1 /* GDB-specific functions for operating on agent expressions 2 Copyright (C) 1998-2023 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 #include "ax.h" /* For agent_expr_up. */ 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 /* If nonzero, this is a variable which does not actually exist in 86 the program. */ 87 char optimized_out; 88 89 union 90 { 91 /* if kind == axs_lvalue_register, this is the register number */ 92 int reg; 93 } 94 u; 95 }; 96 97 98 /* Translating GDB expressions into agent expressions. */ 99 100 /* Given a GDB expression EXPR, return bytecode to trace its value. 101 The result will use the `trace' and `trace_quick' bytecodes to 102 record the value of all memory touched by the expression, and leave 103 no values on the stack. The caller can then use the ax_reqs 104 function to discover which registers the expression uses. */ 105 extern agent_expr_up gen_trace_for_expr (CORE_ADDR, struct expression *, 106 int); 107 108 extern agent_expr_up gen_trace_for_var (CORE_ADDR, struct gdbarch *, 109 struct symbol *, int); 110 111 extern agent_expr_up gen_trace_for_return_address (CORE_ADDR, 112 struct gdbarch *, 113 int); 114 115 extern agent_expr_up gen_eval_for_expr (CORE_ADDR, struct expression *); 116 117 extern void gen_expr (struct expression *exp, union exp_element **pc, 118 struct agent_expr *ax, struct axs_value *value); 119 120 extern void require_rvalue (struct agent_expr *ax, struct axs_value *value); 121 122 extern agent_expr_up gen_printf (CORE_ADDR, struct gdbarch *, 123 CORE_ADDR, LONGEST, const char *, int, 124 int, struct expression **); 125 126 #endif /* AX_GDB_H */ 127