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jeremybenn |
/* 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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