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#
# Copyright (C) 2020 Collabora, Ltd.
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice (including the next
# paragraph) shall be included in all copies or substantial portions of the
# Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
import sys
import itertools
from isa_parse import parse_instructions, opname_to_c, expand_states
from mako.template import Template
instructions = parse_instructions(sys.argv[1])
# Constructs a reserved mask for a derived to cull impossible encodings
def reserved_mask(derived):
((pos, width), opts) = derived
reserved = [x is None for x in opts]
mask = sum([(y << x) for x, y in enumerate(reserved)])
return (pos, width, mask)
def reserved_masks(op):
masks = [reserved_mask(m) for m in op[2].get("derived", [])]
return [m for m in masks if m[2] != 0]
# To decode instructions, pattern match based on the rules:
#
# 1. Execution unit (FMA or ADD) must line up.
# 2. All exact bits must match.
# 3. No fields should be reserved in a legal encoding.
# 4. Tiebreaker: Longer exact masks (greater unsigned bitwise inverses) win.
#
# To implement, filter the execution unit and check for exact bits in
# descending order of exact mask length. Check for reserved fields per
# candidate and succeed if it matches.
# found.
def decode_op(instructions, is_fma):
# Filter out the desired execution unit
options = [n for n in instructions.keys() if (n[0] == '*') == is_fma]
# Sort by exact masks, descending
MAX_MASK = (1 << (23 if is_fma else 20)) - 1
options.sort(key = lambda n: (MAX_MASK ^ instructions[n][2]["exact"][0]))
# Map to what we need to template
mapped = [(opname_to_c(op), instructions[op][2]["exact"], reserved_masks(instructions[op])) for op in options]
# Generate checks in order
template = """void
bi_disasm_${unit}(FILE *fp, unsigned bits, struct bifrost_regs *srcs, struct bifrost_regs *next_regs, unsigned staging_register, unsigned branch_offset, struct bi_constants *consts)
{
% for (i, (name, (emask, ebits), derived)) in enumerate(options):
% if len(derived) > 0:
${"else " if i > 0 else ""}if (unlikely(((bits & ${hex(emask)}) == ${hex(ebits)})
% for (pos, width, reserved) in derived:
&& !(${hex(reserved)} & (1 << _BITS(bits, ${pos}, ${width})))
% endfor
))
% else:
${"else " if i > 0 else ""}if (unlikely(((bits & ${hex(emask)}) == ${hex(ebits)})))
% endif
bi_disasm_${name}(fp, bits, srcs, next_regs, staging_register, branch_offset, consts);
% endfor
else
fprintf(fp, "INSTR_INVALID_ENC ${unit} %X\\n", bits);
}"""
return Template(template).render(options = mapped, unit = "fma" if is_fma else "add")
# Decoding emits a series of function calls to e.g. `fma_fadd_v2f16`. We need to
# emit functions to disassemble a single decoded instruction in a particular
# state. Sync prototypes to avoid moves when calling.
disasm_op_template = Template("""static void
bi_disasm_${c_name}(FILE *fp, unsigned bits, struct bifrost_regs *srcs, struct bifrost_regs *next_regs, unsigned staging_register, unsigned branch_offset, struct bi_constants *consts)
{
${body.strip()}
}
""")
lut_template_only = Template(""" static const char *${field}[] = {
${", ".join(['"' + x + '"' for x in table])}
};
""")
# Given a lookup table written logically, generate an accessor
lut_template = Template(""" static const char *${field}_table[] = {
${", ".join(['"' + x + '"' for x in table])}
};
const char *${field} = ${field}_table[_BITS(bits, ${pos}, ${width})];
""")
# Helpers for decoding follow. pretty_mods applies dot syntax
def pretty_mods(opts, default):
return [('.' + (opt or 'reserved') if opt != default else '') for opt in opts]
# Recursively searches for the set of free variables required by an expression
def find_context_keys_expr(expr):
if isinstance(expr, list):
return set.union(*[find_context_keys_expr(x) for x in expr[1:]])
elif expr[0] == '#':
return set()
else:
return set([expr])
def find_context_keys(desc, test):
keys = set()
if len(test) > 0:
keys |= find_context_keys_expr(test)
for i, (_, vals) in enumerate(desc.get('derived', [])):
for j, val in enumerate(vals):
if val is not None:
keys |= find_context_keys_expr(val)
return keys
# Compiles a logic expression to Python expression, ctx -> { T, F }
EVALUATORS = {
'and': ' and ',
'or': ' or ',
'eq': ' == ',
'neq': ' != ',
}
def compile_derived_inner(expr, keys):
if expr == []:
return 'True'
elif expr is None or expr[0] == 'alias':
return 'False'
elif isinstance(expr, list):
args = [compile_derived_inner(arg, keys) for arg in expr[1:]]
return '(' + EVALUATORS[expr[0]].join(args) + ')'
elif expr[0] == '#':
return "'{}'".format(expr[1:])
elif expr == 'ordering':
return expr
else:
return "ctx[{}]".format(keys.index(expr))
def compile_derived(expr, keys):
return eval('lambda ctx, ordering: ' + compile_derived_inner(expr, keys))
# Generate all possible combinations of values and evaluate the derived values
# by bruteforce evaluation to generate a forward mapping (values -> deriveds)
def evaluate_forward_derived(vals, ctx, ordering):
for j, expr in enumerate(vals):
if expr(ctx, ordering):
return j
return None
def evaluate_forward(keys, derivf, testf, ctx, ordering):
if not testf(ctx, ordering):
return None
deriv = []
for vals in derivf:
evaled = evaluate_forward_derived(vals, ctx, ordering)
if evaled is None:
return None
deriv.append(evaled)
return deriv
def evaluate_forwards(keys, derivf, testf, mod_vals, ordered):
orderings = ["lt", "gt"] if ordered else [None]
return [[evaluate_forward(keys, derivf, testf, i, order) for i in itertools.product(*mod_vals)] for order in orderings]
# Invert the forward mapping (values -> deriveds) of finite sets to produce a
# backwards mapping (deriveds -> values), suitable for disassembly. This is
# possible since the encoding is unambiguous, so this mapping is a bijection
# (after reserved/impossible encodings)
def invert_lut(value_size, forward, derived, mod_map, keys, mod_vals):
backwards = [None] * (1 << value_size)
for (i, deriveds), ctx in zip(enumerate(forward), itertools.product(*mod_vals)):
# Skip reserved
if deriveds == None:
continue
shift = 0
param = 0
for j, ((x, width), y) in enumerate(derived):
param += (deriveds[j] << shift)
shift += width
assert(param not in backwards)
backwards[param] = ctx
return backwards
# Compute the value of all indirectly specified modifiers by using the
# backwards mapping (deriveds -> values) as a run-time lookup table.
def build_lut(mnemonic, desc, test):
# Construct the system
facts = []
mod_map = {}
for ((name, pos, width), default, values) in desc.get('modifiers', []):
mod_map[name] = (width, values, pos, default)
derived = desc.get('derived', [])
# Find the keys and impose an order
key_set = find_context_keys(desc, test)
ordered = 'ordering' in key_set
key_set.discard('ordering')
keys = list(key_set)
# Evaluate the deriveds for every possible state, forming a (state -> deriveds) map
testf = compile_derived(test, keys)
derivf = [[compile_derived(expr, keys) for expr in v] for (_, v) in derived]
mod_vals = [mod_map[k][1] for k in keys]
forward = evaluate_forwards(keys, derivf, testf, mod_vals, ordered)
# Now invert that map to get a (deriveds -> state) map
value_size = sum([width for ((x, width), y) in derived])
backwards = [invert_lut(value_size, f, derived, mod_map, keys, mod_vals) for f in forward]
# From that map, we can generate LUTs
output = ""
if ordered:
output += "bool ordering = (_BITS(bits, {}, 3) > _BITS(bits, {}, 3));\n".format(desc["srcs"][0][0], desc["srcs"][1][0])
for j, key in enumerate(keys):
# Only generate tables for indirect specifiers
if mod_map[key][2] is not None:
continue
idx_parts = []
shift = 0
for ((pos, width), _) in derived:
idx_parts.append("(_BITS(bits, {}, {}) << {})".format(pos, width, shift))
shift += width
built_idx = (" | ".join(idx_parts)) if len(idx_parts) > 0 else "0"
default = mod_map[key][3]
if ordered:
for i, order in enumerate(backwards):
options = [ctx[j] if ctx is not None and ctx[j] is not None else "reserved" for ctx in order]
output += lut_template_only.render(field = key + "_" + str(i), table = pretty_mods(options, default))
output += " const char *{} = ordering ? {}_1[{}] : {}_0[{}];\n".format(key, key, built_idx, key, built_idx)
else:
options = [ctx[j] if ctx is not None and ctx[j] is not None else "reserved" for ctx in backwards[0]]
output += lut_template_only.render(field = key + "_table", table = pretty_mods(options, default))
output += " const char *{} = {}_table[{}];\n".format(key, key, built_idx)
return output
def disasm_mod(mod, skip_mods):
if mod[0][0] in skip_mods:
return ''
else:
return ' fputs({}, fp);\n'.format(mod[0][0])
def disasm_op(name, op):
(mnemonic, test, desc) = op
is_fma = mnemonic[0] == '*'
# Modifiers may be either direct (pos is not None) or indirect (pos is
# None). If direct, we just do the bit lookup. If indirect, we use a LUT.
body = ""
skip_mods = []
body += build_lut(mnemonic, desc, test)
for ((mod, pos, width), default, opts) in desc.get('modifiers', []):
if pos is not None:
body += lut_template.render(field = mod, table = pretty_mods(opts, default), pos = pos, width = width) + "\n"
# Mnemonic, followed by modifiers
body += ' fputs("{}", fp);\n'.format(mnemonic)
srcs = desc.get('srcs', [])
for mod in desc.get('modifiers', []):
# Skip per-source until next block
if mod[0][0][-1] in "0123" and int(mod[0][0][-1]) < len(srcs):
continue
body += disasm_mod(mod, skip_mods)
body += ' fputs(" ", fp);\n'
body += ' bi_disasm_dest_{}(fp, next_regs);\n'.format('fma' if is_fma else 'add')
# Next up, each source. Source modifiers are inserterd here
for i, (pos, mask) in enumerate(srcs):
body += ' fputs(", ", fp);\n'
body += ' dump_src(fp, _BITS(bits, {}, 3), *srcs, consts, {});\n'.format(pos, "true" if is_fma else "false")
# Error check if needed
if (mask != 0xFF):
body += ' if (!({} & (1 << _BITS(bits, {}, 3)))) fputs("(INVALID)", fp);\n'.format(hex(mask), pos, 3)
# Print modifiers suffixed with this src number (e.g. abs0 for src0)
for mod in desc.get('modifiers', []):
if mod[0][0][-1] == str(i):
body += disasm_mod(mod, skip_mods)
# And each immediate
for (imm, pos, width) in desc.get('immediates', []):
body += ' fprintf(fp, ", {}:%u", _BITS(bits, {}, {}));\n'.format(imm, pos, width)
# Attach a staging register if one is used
if desc.get('staging'):
body += ' fprintf(fp, ", @r%u", staging_register);\n'
body += ' fputs("\\n", fp);\n'
return disasm_op_template.render(c_name = opname_to_c(name), body = body)
print('#include "util/macros.h"')
print('#include "disassemble.h"')
states = expand_states(instructions)
print('#define _BITS(bits, pos, width) (((bits) >> (pos)) & ((1 << (width)) - 1))')
for st in states:
print(disasm_op(st, states[st]))
print(decode_op(states, True))
print(decode_op(states, False))