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[/] [openrisc/] [trunk/] [gnu-old/] [gdb-6.8/] [gdb/] [ax-gdb.h] - Blame information for rev 840

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/* GDB-specific functions for operating on agent expressions
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   Copyright (C) 1998, 1999, 2000, 2007, 2008 Free Software Foundation, Inc.
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   This file is part of GDB.
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   This program is free software; you can redistribute it and/or modify
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   it under the terms of the GNU General Public License as published by
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   the Free Software Foundation; either version 3 of the License, or
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   (at your option) any later version.
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   This program is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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   GNU General Public License for more details.
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   You should have received a copy of the GNU General Public License
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   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
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#ifndef AX_GDB_H
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#define AX_GDB_H
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struct expression;
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/* Types and enums */
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/* GDB stores expressions in the form of a flattened tree (struct
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   expression), so we just walk that tree and generate agent bytecodes
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   as we go along.
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   GDB's normal evaluation uses struct value, which contains the
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   expression's value as well as its address or the register it came
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   from.  The `+' operator uses the value, whereas the unary `&'
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   operator will use the address portion.  The `=' operator will use
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   the address or register number of its left hand side.
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   The issues are different when generating agent bytecode.  Given a
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   variable reference expression, we should not necessarily generate
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   code to fetch its value, because the next operator may be `=' or
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   unary `&'.  Instead, when we recurse on a subexpression, we
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   indicate whether we want that expression to produce an lvalue or an
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   rvalue.  If we requested an lvalue, then the recursive call tells
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   us whether it generated code to compute an address on the stack, or
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   whether the lvalue lives in a register.
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   The `axs' prefix here means `agent expression, static', because
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   this is all static analysis of the expression, i.e. analysis which
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   doesn't depend on the contents of memory and registers.  */
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/* Different kinds of agent expression static values.  */
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enum axs_lvalue_kind
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  {
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    /* We generated code to compute the subexpression's value.
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       Constants and arithmetic operators yield this.  */
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    axs_rvalue,
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    /* We generated code to yield the subexpression's value's address on
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       the top of the stack.  If the caller needs an rvalue, it should
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       call require_rvalue to produce the rvalue from this address.  */
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    axs_lvalue_memory,
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    /* We didn't generate any code, and the stack is undisturbed,
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       because the subexpression's value lives in a register; u.reg is
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       the register number.  If the caller needs an rvalue, it should
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       call require_rvalue to produce the rvalue from this register
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       number.  */
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    axs_lvalue_register
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  };
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/* Structure describing what we got from a subexpression.  Think of
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   this as parallel to value.h's enum lval_type, except that we're
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   describing a value which will exist when the expression is
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   evaluated in the future, not a value we have in our hand.  */
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struct axs_value
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  {
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    enum axs_lvalue_kind kind;  /* see above */
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    /* The type of the subexpression.  Even if lvalue == axs_lvalue_memory,
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       this is the type of the value itself; the value on the stack is a
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       "pointer to" an object of this type. */
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    struct type *type;
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    union
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      {
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        /* if kind == axs_lvalue_register, this is the register number */
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        int reg;
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      }
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    u;
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  };
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/* Translating GDB expressions into agent expressions.  */
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/* Given a GDB expression EXPR, return bytecode to trace its value.
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   The result will use the `trace' and `trace_quick' bytecodes to
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   record the value of all memory touched by the expression, and leave
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   no values on the stack.  The caller can then use the ax_reqs
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   function to discover which registers the expression uses.  */
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extern struct agent_expr *gen_trace_for_expr (CORE_ADDR, struct expression *);
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#endif /* AX_GDB_H */

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