1/* GDB-specific functions for operating on agent expressions 2 Copyright (C) 1998, 1999, 2000, 2007 Free Software Foundation, Inc. 3 4 This file is part of GDB. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 18 19#ifndef AX_GDB_H 20#define AX_GDB_H 21 22struct expression; 23 24/* Types and enums */ 25 26/* GDB stores expressions in the form of a flattened tree (struct 27 expression), so we just walk that tree and generate agent bytecodes 28 as we go along. 29 30 GDB's normal evaluation uses struct value, which contains the 31 expression's value as well as its address or the register it came 32 from. The `+' operator uses the value, whereas the unary `&' 33 operator will use the address portion. The `=' operator will use 34 the address or register number of its left hand side. 35 36 The issues are different when generating agent bytecode. Given a 37 variable reference expression, we should not necessarily generate 38 code to fetch its value, because the next operator may be `=' or 39 unary `&'. Instead, when we recurse on a subexpression, we 40 indicate whether we want that expression to produce an lvalue or an 41 rvalue. If we requested an lvalue, then the recursive call tells 42 us whether it generated code to compute an address on the stack, or 43 whether the lvalue lives in a register. 44 45 The `axs' prefix here means `agent expression, static', because 46 this is all static analysis of the expression, i.e. analysis which 47 doesn't depend on the contents of memory and registers. */ 48 49 50/* Different kinds of agent expression static values. */ 51enum axs_lvalue_kind 52 { 53 /* We generated code to compute the subexpression's value. 54 Constants and arithmetic operators yield this. */ 55 axs_rvalue, 56 57 /* We generated code to yield the subexpression's value's address on 58 the top of the stack. If the caller needs an rvalue, it should 59 call require_rvalue to produce the rvalue from this address. */ 60 axs_lvalue_memory, 61 62 /* We didn't generate any code, and the stack is undisturbed, 63 because the subexpression's value lives in a register; u.reg is 64 the register number. If the caller needs an rvalue, it should 65 call require_rvalue to produce the rvalue from this register 66 number. */ 67 axs_lvalue_register 68 }; 69 70/* Structure describing what we got from a subexpression. Think of 71 this as parallel to value.h's enum lval_type, except that we're 72 describing a value which will exist when the expression is 73 evaluated in the future, not a value we have in our hand. */ 74struct axs_value 75 { 76 enum axs_lvalue_kind kind; /* see above */ 77 78 /* The type of the subexpression. Even if lvalue == axs_lvalue_memory, 79 this is the type of the value itself; the value on the stack is a 80 "pointer to" an object of this type. */ 81 struct type *type; 82 83 union 84 { 85 /* if kind == axs_lvalue_register, this is the register number */ 86 int reg; 87 } 88 u; 89 }; 90 91 92/* Translating GDB expressions into agent expressions. */ 93 94/* Given a GDB expression EXPR, translate it into the agent bytecode, 95 and return it. FLAGS are from enum expr_to_agent_flags. */ 96extern struct agent_expr *expr_to_agent (struct expression *EXPR, 97 struct axs_value *VALUE); 98 99/* Given a GDB expression EXPR denoting an lvalue in memory, produce a 100 string of agent bytecode which will leave its address and size on 101 the top of stack. Return the agent expression. */ 102extern struct agent_expr *expr_to_address_and_size (struct expression *EXPR); 103 104/* Given a GDB expression EXPR, return bytecode to trace its value. 105 The result will use the `trace' and `trace_quick' bytecodes to 106 record the value of all memory touched by the expression, and leave 107 no values on the stack. The caller can then use the ax_reqs 108 function to discover which registers the expression uses. */ 109extern struct agent_expr *gen_trace_for_expr (CORE_ADDR, struct expression *); 110 111#endif /* AX_GDB_H */ 112