tct3base.h

/* $Header: d:/cvsroot/tads/tads3/TCT3BASE.H,v 1.3 1999/07/11 00:46:57 MJRoberts Exp $ */

/*
 *   Copyright (c) 1999, 2002 Michael J. Roberts.  All Rights Reserved.
 *
 *   Please see the accompanying license file, LICENSE.TXT, for information
 *   on using and copying this software.
 */
/*
Name
  tct3base.h - base parse node classes for T3 code generator
Function

Notes

Modified
  05/10/99 MJRoberts  - Creation
*/

#ifndef TCT3BASE_H
#define TCT3BASE_H

#include "tcprs.h"

/* include the target-independent base classes */
#include "tcpnbase.h"


/* ------------------------------------------------------------------------ */
/*
 *   Base parse node class
 */
class CTcPrsNode: public CTcPrsNodeBase
{
public:
    /*
     *   Generate code to assign into the expression as an lvalue.  By
     *   default, we'll throw an error; a default node should never be called
     *   upon to generate code as an assignment target, because the
     *   impossibility of this condition should be detected during parsing.
     *   Each class that overrides check_lvalue() to return true must
     *   override this to generate code for an assignment.
     *
     *   'typ' specifies the type of assignment - this specifies the
     *   assignment operator being generated.
     *
     *   'phase' indicates what part of the assignment we're generating.  For
     *   a simple assignment, this routine will be called only once, with
     *   phase set to 1.  For a compound assignment, this routine will be
     *   called twice.  The first call is phase 1. This can do one of two
     *   things:
     *
     *   - Generate the entire assignment code, and return TRUE to indicate
     *   that the assignment has been handled.  The caller will generate no
     *   more code.  This should be used when the particular combination of
     *   assignment type and lvalue can be specially optimized in the
     *   bytecode.
     *
     *   - Generate code to evaluate the lvalue's value, and prepare the
     *   stack for eventual assignment to the lvalue, and return FALSE.  The
     *   caller in this case will then generate generic code to combine the
     *   lvalue and rvalue.  For example, with operator '+=', the caller will
     *   generate the ADD instruction to compute 'lvalue + rvalue'.  The
     *   caller will finally call the routine again with phase set to 2.
     *
     *   During phase 2, the routine must generate code to assign the rvalue
     *   at top of stack to the lvalue.
     *
     *   Returns true if the assignment type was handled, false if not.
     *   Simple assignment must always be handled, but composite assignments
     *   (such as "+=" or "*=") can refused.  If the assignment isn't
     *   handled, the caller must perform a generic calculation to compute
     *   the result of the assignment (for example, for "+=", the caller must
     *   generate code compute the sum of the right-hand side and the
     *   original value of the left-hand side), then call gen_code_asi()
     *   again to generate a simple assignment.
     *
     *   In general, gen_code_asi() must generate code for complex
     *   assignments itself only when it can take advantage of special
     *   opcodes that would result in more efficient generated code.  When no
     *   special opcodes are available for the assignment, there's no need
     *   for special coding here.
     *
     *   If 'ignore_error' is true, this should not generate an error if this
     *   node is not a suitable lvalue, but should simply return false.
     *
     *   'explicit' is true if this is an explicit assignment by user code,
     *   false if it's an assignment generated automatically by the compiler.
     *   Implicit assignments don't count for the purposes of unused value
     *   warnings.  These warnings are primarily to alert the user that they
     *   could delete an unnecessary assignment from their code, or
     *   conversely that they might have forgotten to do something with the
     *   value that the assignment would suggest they intended to do, but
     *   with a compiler-generated assignment there's nothing for the user to
     *   delete to fix the warning.
     *
     *   'ctx' is the address of a 'void *' variable (a generic pointer).
     *   This is for the callee's use during a two-phase compound operator
     *   assignment, for passing itself context information between the
     *   phases.  On phase 1, the callee can allocate a structure and store
     *   it at *ctx.  On phase 2, the callee can then look at this structure
     *   to retrieve information saved from the first phase.  The callee is
     *   responsible for deleting the structure on the second phase.  For
     *   single-phase TC_ASI_SIMPLE calls, the caller can simply pass a null
     *   pointer for ctx, so the callee must not attempt to store anything
     *   here during a simple assignment call.
     */
    virtual int gen_code_asi(int discard, int phase,
                             tc_asitype_t typ, const char *op,
                             class CTcPrsNode *rhs,
                             int ignore_error, int xplicit, void **ctx);

    /*
     *   Generate code to take the address of the expression.  By default,
     *   we'll throw an internal error; a default node should never be
     *   called upon to generate code to take its address, because we
     *   shouldn't be able to parse such a thing.  Each class that
     *   overrides has_addr() to return true must override this to
     *   generate address code.
     */
    virtual void gen_code_addr();

    /*
     *   Generate an if-then-else condition test.  This is called on the
     *   controlling expression of an if-then-else, and can also be called on
     *   subexpressions of short-circuit operators (|| and &&).  The purpose
     *   of this type of code generation is to avoid pushing the result of
     *   the controlling expression onto the stack when this can be avoided,
     *   and generate a jump to the appropriate if-else branch directly.
     *
     *   Either then_label or else_label will be non-null; the one that's
     *   null directly follows the condition test, so we are simply to fall
     *   through to that code rather than jump to it explicitly.
     */
    virtual void gen_code_cond(struct CTcCodeLabel *then_label,
                               struct CTcCodeLabel *else_label);

    /*
     *   Generate code to call the expression as a function or method.
     *   The caller will already have generated code to push the argument
     *   list; this routine only needs to generate code to make the call.
     *
     *   By default, we'll assume that the result of evaluating the
     *   expression is a method or function pointer, so we'll generate a
     *   call-indirect instruction to call the result of evaluating the
     *   expression.
     */
    virtual void gen_code_call(int discard, int argc, int varargs,
                               struct CTcNamedArgs *named_args);

    /*
     *   Generate code to apply operator 'new' to the expression.  By
     *   default, 'new' cannot be applied to an expression; nodes that
     *   allow operator 'new' must override this.
     */
    virtual void gen_code_new(int discard, int argc,
                              int varargs, struct CTcNamedArgs *named_args,
                              int from_call, int is_transient);

    /*
     *   Generate code to evaluate a member expression on this object
     *   expression, calling the property expression given.  By default,
     *   we'll evaluate our own expression to yield the object value, then
     *   get the property expression (either as a constant or by
     *   generating code to yield a property pointer), then we'll invoke
     *   that code.  Nodes should override this where more specific
     *   instructions can be generated.
     *
     *   If 'prop_is_expr' is true, the property expression (prop_expr) is
     *   a parenthesized expression; otherwise, it's a simple property
     *   symbol.  (We need this information because a symbol enclosed in
     *   parentheses would be otherwise indistinguishable from a plain
     *   symbol, but the two syntax cases differ in their behavior: a
     *   plain symbol is always a property name, whereas a symbol in
     *   parentheses can be a local variable.)
     */
    virtual void gen_code_member(int discard,
                                 class CTcPrsNode *prop_expr,
                                 int prop_is_expr,
                                 int argc, int varargs,
                                 struct CTcNamedArgs *named_args);

    /*
     *   Generate code for an object on the left side of a '.' expression.
     *   If possible, return the constant object rather than generating
     *   code.  If the expression refers to "self", set (*is_self) to true
     *   and return VM_INVALID_OBJ; otherwise, if the expression refers to
     *   a constant object reference, set (*is_self) to false and return
     *   the constant object value; otherwise, generate code for the
     *   expression, set (*is_self) to false, and return VM_INVALID_OBJ to
     *   indicate that the value must be obtained from the generated code
     *   at run-time.
     *
     *   By default, we'll use generated code to get the value.
     */
    virtual vm_obj_id_t gen_code_obj_predot(int *is_self)
    {
        /* generate the expression */
        gen_code(FALSE, FALSE);

        /* tell the caller that the value is not a compile-time constant */
        *is_self = FALSE;
        return VM_INVALID_OBJ;
    }


    /*
     *   generic generation for a member expression after the left side
     *   has been generated
     */
    static void s_gen_member_rhs(int discard,
                                 class CTcPrsNode *prop_expr,
                                 int prop_is_expr,
                                 int argc, int varargs,
                                 struct CTcNamedArgs *named_args);

    /*
     *   Get the property ID of this expression.  If the property ID is
     *   available as a constant value, this doesn't generate any code and
     *   simply returns the constant property ID value.  If this
     *   expression requires run-time evaluation, we'll generate code for
     *   the expression and return VM_INVALID_PROP to indicate that a
     *   constant property ID is not available.
     *
     *   If 'check_only' is true, this routine should only check to see
     *   whether a constant property value is available and return the
     *   appropriate indication, but should not generate any code in any
     *   case.  Errors should also be suppressed in this case, because the
     *   routine will always be called again to perform the actual
     *   generation, at which point any errors can be logged.
     *
     *   If 'is_expr' is true, it means that this property was given as an
     *   expression by being explicitly enclosed in parentheses.  If
     *   'is_expr' is false, it means that the property was given as a
     *   simple symbol name.  For cases where the property expression is a
     *   symbol, this distinction is important because we must resolve an
     *   unparenthesized symbol as a property name, even if it's hidden by
     *   a local variable.
     */
    virtual vm_prop_id_t gen_code_propid(int check_only, int is_expr);

    /*
     *   generate a jump-ahead instruction, returning a new label which
     *   serves as the jump destination
     */
    static struct CTcCodeLabel *gen_jump_ahead(uchar opc);

    /* define the position of a code label */
    static void def_label_pos(struct CTcCodeLabel *lbl);

    /* allocate a new label at the current write position */
    static struct CTcCodeLabel *new_label_here();
};

/* ------------------------------------------------------------------------ */
/*
 *   Basic T3-specific symbol class
 */
class CTcSymbol: public CTcSymbolBase
{
public:
    CTcSymbol(const char *str, size_t len, int copy, tc_symtype_t typ)
        : CTcSymbolBase(str, len, copy, typ) { }

    /*
     *   get the object value for the symbol, if the symbol has an object
     *   value; returns VM_INVALID_OBJ if the symbol is not an object
     */
    virtual vm_obj_id_t get_val_obj() const { return VM_INVALID_OBJ; }

    /* generate code to evaluate the symbol */
    virtual void gen_code(int discard) = 0;

    /*
     *   Generate code to assign to the symbol.  By default, we'll generate
     *   an error indicating that the symbol cannot be assigned into.  As
     *   with CTcPrsNode::gen_code_asi(), this returns true if the assignment
     *   was generated, false if the caller must generate a generic
     *   assignment; simple assignment must always return true.
     *
     *   If 'rhs' is null, the caller has already generated the value to be
     *   assigned, so this code doesn't need to do that.  Otherwise, this
     *   code must generate the rvalue code.  The reason that 'rhs' is passed
     *   down at all is that we can sometimes optimize the type of opcode we
     *   generate according to the type of value being assigned, especially
     *   when a constant value is being assigned.
     *
     *   If 'ignore_error' is true, this should not log an error if the value
     *   cannot be assigned.
     *
     *   'xplicit' is true if this is an explicit assignment by user code,
     *   false if it's an assignment generated automatically by the compiler.
     *   Implicit assignments don't count for the purposes of unused value
     *   warnings.  These warnings are primarily to alert the user that they
     *   could delete an unnecessary assignment from their code, or
     *   conversely that they might have forgotten to do something with the
     *   value that the assignment would suggest they intended to do, but
     *   with a compiler-generated assignment there's nothing for the user to
     *   delete to fix the warning.
     */
    virtual int gen_code_asi(int discard, int phase,
                             tc_asitype_t typ, const char *op,
                             class CTcPrsNode *rhs,
                             int ignore_error, int xplicit, void **ctx);

    /*
     *   Generate code for taking the address of the symbol.  By default,
     *   we'll generate an error indicating that the symbol's address
     *   cannot be taken.
     */
    virtual void gen_code_addr();

    /*
     *   Generate code to call the symbol.  By default, we can't call a
     *   symbol.
     */
    virtual void gen_code_call(int discard, int argc, int varargs,
                               struct CTcNamedArgs *named_args);

    /*
     *   generate code for operator 'new' applied to the symbol, with the
     *   given number of arguments; by default, we can't generate any such
     *   code
     */
    virtual void gen_code_new(int discard, int argc,
                              int varargs, struct CTcNamedArgs *named_args,
                              int is_transient);

    /* evaluate a property ID */
    virtual vm_prop_id_t gen_code_propid(int check_only, int is_expr);

    /* generate code for a member expression */
    virtual void gen_code_member(int discard,
                                 class CTcPrsNode *prop_expr,
                                 int prop_is_expr,
                                 int argc, int varargs,
                                 struct CTcNamedArgs *named_args);

    /* get the object value for a '.' expression */
    virtual vm_obj_id_t gen_code_obj_predot(int *is_self);

    /*
     *   Write the symbol to a local frame debugging record in the code
     *   stream.  Returns true if we wrote the symbol, false if not.  By
     *   default, we'll write nothing and return false, since most symbols
     *   aren't used in local symbol tables.
     */
    virtual int write_to_debug_frame(int test_only) { return FALSE; }

    /*
     *   Write the symbol to the global symbol table in the debugging
     *   records in an image file.  Returns true if we wrote the symbol,
     *   false if not.  By default, we'll write nothing and return false,
     *   since by default symbols don't go in the image file's global
     *   symbol table.
     */
    virtual int write_to_image_file_global(class CVmImageWriter *)
        { return FALSE; }
};

#endif /* TCT3BASE_H */