python - 如何理解和解决PLY中的冲突-6ren

python - 如何理解和解决PLY中的冲突

转载作者：行者123 更新时间：2023-12-02 08:11:24

我正在使用SystemVerilog解析器，并且遇到许多层冲突（移位/减少和减少/减少）。

我目前有170多个冲突，而我的问题是我不太了解PLY生成的parser.out文件。在没有正确理解我无能为力的情况下，我的目标是了解帘布层报告的内容。所有PLY文档都是简短的，并且解释性不强。

在这里，您有我的一种状态，显然是第一种状态：

state 24

(134) attribute_instance_optional_list -> attribute_instance_list .
(136) attribute_instance_list -> attribute_instance_list . attribute_instance
(138) attribute_instance -> . LPAREN ASTERISK attr_spec_list ASTERISK RPAREN

  ! shift/reduce conflict for LPAREN resolved as shift
    PLUS            reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    MINUS           reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    EXCLAMATION     reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    NEG             reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    AMPERSAND       reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    NEGAMPERSAND    reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    PIPE            reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    NEGPIPE         reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    CARET           reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    NEGCARET        reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    UNBASED_UNSIZED_LITERAL reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    STRING_LITERAL  reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    REAL_FLOATINGP_NUMBER reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    REAL_FIXEDP_NUMBER reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    INT_HEX_NUMBER  reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    INT_BINARY_NUMBER reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    INT_OCTAL_NUMBER reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    INT_DECIMAL_NUMBER reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    UNSIGNED_NUMBER reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    DOUBLEPLUS      reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    DOUBLEMINUS     reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    AT              reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    TAGGED          reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    INOUT           reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    INPUT           reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    OUTPUT          reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    REF             reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    ID              reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    ESCAPED_ID      reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    MODULE          reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    MACROMODULE     reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .)
    LPAREN          shift and go to state 21

  ! LPAREN          [ reduce using rule 134 (attribute_instance_optional_list -> attribute_instance_list .) ]

    attribute_instance             shift and go to state 49

据我所知，语法规则被处理并且状态被建立。这些州中的每个州都根据即将到来的令牌做出决策。
因此，例如，在此状态下，我发布了状态24（状态24），如果PLUS令牌正等待在堆栈中移动，则层会继续前进并“使用规则134减少”。我不明白的一件事是，板层会做什么？我是说它保持相同的状态（24）？仅当“ attribute_instance”正等待移入，层实际移动到状态49时才出现吗？

另一个问题，在国家开始时列出的解析“快照”是什么意思？

(134) attribute_instance_optional_list -> attribute_instance_list .
(136) attribute_instance_list -> attribute_instance_list . attribute_instance
(138) attribute_instance -> . LPAREN ASTERISK attr_spec_list ASTERISK RPAREN

PLY是否计算可能达到状态24的所有可能的堆栈状态？那有可能吗？

如果有什么用，您可以在这里查看我的语法规则：

Grammar

Rule 0     S' -> source_text
Rule 1     source_text -> timeunits_declaration description_list
Rule 2     timeunits_declaration -> timeunit_and_precision
Rule 3     timeunits_declaration -> timeunit
Rule 4     timeunits_declaration -> timeprecision
Rule 5     timeunits_declaration -> timeunit timeprecision
Rule 6     timeunits_declaration -> timeprecision timeunit
Rule 7     timeunits_declaration -> empty
Rule 8     timeunit_and_precision -> TIMEUNIT time_literal SLASH time_literal SEMICOLON
Rule 9     timeunit -> TIMEUNIT time_literal SEMICOLON
Rule 10    timeprecision -> TIMEPRECISION time_literal SEMICOLON
Rule 11    time_literal -> UNSIGNED_NUMBER time_unit
Rule 12    time_literal -> REAL_FIXEDP_NUMBER time_unit
Rule 13    time_unit -> S
Rule 14    time_unit -> MS
Rule 15    time_unit -> US
Rule 16    time_unit -> NS
Rule 17    time_unit -> PS
Rule 18    time_unit -> FS
Rule 19    description_list -> description_list description
Rule 20    description_list -> description
Rule 21    description -> module_declaration
Rule 22    module_declaration -> module_nonansi_header timeunits_declaration module_item_list module_footer
Rule 23    module_declaration -> module_ansi_header timeunits_declaration non_port_module_item_list module_footer
Rule 24    module_declaration -> module_implicit_header timeunits_declaration module_item module_footer
Rule 25    module_declaration -> EXTERN module_nonansi_header
Rule 26    module_declaration -> EXTERN module_ansi_header
Rule 27    module_nonansi_header -> attribute_instance_optional_list module_keyword lifetime module_identifier package_import_declaration_list parameter_port_list list_of_ports SEMICOLON
Rule 28    module_ansi_header -> attribute_instance_optional_list module_keyword lifetime module_identifier package_import_declaration_list parameter_port_list list_of_port_declarations_list SEMICOLON
Rule 29    module_implicit_header -> attribute_instance_optional_list module_keyword lifetime module_identifier LPAREN DOT ASTERISK RPAREN SEMICOLON
Rule 30    module_keyword -> MODULE
Rule 31    module_keyword -> MACROMODULE
Rule 32    module_footer -> ENDMODULE COLON module_identifier
Rule 33    module_footer -> ENDMODULE
Rule 34    module_item -> port_declaration SEMICOLON
Rule 35    module_item -> non_port_module_item
Rule 36    port_declaration -> attribute_instance_optional_list inout_declaration
Rule 37    port_declaration -> attribute_instance_optional_list input_declaration
Rule 38    port_declaration -> attribute_instance_optional_list output_declaration
Rule 39    port_declaration -> attribute_instance_optional_list ref_declaration
Rule 40    port_declaration -> attribute_instance_optional_list interface_port_declaration
Rule 41    inout_declaration -> INOUT net_port_type list_of_port_identifiers
Rule 42    input_declaration -> INPUT net_port_type list_of_port_identifiers
Rule 43    input_declaration -> INPUT variable_port_type list_of_variable_identifiers
Rule 44    output_declaration -> OUTPUT net_port_type list_of_port_identifiers
Rule 45    interface_port_declaration -> interface_identifier list_of_interface_identifiers
Rule 46    interface_port_declaration -> interface_identifier DOT modport_identifier list_of_interface_identifiers
Rule 47    ref_declaration -> REF variable_port_type list_of_variable_identifiers
Rule 48    casting_type -> simple_type
Rule 49    casting_type -> constant_primary
Rule 50    casting_type -> signing
Rule 51    casting_type -> STRING
Rule 52    casting_type -> CONST
Rule 53    data_type -> integer_vector_type optional_signing optional_packed_dimension
Rule 54    data_type -> integer_atom_type optional_signing
Rule 55    data_type -> non_integer_type
Rule 56    data_type -> struct_union LBRACE struct_union_member_list RBRACE optional_packed_dimension_list
Rule 57    data_type -> ENUM LBRACE optional_enum_name_declaration_list RBRACE optional_packed_dimension_list
Rule 58    data_type -> ENUM enum_base_type LBRACE optional_enum_name_declaration_list RBRACE optional_packed_dimension_list
Rule 59    data_type -> STRING
Rule 60    data_type -> CHANDLE
Rule 61    data_type -> VIRTUAL interface_identifier optional_parameter_value_assignment optional_modport_identifier
Rule 62    data_type -> VIRTUAL INTERFACE interface_identifier optional_parameter_value_assignment optional_modport_identifier
Rule 63    data_type -> type_identifier optional_packed_dimension_list
Rule 64    data_type -> class_scope type_identifier optional_packed_dimension_list
Rule 65    data_type -> package_scope type_identifier optional_packed_dimension_list
Rule 66    data_type -> class_type
Rule 67    data_type -> EVENT
Rule 68    data_type -> ps_covergroup_identifier
Rule 69    data_type -> type_reference
Rule 70    data_type_or_implicit -> data_type
Rule 71    data_type_or_implicit -> implicit_data_type
Rule 72    implicit_data_type -> optional_signing optional_packed_dimension_list
Rule 73    enum_base_type -> integer_atom_type optional_signing
Rule 74    enum_base_type -> integer_vector_type optional_signing optional_packed_dimension
Rule 75    enum_base_type -> type_identifier optional_packed_dimension
Rule 76    enum_name_declaration -> enum_identifier optional_enum_identifier_pointer
Rule 77    enum_name_declaration -> enum_identifier optional_enum_identifier_pointer EQUALS constant_expression
Rule 78    optional_enum_identifier_pointer -> LBRACKET integral_number RBRACKET
Rule 79    optional_enum_identifier_pointer -> LBRACKET integral_number COLON integral_number RBRACKET
Rule 80    optional_enum_identifier_pointer -> empty
Rule 81    class_scope -> class_type DOUBLECOLON
Rule 82    class_type -> ps_class_identifier optional_parameter_value_assignment
Rule 83    class_type -> ps_class_identifier optional_parameter_value_assignment parametrized_class_list
Rule 84    parametrized_class_list -> parametrized_class_list DOUBLECOLON class_identifier optional_parameter_value_assignment
Rule 85    parametrized_class_list -> DOUBLECOLON class_identifier optional_parameter_value_assignment
Rule 86    integer_type -> integer_vector_type
Rule 87    integer_type -> integer_atom_type
Rule 88    integer_atom_type -> BYTE
Rule 89    integer_atom_type -> SHORTINT
Rule 90    integer_atom_type -> INT
Rule 91    integer_atom_type -> LONGINT
Rule 92    integer_atom_type -> INTEGER
Rule 93    integer_atom_type -> TIME
Rule 94    integer_vector_type -> BIT
Rule 95    integer_vector_type -> LOGIC
Rule 96    integer_vector_type -> REG
Rule 97    non_integer_type -> SHORTREAL
Rule 98    non_integer_type -> REAL
Rule 99    non_integer_type -> REALTIME
Rule 100   net_type -> SUPPLY0
Rule 101   net_type -> SUPPLY1
Rule 102   net_type -> TRI
Rule 103   net_type -> TRIAND
Rule 104   net_type -> TRIOR
Rule 105   net_type -> TRIREG
Rule 106   net_type -> TRI0
Rule 107   net_type -> TRI1
Rule 108   net_type -> UWIRE
Rule 109   net_type -> WIRE
Rule 110   net_type -> WAND
Rule 111   net_type -> WOR
Rule 112   net_port_type -> data_type_or_implicit
Rule 113   net_port_type -> net_type data_type_or_implicit
Rule 114   net_port_type -> net_type_identifier
Rule 115   net_port_type -> INTERCONNECT implicit_data_type
Rule 116   variable_port_type -> var_data_type
Rule 117   var_data_type -> data_type
Rule 118   var_data_type -> VAR data_type_or_implicit
Rule 119   signing -> SIGNED
Rule 120   signing -> UNSIGNED
Rule 121   simple_type -> integer_type
Rule 122   simple_type -> non_integer_type
Rule 123   simple_type -> ps_type_identifier
Rule 124   simple_type -> ps_parameter_identifier
Rule 125   struct_union_member -> attribute_instance_optional_list data_type_or_void list_of_variable_decl_assignments
Rule 126   struct_union_member -> attribute_instance_optional_list random_qualifier data_type_or_void list_of_variable_decl_assignments
Rule 127   data_type_or_void -> data_type
Rule 128   data_type_or_void -> VOID
Rule 129   struct_union -> STRUCT
Rule 130   struct_union -> UNION
Rule 131   struct_union -> UNION TAGGED
Rule 132   type_reference -> TYPE LPAREN expression RPAREN
Rule 133   type_reference -> TYPE LPAREN data_type RPAREN
Rule 134   attribute_instance_optional_list -> attribute_instance_list
Rule 135   attribute_instance_optional_list -> empty
Rule 136   attribute_instance_list -> attribute_instance_list attribute_instance
Rule 137   attribute_instance_list -> attribute_instance
Rule 138   attribute_instance -> LPAREN ASTERISK attr_spec_list ASTERISK RPAREN
Rule 139   attr_spec_list -> attr_spec_list COMMA attr_spec
Rule 140   attr_spec_list -> attr_spec
Rule 141   attr_spec -> attr_name
Rule 142   attr_spec -> attr_name EQUALS constant_expression
Rule 143   attr_name -> identifier
Rule 144   inc_or_dec_expression -> inc_or_dec_operator attribute_instance_optional_list variable_lvalue
Rule 145   inc_or_dec_expression -> variable_lvalue attribute_instance_optional_list inc_or_dec_operator
Rule 146   conditional_expression -> cond_predicate INTERROGATION attribute_instance_optional_list expression COLON expression
Rule 147   constant_expression -> constant_primary
Rule 148   constant_expression -> unary_operator attribute_instance_optional_list constant_primary
Rule 149   constant_expression -> constant_expression binary_operator attribute_instance_optional_list constant_expression
Rule 150   constant_expression -> constant_expression INTERROGATION attribute_instance_optional_list constant_expression COLON constant_expression
Rule 151   constant_mintypmax_expression -> constant_expression
Rule 152   constant_mintypmax_expression -> constant_expression COLON constant_expression COLON constant_expression
Rule 153   constant_param_expression -> constant_mintypmax_expression
Rule 154   constant_param_expression -> data_type
Rule 155   constant_param_expression -> DOLLAR
Rule 156   param_expression -> mintypmax_expression
Rule 157   param_expression -> data_type
Rule 158   param_expression -> DOLLAR
Rule 159   constant_range_expression -> constant_expression
Rule 160   constant_range_expression -> constant_part_select_range
Rule 161   constant_part_select_range -> constant_range
Rule 162   constant_part_select_range -> constant_indexed_range
Rule 163   constant_range -> constant_expression COLON constant_expression
Rule 164   constant_indexed_range -> constant_expression PLUSCOLON constant_expression
Rule 165   constant_indexed_range -> constant_expression MINUSCOLON constant_expression
Rule 166   expression -> primary
Rule 167   expression -> unary_operator attribute_instance_optional_list primary
Rule 168   expression -> inc_or_dec_expression
Rule 169   expression -> LPAREN operator_assignment RPAREN
Rule 170   expression -> expression binary_operator attribute_instance_optional_list expression
Rule 171   expression -> conditional_expression
Rule 172   expression -> inside_expression
Rule 173   expression -> tagged_union_expression
Rule 174   tagged_union_expression -> TAGGED member_identifier
Rule 175   tagged_union_expression -> TAGGED member_identifier expression
Rule 176   inside_expression -> expression INSIDE LBRACE open_range_list RBRACE
Rule 177   value_range -> expression
Rule 178   value_range -> LBRACKET expression COLON expression RBRACKET
Rule 179   mintypmax_expression -> expression
Rule 180   mintypmax_expression -> expression COLON expression COLON expression
Rule 181   module_path_conditional_expression -> module_path_expression INTERROGATION attribute_instance_optional_list module_path_expression COLON module_path_expression
Rule 182   module_path_expression -> module_path_primary
Rule 183   module_path_expression -> unary_module_path_operator attribute_instance_optional_list module_path_primary
Rule 184   module_path_expression -> module_path_expression binary_module_path_operator attribute_instance_optional_list module_path_expression
Rule 185   module_path_expression -> module_path_conditional_expression
Rule 186   module_path_mintypmax_expression -> module_path_expression
Rule 187   module_path_mintypmax_expression -> module_path_expression COLON module_path_expression COLON module_path_expression
Rule 188   part_select_range -> constant_range
Rule 189   part_select_range -> indexed_range
Rule 190   indexed_range -> expression PLUSCOLON constant_expression
Rule 191   indexed_range -> expression MINUSCOLON constant_expression
Rule 192   genvar_expression -> constant_expression
Rule 193   constant_primary -> primary_literal
Rule 194   primary_literal -> number
Rule 195   primary_literal -> time_literal
Rule 196   primary_literal -> UNBASED_UNSIZED_LITERAL
Rule 197   primary_literal -> STRING_LITERAL
Rule 198   number -> REAL_FLOATINGP_NUMBER
Rule 199   number -> REAL_FIXEDP_NUMBER
Rule 200   number -> INT_HEX_NUMBER
Rule 201   number -> INT_BINARY_NUMBER
Rule 202   number -> INT_OCTAL_NUMBER
Rule 203   number -> INT_DECIMAL_NUMBER
Rule 204   number -> UNSIGNED_NUMBER
Rule 205   unary_operator -> PLUS
Rule 206   unary_operator -> MINUS
Rule 207   unary_operator -> EXCLAMATION
Rule 208   unary_operator -> NEG
Rule 209   unary_operator -> AMPERSAND
Rule 210   unary_operator -> NEGAMPERSAND
Rule 211   unary_operator -> PIPE
Rule 212   unary_operator -> NEGPIPE
Rule 213   unary_operator -> CARET
Rule 214   unary_operator -> NEGCARET
Rule 215   binary_operator -> PLUS
Rule 216   binary_operator -> MINUS
Rule 217   binary_operator -> ASTERISK
Rule 218   binary_operator -> SLASH
Rule 219   binary_operator -> PERCENT
Rule 220   binary_operator -> ISEQUAL
Rule 221   binary_operator -> NISEQUAL
Rule 222   binary_operator -> CISEQUAL
Rule 223   binary_operator -> NCISEQUAL
Rule 224   binary_operator -> WISEQUAL
Rule 225   binary_operator -> NWISEQUAL
Rule 226   binary_operator -> DOUBLEAMPERSAND
Rule 227   binary_operator -> DOUBLEPIPE
Rule 228   binary_operator -> DOUBLEASTERISK
Rule 229   binary_operator -> LT
Rule 230   binary_operator -> LE
Rule 231   binary_operator -> GT
Rule 232   binary_operator -> GE
Rule 233   binary_operator -> AMPERSAND
Rule 234   binary_operator -> PIPE
Rule 235   binary_operator -> CARET
Rule 236   binary_operator -> NEGCARET
Rule 237   binary_operator -> RSHIFT
Rule 238   binary_operator -> LSHIFT
Rule 239   binary_operator -> ARSHIFT
Rule 240   binary_operator -> ALSHIFT
Rule 241   binary_operator -> IMPLICATION
Rule 242   binary_operator -> EQUIVALENCE
Rule 243   inc_or_dec_operator -> DOUBLEPLUS
Rule 244   inc_or_dec_operator -> DOUBLEMINUS
Rule 245   unary_module_path_operator -> EXCLAMATION
Rule 246   unary_module_path_operator -> NEG
Rule 247   unary_module_path_operator -> AMPERSAND
Rule 248   unary_module_path_operator -> NEGAMPERSAND
Rule 249   unary_module_path_operator -> PIPE
Rule 250   unary_module_path_operator -> NEGPIPE
Rule 251   unary_module_path_operator -> CARET
Rule 252   unary_module_path_operator -> NEGCARET
Rule 253   binary_module_path_operator -> ISEQUAL
Rule 254   binary_module_path_operator -> NISEQUAL
Rule 255   binary_module_path_operator -> DOUBLEAMPERSAND
Rule 256   binary_module_path_operator -> DOUBLEPIPE
Rule 257   binary_module_path_operator -> AMPERSAND
Rule 258   binary_module_path_operator -> PIPE
Rule 259   binary_module_path_operator -> CARET
Rule 260   binary_module_path_operator -> NEGCARET
Rule 261   array_identifier -> identifier
Rule 262   block_identifier -> identifier
Rule 263   bin_identifier -> identifier
Rule 264   c_identifier -> C_ID
Rule 265   cell_identifier -> identifier
Rule 266   checker_identifier -> identifier
Rule 267   class_identifier -> identifier
Rule 268   class_variable_identifier -> variable_identifier
Rule 269   clocking_identifier -> identifier
Rule 270   config_identifier -> identifier
Rule 271   const_identifier -> identifier
Rule 272   constraint_identifier -> identifier
Rule 273   covergroup_identifier -> identifier
Rule 274   covergroup_variable_identifier -> variable_identifier
Rule 275   cover_point_identifier -> identifier
Rule 276   cross_identifier -> identifier
Rule 277   dynamic_array_variable_identifier -> variable_identifier
Rule 278   enum_identifier -> identifier
Rule 279   escaped_identifier -> ESCAPED_ID
Rule 280   formal_identifier -> identifier
Rule 281   formal_port_identifier -> identifier
Rule 282   function_identifier -> identifier
Rule 283   generate_block_identifier -> identifier
Rule 284   genvar_identifier -> identifier
Rule 285   hierarchical_array_identifier -> hierarchical_identifier
Rule 286   hierarchical_block_identifier -> hierarchical_identifier
Rule 287   hierarchical_event_identifier -> hierarchical_identifier
Rule 288   hierarchical_identifier -> optional_identifier_constant_bit_select_list identifier
Rule 289   hierarchical_identifier -> DOLLAR ROOT DOT optional_identifier_constant_bit_select_list identifier
Rule 290   hierarchical_net_identifier -> hierarchical_identifier
Rule 291   hierarchical_parameter_identifier -> hierarchical_identifier
Rule 292   hierarchical_property_identifier -> hierarchical_identifier
Rule 293   hierarchical_sequence_identifier -> hierarchical_identifier
Rule 294   hierarchical_task_identifier -> hierarchical_identifier
Rule 295   hierarchical_tf_identifier -> hierarchical_identifier
Rule 296   hierarchical_variable_identifier -> hierarchical_identifier
Rule 297   identifier -> simple_identifier
Rule 298   identifier -> escaped_identifier
Rule 299   index_variable_identifier -> identifier
Rule 300   interface_identifier -> identifier
Rule 301   interface_instance_identifier -> identifier
Rule 302   inout_port_identifier -> identifier
Rule 303   input_port_identifier -> identifier
Rule 304   instance_identifier -> identifier
Rule 305   library_identifier -> identifier
Rule 306   member_identifier -> identifier
Rule 307   method_identifier -> identifier
Rule 308   modport_identifier -> identifier
Rule 309   module_identifier -> identifier
Rule 310   net_identifier -> identifier
Rule 311   net_type_identifier -> identifier
Rule 312   output_port_identifier -> identifier
Rule 313   package_identifier -> identifier
Rule 314   package_scope -> package_identifier DOUBLECOLON
Rule 315   package_scope -> DOLLAR UNIT DOUBLECOLON
Rule 316   optional_package_scope -> package_scope
Rule 317   optional_package_scope -> empty
Rule 318   parameter_identifier -> identifier
Rule 319   port_identifier -> identifier
Rule 320   production_identifier -> identifier
Rule 321   program_identifier -> identifier
Rule 322   property_identifier -> identifier
Rule 323   ps_class_identifier -> optional_package_scope class_identifier
Rule 324   ps_covergroup_identifier -> optional_package_scope covergroup_identifier
Rule 325   ps_checker_identifier -> optional_package_scope checker_identifier
Rule 326   ps_identifier -> optional_package_scope identifier
Rule 327   ps_or_hierarchical_array_identifier -> optional_package_scope hierarchical_array_identifier
Rule 328   ps_or_hierarchical_array_identifier -> implicit_class_handle DOT hierarchical_array_identifier
Rule 329   ps_or_hierarchical_array_identifier -> class_scope hierarchical_array_identifier
Rule 330   ps_or_hierarchical_net_identifier -> optional_package_scope net_identifier
Rule 331   ps_or_hierarchical_net_identifier -> hierarchical_net_identifier
Rule 332   ps_or_hierarchical_property_identifier -> optionnal_package_scope property_identifier
Rule 333   ps_or_hierarchical_property_identifier -> hierarchical_property_identifier
Rule 334   ps_or_hierarchical_sequence_identifier -> optional_package_scope sequence_identifier
Rule 335   ps_or_hierarchical_sequence_identifier -> hierarchical_sequence_identifier
Rule 336   ps_or_hierarchical_tf_identifier -> optional_package_scope tf_identifier
Rule 337   ps_or_hierarchical_tf_identifier -> hierarchical_tf_identifier
Rule 338   ps_parameter_identifier -> optional_package_scope parameter_identifier
Rule 339   ps_parameter_identifier -> class_scope parameter_identifier
Rule 340   ps_parameter_identifier -> ps_parameter_identifier_generate_list parameter_identifier
Rule 341   ps_parameter_identifier_generate_list -> ps_parameter_identifier_generate_list DOT ps_parameter_identifier_generate
Rule 342   ps_parameter_identifier_generate_list -> ps_parameter_identifier_generate
Rule 343   ps_parameter_identifier_generate -> generate_block_identifier LBRACKET constant_expression RBRACKET
Rule 344   ps_parameter_identifier_generate -> generate_block_identifier
Rule 345   ps_type_identifier -> type_identifier
Rule 346   ps_type_identifier -> LOCAL DOUBLECOLON type_identifier
Rule 347   ps_type_identifier -> package_scope type_identifier
Rule 348   sequence_identifier -> identifier
Rule 349   signal_identifier -> identifier
Rule 350   simple_identifier -> ID
Rule 351   specparam_identifier -> identifier
Rule 352   system_tf_identifier -> DOLLAR ID
Rule 353   task_identifier -> identifier
Rule 354   tf_identifier -> identifier
Rule 355   terminal_identifier -> identifier
Rule 356   topmodule_identifier -> identifier
Rule 357   type_identifier -> identifier
Rule 358   udp_identifier -> identifier
Rule 359   variable_identifier -> identifier
Rule 360   cond_predicate -> AT
Rule 361   implicit_class_handle -> AT
Rule 362   integral_number -> AT
Rule 363   lifetime -> AT
Rule 364   list_of_interface_identifiers -> AT
Rule 365   list_of_port_declarations_list -> AT
Rule 366   list_of_port_identifiers -> AT
Rule 367   list_of_ports -> AT
Rule 368   list_of_variable_decl_assignments -> AT
Rule 369   list_of_variable_identifiers -> AT
Rule 370   module_item_list -> AT
Rule 371   module_path_primary -> AT
Rule 372   non_port_module_item -> AT
Rule 373   non_port_module_item_list -> AT
Rule 374   open_range_list -> AT
Rule 375   operator_assignment -> AT
Rule 376   optional_enum_name_declaration_list -> AT
Rule 377   optional_identifier_constant_bit_select_list -> AT
Rule 378   optional_modport_identifier -> AT
Rule 379   optional_packed_dimension -> AT
Rule 380   optional_packed_dimension_list -> AT
Rule 381   optional_parameter_value_assignment -> AT
Rule 382   optional_signing -> AT
Rule 383   optionnal_package_scope -> AT
Rule 384   package_import_declaration_list -> AT
Rule 385   parameter_port_list -> AT
Rule 386   primary -> AT
Rule 387   random_qualifier -> AT
Rule 388   struct_union_member_list -> AT
Rule 389   variable_lvalue -> AT
Rule 390   empty -> <empty>

最佳答案

在LR解析中，我们经常谈论“项目”：一个项目是带有进度标记的产品，通常用•编写，但有时用简单的.编写。状态只是项目的集合。实际上，状态告诉您解析可能在内部的一组生产。

有一种特别特殊的项目类型：末尾带有点的项目：

(134) attribute_instance_optional_list -> attribute_instance_list .

由于进度标记位于末尾，因此代表可以完成的生产。如果这是正确的生产方式，则解析器必须将右侧替换为左侧：这是称为“减少”的操作（因为这与“生产”相反，即“生产”生产”）。

但是，仅处于可能减少状态的事实并不意味着减少是可能的。还必须使下一个令牌与减少的结果一致。如果下一个令牌不能跟随缩减的非终结符（在解析器状态的上下文中），则无法执行缩减，因此解析器将尝试进行移位（如果可能的话）。

换班很简单。如果状态中的一个或多个项目在当前前瞻符号之前带有点，则可以进行转换。在这里，毫无疑问要进行额外的超前查询，因为Ply（像许多LALR解析器生成器一样）仅创建LALR（1）解析器，该解析器在任何状态下都只有一个超前查询，因此我们唯一要做的就是当前使用的符号看起来很明显，只有在某些可用商品的下一个位置带有该符号的情况下，我们才可以对其进行处理。

如果具有给定超前符号的给定状态既可以平移又可以减少，那么您将发生平移减少冲突；解析器不知道该怎么办。（如果它既没有移位也没有减少量，则表明输入存在语法错误。这就是LR解析器识别语法错误的方式。）

LR解析的一个重要方面是，如果要完全执行还原操作，则必须立即执行还原操作。也就是说，如果我们处于可能的缩减状态，并且该项目的前瞻集表明前瞻字符是可行的，则必须执行缩减。我们迫不及待地想知道以后是否有可能，因为没有减少的机会了。换句话说，项目中•左侧的任何内容都已尽可能减少。（这是 R解析中的 LR，它表示每个归约都是“最右边的”。如果使用“最右边的”没有意义，请不要担心；我只提到了这个事实，以防万一你在想）

我可能还要提到的另一件事是，在LALR解析（“ Lookahead LR解析”）中，状态是由一组项精确定义的。每个项目都有一个适用的前瞻集，但是前瞻集不构成该州身份的一部分。如果解析器生成器最终产生具有相同项目但具有不同前瞻集的两个状态，则它必须将它们合并为一个状态，从而形成每个前瞻集的并集。对于完整的LR解析，此限制不存在。对于给定的一组项目，您可以（并且确实）具有多个状态，结果是解析表要大得多，功能也要稍微强一些。

现在，如果可以进行换档操作，则可以机械地确定换档后哪个状态将处于活动状态。例如，来自

(134) attribute_instance_optional_list -> attribute_instance_list .
(136) attribute_instance_list -> attribute_instance_list . attribute_instance
(138) attribute_instance -> . LPAREN ASTERISK attr_spec_list ASTERISK RPAREN

移位 LPAREN后，下一个状态将只有一项：

(138) attribute_instance -> LPAREN . ASTERISK attr_spec_list ASTERISK RPAREN

（请注意点的移动方式。）

这是一个简单的情况，因为下一个符号是终端 ASTERISK。在大多数情况下，移位后的下一个符号将是一个非终止符，在这种情况下，我们需要添加该非终止符的所有乘积，并在其开头加点。（这就是状态最终包含多个项的方式。）因此，例如，给定一个新状态有一个项并输入 ASTERISK（其他任何情况都会出错，因为该状态没有还原的可能性），然后我们将转移到具有已转移项目的状态：

(138) attribute_instance -> LPAREN ASTERISK . attr_spec_list ASTERISK RPAREN

加上 attr_spec_list的所有作品：

(139)   attr_spec_list -> . attr_spec_list COMMA attr_spec
(140)   attr_spec_list -> . attr_spec

加上 attr_spec的所有作品（因为我们刚刚在 attr_spec之前添加了带点的项目）：

(141)   attr_spec -> . attr_name
(142)   attr_spec -> . attr_name EQUALS constant_expression

加上 attr_name的产量：

(143)   attr_name -> . identifier

以此类推，直到我们停止看到新的非终端为止：

(297)   identifier -> . simple_identifier
(298)   identifier -> . escaped_identifier
(350)   simple_identifier -> . ID
(279)   escaped_identifier -> . ESCAPED_ID

好，现在下一个令牌将必须为 ID或 ESCAPED_ID。假设它是 ID。怎么办？好吧，我们将进入一个状态

(350)   simple_identifier -> ID .

可能减少；假设先行符号与先行集合匹配（我没有也不想解释如何为每种状态计算先行集合；有一种算法，但此处不涉及细节），则 ID将被简化到 simple_identifier。那么解析器去哪儿了？从逻辑上讲，它返回到生成 simple_identifier生产的状态，并移动 simple_identifier。碰巧的是，状态就是我们刚刚创建的状态

(138)   attribute_instance -> LPAREN ASTERISK . attr_spec_list ASTERISK RPAREN
(139)   attr_spec_list -> . attr_spec_list COMMA attr_spec
(140)   attr_spec_list -> . attr_spec
(141)   attr_spec -> . attr_name
(142)   attr_spec -> . attr_name EQUALS constant_expression
(143)   attr_name -> . identifier
(297)   identifier -> . simple_identifier
(298)   identifier -> . escaped_identifier
(350)   simple_identifier -> . ID
(279)   escaped_identifier -> . ESCAPED_ID

在移动 simple_identifier之后，我们最终得到

(297)   identifier -> simple_identifier .

这是一个需要减少到 identifier的状态，因此再次回到同一状态之后，我们发现自己处于

(143)   attr_name -> identifier .

然后

(141)   attr_spec -> attr_name .
(142)   attr_spec -> attr_name . EQUALS constant_expression

但是，解析器如何知道这些缩减中的每一个返回哪个状态？答案是解析器将当前状态与每个符号一起推送到解析堆栈。进行归约时，它将从右侧弹出符号，并丢弃每个关联的状态编号，直到到达右侧的开头为止，此时堆栈会指示右侧的状态来自。然后，它查看该状态，移动简化的非终结符，然后将新的移动状态推入解析堆栈。

因此，我认为这回答了以下问题：“状态描述开头的行是什么意思？”和“简化后解析器将进入什么状态？”其他两个问题很容易回答：“不，它不会计算所有可能的前任状态”，“是，它可以（尽管最终可能会添加任何输入实际上不可能实现的前任状态），但事实并非如此。对于解析没有用。”但是由于它们与解决减少班次冲突并没有十分重要的关系，因此我将不作进一步解释。

回到实际的班次减少冲突，情况是我们处于状态

(134) attribute_instance_optional_list -> attribute_instance_list .
(136) attribute_instance_list -> attribute_instance_list . attribute_instance
(138) attribute_instance -> . LPAREN ASTERISK attr_spec_list ASTERISK RPAREN

可能会有减少，并且我们正在考虑看到 LPAREN的情况，该情况可能存在偏移，事实证明，为第一项设置的超前预测还包括 LPAREN。尽管前瞻集未显示在PLY输出中，但是我们可以在语法中进行挖掘以查看它可能来自何处。当然，直接来源是 attribute_instance_optional_list，尽管有很多可能性，我们可以在语法中发现：

(27)    module_nonansi_header -> attribute_instance_optional_list module_keyword lifetime module_identifier package_import_declaration_list parameter_port_list list_of_ports SEMICOLON
(28)    module_ansi_header -> attribute_instance_optional_list module_keyword lifetime module_identifier package_import_declaration_list parameter_port_list list_of_port_declarations_list SEMICOLON
(29)    module_implicit_header -> attribute_instance_optional_list module_keyword lifetime module_identifier LPAREN DOT ASTERISK RPAREN SEMICOLON
(36)    port_declaration -> attribute_instance_optional_list inout_declaration
(37)    port_declaration -> attribute_instance_optional_list input_declaration
(38)    port_declaration -> attribute_instance_optional_list output_declaration
(39)    port_declaration -> attribute_instance_optional_list ref_declaration
(40)    port_declaration -> attribute_instance_optional_list interface_port_declaration
(125)   struct_union_member -> attribute_instance_optional_list data_type_or_void list_of_variable_decl_assignments
(126)   struct_union_member -> attribute_instance_optional_list random_qualifier data_type_or_void list_of_variable_decl_assignments
(144)   inc_or_dec_expression -> inc_or_dec_operator attribute_instance_optional_list variable_lvalue
(145)   inc_or_dec_expression -> variable_lvalue attribute_instance_optional_list inc_or_dec_operator
(146)   conditional_expression -> cond_predicate INTERROGATION attribute_instance_optional_list expression COLON expression
(148)   constant_expression -> unary_operator attribute_instance_optional_list constant_primary
(149)   constant_expression -> constant_expression binary_operator attribute_instance_optional_list constant_expression
(150)   constant_expression -> constant_expression INTERROGATION attribute_instance_optional_list constant_expression COLON constant_expression
(167)   expression -> unary_operator attribute_instance_optional_list primary
(170)   expression -> expression binary_operator attribute_instance_optional_list expression
(181)   module_path_conditional_expression -> module_path_expression INTERROGATION attribute_instance_optional_list module_path_expression COLON module_path_expression
(183)   module_path_expression -> unary_module_path_operator attribute_instance_optional_list module_path_primary
(184)   module_path_expression -> module_path_expression binary_module_path_operator attribute_instance_optional_list module_path_expression

据我所知， attribute_instance_optional_list不会出现在所有这些结果的末尾，从而简化了 LPAREN冲突的出处。在所有这些情况下，其后都是非终结符，可能是：

module_keyword
inout_declaration
input_declaration
output_declaration
ref_declaration
interface_port_declaration
data_type_or_void
random_qualifier
variable_lvalue
inc_or_dec_operator
constant_primary
constant_expression
primary
expression
module_path_primary
module_path_expression

现在，如果这些非终结符中的任何一个可以以 LPAREN开头，那么我们就有可能发生移位减少冲突。有几个罪魁祸首从列表中跳出： expression和类似的东西。

因此，总而言之，这里存在一个问题： attribute_instance可以以括号开头，但是 attribute_instance_list也可以以括号开头。因此，当您位于attribute_instance_list的中间并且看到一个（时，您将无法知道是移动还是缩小。

关于python - 如何理解和解决PLY中的冲突，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/41775631/

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python - 如何理解和解决PLY中的冲突