1 /* GDB-specific functions for operating on agent expressions 2 Copyright 1998, 1999, 2000 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 2 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, write to the Free Software 18 Foundation, Inc., 59 Temple Place - Suite 330, 19 Boston, MA 02111-1307, USA. */ 20 21 #ifndef AX_GDB_H 22 #define AX_GDB_H 23 24 struct expression; 25 26 /* Types and enums */ 27 28 /* GDB stores expressions in the form of a flattened tree (struct 29 expression), so we just walk that tree and generate agent bytecodes 30 as we go along. 31 32 GDB's normal evaluation uses struct value, which contains the 33 expression's value as well as its address or the register it came 34 from. The `+' operator uses the value, whereas the unary `&' 35 operator will use the address portion. The `=' operator will use 36 the address or register number of its left hand side. 37 38 The issues are different when generating agent bytecode. Given a 39 variable reference expression, we should not necessarily generate 40 code to fetch its value, because the next operator may be `=' or 41 unary `&'. Instead, when we recurse on a subexpression, we 42 indicate whether we want that expression to produce an lvalue or an 43 rvalue. If we requested an lvalue, then the recursive call tells 44 us whether it generated code to compute an address on the stack, or 45 whether the lvalue lives in a register. 46 47 The `axs' prefix here means `agent expression, static', because 48 this is all static analysis of the expression, i.e. analysis which 49 doesn't depend on the contents of memory and registers. */ 50 51 52 /* Different kinds of agent expression static values. */ 53 enum axs_lvalue_kind 54 { 55 /* We generated code to compute the subexpression's value. 56 Constants and arithmetic operators yield this. */ 57 axs_rvalue, 58 59 /* We generated code to yield the subexpression's value's address on 60 the top of the stack. If the caller needs an rvalue, it should 61 call require_rvalue to produce the rvalue from this address. */ 62 axs_lvalue_memory, 63 64 /* We didn't generate any code, and the stack is undisturbed, 65 because the subexpression's value lives in a register; u.reg is 66 the register number. If the caller needs an rvalue, it should 67 call require_rvalue to produce the rvalue from this register 68 number. */ 69 axs_lvalue_register 70 }; 71 72 /* Structure describing what we got from a subexpression. Think of 73 this as parallel to value.h's enum lval_type, except that we're 74 describing a value which will exist when the expression is 75 evaluated in the future, not a value we have in our hand. */ 76 struct axs_value 77 { 78 enum axs_lvalue_kind kind; /* see above */ 79 80 /* The type of the subexpression. Even if lvalue == axs_lvalue_memory, 81 this is the type of the value itself; the value on the stack is a 82 "pointer to" an object of this type. */ 83 struct type *type; 84 85 union 86 { 87 /* if kind == axs_lvalue_register, this is the register number */ 88 int reg; 89 } 90 u; 91 }; 92 93 94 /* Translating GDB expressions into agent expressions. */ 95 96 /* Given a GDB expression EXPR, translate it into the agent bytecode, 97 and return it. FLAGS are from enum expr_to_agent_flags. */ 98 extern struct agent_expr *expr_to_agent (struct expression *EXPR, 99 struct axs_value *VALUE); 100 101 /* Given a GDB expression EXPR denoting an lvalue in memory, produce a 102 string of agent bytecode which will leave its address and size on 103 the top of stack. Return the agent expression. */ 104 extern struct agent_expr *expr_to_address_and_size (struct expression *EXPR); 105 106 /* Given a GDB expression EXPR, return bytecode to trace its value. 107 The result will use the `trace' and `trace_quick' bytecodes to 108 record the value of all memory touched by the expression, and leave 109 no values on the stack. The caller can then use the ax_reqs 110 function to discover which registers the expression uses. */ 111 extern struct agent_expr *gen_trace_for_expr (CORE_ADDR, struct expression *); 112 113 #endif /* AX_GDB_H */ 114