midgard_nir_algebraic.py

#
# Copyright (C) 2018 Alyssa Rosenzweig
# Copyright (C) 2019-2020 Collabora, Ltd.
#
# Copyright (C) 2016 Intel Corporation
#
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# Software is furnished to do so, subject to the following conditions:
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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import argparse
import sys
import math

a = 'a'
b = 'b'
c = 'c'

algebraic = [
   # Allows us to schedule as a multiply by 2
   (('~fadd', ('fadd', a, b), a), ('fadd', ('fadd', a, a), b)),
]

algebraic_late = [
    # ineg must be lowered late, but only for integers; floats will try to
    # have modifiers attached... hence why this has to be here rather than
    # a more standard lower_negate approach

    (('ineg', a), ('isub', 0, a)),

    # Likewise we want fsub lowered but not isub
    (('fsub', a, b), ('fadd', a, ('fneg', b))),

    # These two special-cases save space/an op than the actual csel op +
    # scheduler flexibility

    (('b32csel', a, 'b@32', 0), ('iand', a, b)),
    (('b32csel', a, 0, 'b@32'), ('iand', ('inot', a), b)),

    # Fuse sat_signed. This should probably be shared with Bifrost
    (('~fmin', ('fmax', a, -1.0), 1.0), ('fsat_signed_mali', a)),
    (('~fmax', ('fmin', a, 1.0), -1.0), ('fsat_signed_mali', a)),

    # Fuse clamp_positive. This should probably be shared with Utgard/bifrost
    (('fmax', a, 0.0), ('fclamp_pos_mali', a)),

    (('ishl', 'a@16', b), ('u2u16', ('ishl', ('u2u32', a), b))),
    (('ishr', 'a@16', b), ('i2i16', ('ishr', ('i2i32', a), b))),
    (('ushr', 'a@16', b), ('u2u16', ('ushr', ('u2u32', a), b))),

    (('ishl', 'a@8', b), ('u2u8', ('u2u16', ('ishl', ('u2u32', ('u2u16', a)), b)))),
    (('ishr', 'a@8', b), ('i2i8', ('i2i16', ('ishr', ('i2i32', ('i2i16', a)), b)))),
    (('ushr', 'a@8', b), ('u2u8', ('u2u16', ('ushr', ('u2u32', ('u2u16', a)), b)))),

    # Canonical form. The scheduler will convert back if it makes sense.
    (('fmul', a, 2.0), ('fadd', a, a))
]

# Size conversion is redundant to Midgard but needed for NIR, and writing this
# lowering in MIR would be painful without a competent builder, so eat the
# extra instruction
for sz in ('8', '16', '32'):
    converted = ('u2u32', a) if sz != '32' else a
    algebraic_late += [(('ufind_msb', 'a@' + sz), ('isub', 31, ('uclz', converted)))]

# Midgard is able to type convert down by only one "step" per instruction; if
# NIR wants more than one step, we need to break up into multiple instructions.
# Nevertheless, we can do both a size step and a floating/int step at once.

converts = []

for op in ('u2u', 'i2i', 'f2f', 'i2f', 'u2f', 'f2i', 'f2u'):
    srcsz_max = 64
    dstsz_max = 64
    # 8 bit float doesn't exist
    srcsz_min = 8 if op[0] != 'f' else 16
    dstsz_min = 8 if op[2] != 'f' else 16
    dstsz = dstsz_min
    # Iterate over all possible destination and source sizes
    while dstsz <= dstsz_max:
        srcsz = srcsz_min
        while srcsz <= srcsz_max:
            # Size converter lowering is only needed if src and dst sizes are
            # spaced by a factor > 2.
            if srcsz != dstsz and (srcsz * 2 != dstsz and srcsz != dstsz * 2):
                cursz = srcsz
                rule = a
                # When converting down we first do the type conversion followed
                # by one or more size conversions. When converting up, we do
                # the type conversion at the end. This way we don't have to
                # deal with the fact that f2f8 doesn't exists.
                sizeconvop = op[0] + '2' + op[0] if srcsz < dstsz else op[2] + '2' + op[2]
                if srcsz > dstsz and op[0] != op[2]:
                    rule = (op + str(int(cursz)), rule)
                while cursz != dstsz:
                    cursz = cursz / 2 if dstsz < srcsz else cursz * 2
                    rule = (sizeconvop + str(int(cursz)), rule)
                if srcsz < dstsz and op[0] != op[2]:
                    rule = (op + str(int(cursz)), rule)
                converts += [((op + str(int(dstsz)), 'a@' + str(int(srcsz))), rule)]
            srcsz *= 2
        dstsz *= 2

# Try to force constants to the right
constant_switch = [
        # fge gets flipped to fle, so we invert to keep the order
        (('fge', 'a', '#b'), (('inot', ('flt', a, b)))),
        (('fge32', 'a', '#b'), (('inot', ('flt32', a, b)))),
        (('ige32', 'a', '#b'), (('inot', ('ilt32', a, b)))),
        (('uge32', 'a', '#b'), (('inot', ('ult32', a, b)))),

        # fge gets mapped to fle with a flip
        (('flt32', '#a', 'b'), ('inot', ('fge32', a, b))),
        (('ilt32', '#a', 'b'), ('inot', ('ige32', a, b))),
        (('ult32', '#a', 'b'), ('inot', ('uge32', a, b)))
]

# ..since the above switching happens after algebraic stuff is done
cancel_inot = [
        (('inot', ('inot', a)), a)
]

# Midgard scales fsin/fcos arguments by pi.
# Pass must be run only once, after the main loop

scale_trig = [
        (('fsin', a), ('fsin', ('fdiv', a, math.pi))),
        (('fcos', a), ('fcos', ('fdiv', a, math.pi))),
]

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('-p', '--import-path', required=True)
    args = parser.parse_args()
    sys.path.insert(0, args.import_path)
    run()


def run():
    import nir_algebraic  # pylint: disable=import-error

    print('#include "midgard_nir.h"')

    print(nir_algebraic.AlgebraicPass("midgard_nir_lower_algebraic_early",
                                      algebraic).render())

    print(nir_algebraic.AlgebraicPass("midgard_nir_lower_algebraic_late",
                                      algebraic_late + converts + constant_switch).render())

    print(nir_algebraic.AlgebraicPass("midgard_nir_scale_trig",
                                      scale_trig).render())

    print(nir_algebraic.AlgebraicPass("midgard_nir_cancel_inot",
                                      cancel_inot).render())


if __name__ == '__main__':
    main()