New macro.
            * config/rs6000/rs6000.md (wd mode attribute): Add vector pair modes.
            (RELOAD mode iterator): Likewise.
            (toplevel): Include vector-pair.md.
            * config/rs6000/rs6000.opt (-mvector-size-32): New option.
            * config/rs6000/vector-pair.md: New file.
            * doc/md.texi (PowerPC constraints): Document the eV constraint.

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