Skip to content

Commit

Permalink
documentation converision to sphinx
Browse files Browse the repository at this point in the history
  • Loading branch information
Dibyendu Majumdar committed Feb 7, 2015
1 parent 7583b66 commit 125e084
Showing 1 changed file with 77 additions and 8 deletions.
85 changes: 77 additions & 8 deletions readthedocs/lua-parser.rst
View file
Original file line number Diff line number Diff line change
Expand Up @@ -366,14 +366,83 @@ State Transitions
-----------------
The state transitions for ``expdesc`` structure are as follows:

expkind | Description | State Transitions
------------------ | ---------------------------------------| -----------------
``VVOID`` | This is used to indicate the lack of value - e.g. function call with no arguments, the rhs of local variable declaration, and empty table constructor | None
``VRELOCABLE`` | This is used to indicate that the result from expression needs to be set to a register. The operation that created the expression is referenced by the ``u.info`` parameter which contains an offset into the ``code`` of the function that is being compiled. So you can access this instruction by calling ``getcode(FuncState *, expdesc *)`` The operations that result in a ``VRELOCABLE`` object include ``OP_CLOSURE`` ``OP_NEWTABLE`` ``OP_GETUPVAL`` ``OP_GETTABUP`` ``OP_GETTABLE`` ``OP_NOT`` and code for binary and unary expressions that produce values (arithmetic operations, bitwise operations, concat, length). The associated code instruction has operand ``A`` unset (defaulted to 0) - this the ``VRELOCABLE`` expression must be later transitioned to ``VNONRELOC`` state when the register is set. | In terms of transitions the following expression kinds convert to ``VRELOCABLE``: ``VVARARG`` ``VUPVAL`` (``OP_GETUPVAL`` ``VINDEXED`` (``OP_GETTABUP`` or ``OP_GETTABLE`` And following expression states can result from a ``VRELOCABLE`` expression: ``VNONRELOC`` which means that the result register in the instruction operand A has been set.
``VNONRELOC`` | This state indicates that the output or result register has been set. The register is referenced in ``u.info`` parameter. Once set the register cannot be changed for this expression - subsequent operations involving this expression can refer to the register to obtain the result value. | As for transitions, the ``VNONELOC`` state results from ``VRELOCABLE`` after a register is assigned to the operation referenced by ``VRELOCABLE`` Also a ``VCALL`` expression transitions to ``VNONRELOC`` expression - ``u.info`` is set to the operand ``A`` of the associated call instruction. ``VLOCAL`` ``VNIL`` ``VTRUE`` ``VFALSE`` ``VK`` ``VKINT`` ``VKFLT`` and ``VJMP`` expressions transition to ``VNONRELOC``
``VLOCAL`` | This is used when referencing local variables. ``u.info`` is set to the local variable's register. | The ``VLOCAL`` expression may transition to ``VNONRELOC`` although this doesn't change the ``u.info`` parameter.
``VCALL`` | This results from a function call. The ``OP_CALL`` instruction is referenced by ``u.info`` parameter and may be retrieved by calling ``getcode(FuncState *, expdesc *)`` The ``OP_CALL`` instruction gets changed to ``OP_TAILCALL`` if the function call expression is the value of a ``RETURN`` statement. The instructions operand ``C`` gets updated when it is known the number of expected results from the function call. | In terms of transitions, the ``VCALL`` expression transitions to ``VNONRELOC`` When this happens the result register in ``VNONRELOC`` (``u.info`` is set to the operand ``A`` in the ``OP_CALL`` instruction.
``VINDEXED`` | This expression represents a table access. The ``u.ind.t`` parameter is set to the register or upvalue? that holds the table, the ``u.ind.idx`` is set to the register or constant that is the key, and ``u.ind.vt`` is either ``VLOCAL`` or ``VUPVAL`` | The ``VINDEXED`` expression transitions to ``VRELOCABLE`` When this happens the ``u.info`` is set to the offset of the code that contains the opcode ``OP_GETTABUP`` if ``u.ind.vt`` was ``VUPVAL`` or ``OP_GETTABLE`` if ``u.ind.vt`` was ``VLOCAL``
+------------------|----------------------------------------|------------------------------------+
| expkind | Description | State Transitions |
+==================+========================================+====================================+
|``VVOID`` | This is used to indicate the lack of | None |
| | value - e.g. function call with no | |
| | arguments, the rhs of local variable | |
| | declaration, and empty table | |
| | constructor | |
+------------------+----------------------------------------+------------------------------------+
|``VRELOCABLE`` | This is used to indicate that the | In terms of transitions the |
| | result from expression needs to be set | following expression kinds convert |
| | to a register. The operation that | to ``VRELOCABLE``: ``VVARARG`` |
| | created the expression is referenced | ``VUPVAL`` (``OP_GETUPVAL`` |
| | by the ``u.info`` parameter which | ``VINDEXED`` (``OP_GETTABUP`` or |
| | contains an offset into the ``code`` | ``OP_GETTABLE`` And following |
| | of the function that is being compiled.| expression states can result from |
| | So you can access this instruction by | a ``VRELOCABLE`` expression: |
| | calling | ``VNONRELOC`` which |
| | ``getcode(FuncState *, expdesc *)`` | means that the result register in |
| | The operations that result in a | the instruction operand A has been |
| | ``VRELOCABLE`` object include | set. |
| | ``OP_CLOSURE`` ``OP_NEWTABLE`` | |
| | ``OP_GETUPVAL`` ``OP_GETTABUP`` | |
| | ``OP_GETTABLE`` ``OP_NOT`` and code | |
| | for binary and unary expressions that | |
| | produce values (arithmetic operations, | |
| | bitwise operations, concat, length). | |
| | The associated code instruction has | |
| | operand ``A`` unset (defaulted to 0) - | |
| | this the ``VRELOCABLE`` expression | |
| | must be later transitioned to | |
| | ``VNONRELOC`` state when the register | |
| | is set. | |
+------------------+----------------------------------------+------------------------------------+
|``VNONRELOC`` | This state indicates that the output | As for transitions, the |
| | or result register has been set. The | ``VNONELOC`` state results from |
| | register is referenced in ``u.info`` | ``VRELOCABLE`` after a register |
| | parameter. Once set the register cannot| is assigned to the operation |
| | be changed for this expression - | referenced by ``VRELOCABLE``. |
| | subsequent operations involving this | Also a ``VCALL`` expression |
| | expression can refer to the register | transitions to ``VNONRELOC`` |
| | to obtain the result value. | expression - ``u.info`` is set to |
| | | the operand ``A`` of the associated|
| | | call instruction. ``VLOCAL`` |
| | | ``VNIL`` ``VTRUE`` ``VFALSE`` |
| | | ``VK`` ``VKINT`` ``VKFLT`` and |
| | | ``VJMP`` expressions transition to |
| | | ``VNONRELOC``. |
+------------------+----------------------------------------+------------------------------------+
|``VLOCAL`` | This is used when referencing local | The ``VLOCAL`` expression may |
| | variables. ``u.info`` is set to the | transition to ``VNONRELOC`` |
| | local variable's register. | although this doesn't change the |
| | | ``u.info`` parameter. |
+------------------+----------------------------------------+------------------------------------+
|``VCALL`` | This results from a function call. The | In terms of transitions, the |
| | ``OP_CALL`` instruction is referenced | ``VCALL`` expression transitions to|
| | by ``u.info`` parameter and may be | ``VNONRELOC`` When this happens |
| | retrieved by calling | the result register in |
| | ``getcode(FuncState *, expdesc *)``. | ``VNONRELOC`` (``u.info`` is set |
| | The ``OP_CALL`` instruction gets | to the operand ``A`` in the |
| | changed to ``OP_TAILCALL`` if the | ``OP_CALL`` instruction. |
| | function call expression is the value | |
| | of a ``RETURN`` statement. | |
| | The instructions operand ``C`` | |
| | gets updated when it is known the | |
| | number of expected results from the | |
| | function call. | |
+------------------+----------------------------------------+------------------------------------+
|``VINDEXED`` | This expression represents a table | The ``VINDEXED`` expression |
| | access. The ``u.ind.t`` parameter is | transitions to ``VRELOCABLE`` |
| | set to the register or upvalue? that |When this happens the ``u.info`` |
| | holds the table, the ``u.ind.idx`` is | is set to the offset of the code |
| | set to the register or constant that | that contains the opcode |
| | is the key, and ``u.ind.vt`` is either |``OP_GETTABUP`` if ``u.ind.vt`` was |
| |``VLOCAL`` or ``VUPVAL`` | ``VUPVAL`` or ``OP_GETTABLE`` if |
| | | ``u.ind.vt`` was ``VLOCAL`` |
+------------------+----------------------------------------+------------------------------------+

Examples of Parsing
-------------------
Expand Down

0 comments on commit 125e084

Please sign in to comment.