1 /* GDB-specific functions for operating on agent expressions 2 Copyright (C) 1998-2016 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 22 struct expression; 23 union exp_element; 24 25 /* Types and enums */ 26 27 /* GDB stores expressions in the form of a flattened tree (struct 28 expression), so we just walk that tree and generate agent bytecodes 29 as we go along. 30 31 GDB's normal evaluation uses struct value, which contains the 32 expression's value as well as its address or the register it came 33 from. The `+' operator uses the value, whereas the unary `&' 34 operator will use the address portion. The `=' operator will use 35 the address or register number of its left hand side. 36 37 The issues are different when generating agent bytecode. Given a 38 variable reference expression, we should not necessarily generate 39 code to fetch its value, because the next operator may be `=' or 40 unary `&'. Instead, when we recurse on a subexpression, we 41 indicate whether we want that expression to produce an lvalue or an 42 rvalue. If we requested an lvalue, then the recursive call tells 43 us whether it generated code to compute an address on the stack, or 44 whether the lvalue lives in a register. 45 46 The `axs' prefix here means `agent expression, static', because 47 this is all static analysis of the expression, i.e. analysis which 48 doesn't depend on the contents of memory and registers. */ 49 50 51 /* Different kinds of agent expression static values. */ 52 enum axs_lvalue_kind 53 { 54 /* We generated code to compute the subexpression's value. 55 Constants and arithmetic operators yield this. */ 56 axs_rvalue, 57 58 /* We generated code to yield the subexpression's value's address on 59 the top of the stack. If the caller needs an rvalue, it should 60 call require_rvalue to produce the rvalue from this address. */ 61 axs_lvalue_memory, 62 63 /* We didn't generate any code, and the stack is undisturbed, 64 because the subexpression's value lives in a register; u.reg is 65 the register number. If the caller needs an rvalue, it should 66 call require_rvalue to produce the rvalue from this register 67 number. */ 68 axs_lvalue_register 69 }; 70 71 /* Structure describing what we got from a subexpression. Think of 72 this as parallel to value.h's enum lval_type, except that we're 73 describing a value which will exist when the expression is 74 evaluated in the future, not a value we have in our hand. */ 75 struct axs_value 76 { 77 enum axs_lvalue_kind kind; /* see above */ 78 79 /* The type of the subexpression. Even if lvalue == axs_lvalue_memory, 80 this is the type of the value itself; the value on the stack is a 81 "pointer to" an object of this type. */ 82 struct type *type; 83 84 /* If nonzero, this is a variable which does not actually exist in 85 the program. */ 86 char optimized_out; 87 88 union 89 { 90 /* if kind == axs_lvalue_register, this is the register number */ 91 int reg; 92 } 93 u; 94 }; 95 96 97 /* Translating GDB expressions into agent expressions. */ 98 99 /* Given a GDB expression EXPR, return bytecode to trace its value. 100 The result will use the `trace' and `trace_quick' bytecodes to 101 record the value of all memory touched by the expression, and leave 102 no values on the stack. The caller can then use the ax_reqs 103 function to discover which registers the expression uses. */ 104 extern struct agent_expr *gen_trace_for_expr (CORE_ADDR, struct expression *, 105 int); 106 107 extern struct agent_expr *gen_trace_for_var (CORE_ADDR, struct gdbarch *, 108 struct symbol *, int); 109 110 extern struct agent_expr *gen_trace_for_return_address (CORE_ADDR, 111 struct gdbarch *, 112 int); 113 114 extern struct agent_expr *gen_eval_for_expr (CORE_ADDR, struct expression *); 115 116 extern void gen_expr (struct expression *exp, union exp_element **pc, 117 struct agent_expr *ax, struct axs_value *value); 118 119 extern void require_rvalue (struct agent_expr *ax, struct axs_value *value); 120 121 struct format_piece; 122 extern struct agent_expr *gen_printf (CORE_ADDR, struct gdbarch *, 123 CORE_ADDR, LONGEST, const char *, int, 124 struct format_piece *, 125 int, struct expression **); 126 127 #endif /* AX_GDB_H */ 128