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| 1 #!/usr/bin/python |
| 2 # |
| 3 # Copyright 2009 The Native Client Authors. All rights reserved. |
| 4 # Use of this source code is governed by a BSD-style license that can |
| 5 # be found in the LICENSE file. |
| 6 # Copyright 2009, Google Inc. |
| 7 # |
| 8 |
| 9 """ |
| 10 Responsible for generating the decoder based on parsed table representations. |
| 11 """ |
| 12 |
| 13 import dgen_opt |
| 14 |
| 15 def generate_decoder(tables, out): |
| 16 """Entry point to the decoder. |
| 17 |
| 18 Args: |
| 19 tables: list of Table objects to process. |
| 20 out: a COutput object to write to. |
| 21 """ |
| 22 if len(tables) == 0: raise Exception('No tables provided.') |
| 23 |
| 24 _generate_header(out) |
| 25 out.line() |
| 26 out.line('namespace nacl_mips_dec {') |
| 27 out.line() |
| 28 _generate_decoder_state_type(tables, out) |
| 29 out.line() |
| 30 _generate_prototypes(tables, out) |
| 31 out.line() |
| 32 _generate_implementations(tables, out) |
| 33 out.line() |
| 34 _generate_init_function(out) |
| 35 out.line() |
| 36 _generate_entry_point(tables[0].name, out) |
| 37 out.line() |
| 38 out.line('} // namespace') |
| 39 |
| 40 def _generate_header(out): |
| 41 # TODO do we need a big ridiculous license banner in generated code? |
| 42 out.block_comment('DO NOT EDIT: GENERATED CODE') |
| 43 out.line('#include <stdio.h>') |
| 44 out.line('#include "native_client/src/trusted/validator_mips/decode.h"') |
| 45 |
| 46 |
| 47 def _generate_decoder_state_type(tables, out): |
| 48 out.block_comment( |
| 49 'This beast holds a bunch of pre-created ClassDecoder instances, which', |
| 50 'we create in init_decode(). Because ClassDecoders are stateless, we', |
| 51 'can freely reuse them -- even across threads -- and avoid allocating', |
| 52 'in the inner decoder loop.' |
| 53 ) |
| 54 terminals = set() |
| 55 for t in tables: |
| 56 for r in t.rows: |
| 57 if r.action.startswith('='): |
| 58 terminals.add(r.action[1:]) |
| 59 |
| 60 out.enter_block('struct DecoderState') |
| 61 |
| 62 for t in terminals: |
| 63 out.line('const %s _%s_instance;' % (t, t)) |
| 64 |
| 65 out.line('DecoderState() :') |
| 66 first = True |
| 67 for t in terminals: |
| 68 if first: |
| 69 out.line('_%s_instance()' % t) |
| 70 else: |
| 71 out.line(',_%s_instance()' % t) |
| 72 first = False |
| 73 out.line('{}') |
| 74 |
| 75 out.exit_block(';') |
| 76 |
| 77 |
| 78 def _generate_prototypes(tables, out): |
| 79 out.block_comment('Prototypes for static table-matching functions.') |
| 80 for t in tables: |
| 81 out.line('static inline const ClassDecoder &decode_%s(' |
| 82 'const Instruction insn, const DecoderState *state);' % t.name) |
| 83 |
| 84 def _generate_implementations(tables, out): |
| 85 out.block_comment('Table-matching function implementations.') |
| 86 for t in tables: |
| 87 out.line() |
| 88 _generate_table(t, out) |
| 89 |
| 90 |
| 91 def _generate_init_function(out): |
| 92 out.enter_block('const DecoderState *init_decode()') |
| 93 out.line('return new DecoderState;') |
| 94 out.exit_block() |
| 95 |
| 96 out.enter_block('void delete_state(const DecoderState *state)') |
| 97 out.line('delete (DecoderState *)state;') |
| 98 out.exit_block() |
| 99 |
| 100 def _generate_entry_point(initial_table_name, out): |
| 101 out.enter_block('const ClassDecoder &decode(const Instruction insn, ' |
| 102 'const DecoderState *state)') |
| 103 out.line('return decode_%s(insn, (DecoderState *)state);' |
| 104 % initial_table_name) |
| 105 out.exit_block() |
| 106 |
| 107 |
| 108 def _generate_table(table, out): |
| 109 """Generates the implementation of a single table.""" |
| 110 out.block_comment( |
| 111 'Implementation of table %s.' % table.name, |
| 112 'Specified by: %s.' % table.citation |
| 113 ) |
| 114 out.enter_block('static inline const ClassDecoder &decode_%s(' |
| 115 'const Instruction insn, const DecoderState *state)' % table.name) |
| 116 |
| 117 optimized = dgen_opt.optimize_rows(table.rows) |
| 118 print ("Table %s: %d rows minimized to %d" |
| 119 % (table.name, len(table.rows), len(optimized))) |
| 120 for row in sorted(optimized): |
| 121 exprs = ["(%s)" % p.to_c_expr('insn') for p in row.patterns] |
| 122 out.enter_block('if (%s)' % ' && '.join(exprs)) |
| 123 |
| 124 if row.action.startswith('='): |
| 125 _generate_terminal(row.action[1:], out) |
| 126 elif row.action.startswith('->'): |
| 127 _generate_table_change(row.action[2:], out) |
| 128 else: |
| 129 raise Exception('Bad table action: %s' % row.action) |
| 130 |
| 131 out.exit_block() |
| 132 out.line() |
| 133 |
| 134 _generate_safety_net(table, out) |
| 135 out.exit_block() |
| 136 |
| 137 |
| 138 def _generate_terminal(name, out): |
| 139 out.line('return state->_%s_instance;' % name) |
| 140 |
| 141 |
| 142 def _generate_table_change(name, out): |
| 143 out.line('return decode_%s(insn, state);' % name) |
| 144 |
| 145 |
| 146 def _generate_safety_net(table, out): |
| 147 out.line('// Catch any attempt to fall through...') |
| 148 out.line('fprintf(stderr, "TABLE IS INCOMPLETE: %s could not parse %%08X",' |
| 149 'insn.bits(31,0));' % table.name) |
| 150 _generate_terminal('Forbidden', out) |
| 151 |
| 152 |
| 153 class COutput(object): |
| 154 """Provides nicely-formatted C++ output.""" |
| 155 |
| 156 def __init__(self, out): |
| 157 self._out = out |
| 158 self._indent = 0 |
| 159 |
| 160 def line(self, str = ''): |
| 161 self._out.write(self._tabs()) |
| 162 self._out.write(str + '\n') |
| 163 |
| 164 def enter_block(self, headline): |
| 165 self.line(headline + ' {') |
| 166 self._indent += 1 |
| 167 |
| 168 def exit_block(self, footer = ''): |
| 169 self._indent -= 1 |
| 170 self.line('}' + footer) |
| 171 |
| 172 def block_comment(self, *lines): |
| 173 self.line('/*') |
| 174 for s in lines: |
| 175 self.line(' * ' + s) |
| 176 self.line(' */') |
| 177 |
| 178 def _tabs(self): |
| 179 return ' ' * self._indent |
| 180 |
| 181 |
| 182 def each_index_pair(sequence): |
| 183 """Utility method: Generates each unique index pair in sequence.""" |
| 184 for i in range(0, len(sequence)): |
| 185 for j in range(i + 1, len(sequence)): |
| 186 yield (i, j) |
| 187 |
| 188 |
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