1 /* GDB-specific functions for operating on agent expressions.
3 Copyright 1998, 1999, 2000, 2001, 2003 Free Software Foundation,
6 This file is part of GDB.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 59 Temple Place - Suite 330,
21 Boston, MA 02111-1307, USA. */
28 #include "expression.h"
35 #include "gdb_string.h"
38 /* To make sense of this file, you should read doc/agentexpr.texi.
39 Then look at the types and enums in ax-gdb.h. For the code itself,
40 look at gen_expr, towards the bottom; that's the main function that
41 looks at the GDB expressions and calls everything else to generate
44 I'm beginning to wonder whether it wouldn't be nicer to internally
45 generate trees, with types, and then spit out the bytecode in
46 linear form afterwards; we could generate fewer `swap', `ext', and
47 `zero_ext' bytecodes that way; it would make good constant folding
48 easier, too. But at the moment, I think we should be willing to
49 pay for the simplicity of this code with less-than-optimal bytecode
52 Remember, "GBD" stands for "Great Britain, Dammit!" So be careful. */
56 /* Prototypes for local functions. */
58 /* There's a standard order to the arguments of these functions:
59 union exp_element ** --- pointer into expression
60 struct agent_expr * --- agent expression buffer to generate code into
61 struct axs_value * --- describes value left on top of stack */
63 static struct value
*const_var_ref (struct symbol
*var
);
64 static struct value
*const_expr (union exp_element
**pc
);
65 static struct value
*maybe_const_expr (union exp_element
**pc
);
67 static void gen_traced_pop (struct agent_expr
*, struct axs_value
*);
69 static void gen_sign_extend (struct agent_expr
*, struct type
*);
70 static void gen_extend (struct agent_expr
*, struct type
*);
71 static void gen_fetch (struct agent_expr
*, struct type
*);
72 static void gen_left_shift (struct agent_expr
*, int);
75 static void gen_frame_args_address (struct agent_expr
*);
76 static void gen_frame_locals_address (struct agent_expr
*);
77 static void gen_offset (struct agent_expr
*ax
, int offset
);
78 static void gen_sym_offset (struct agent_expr
*, struct symbol
*);
79 static void gen_var_ref (struct agent_expr
*ax
,
80 struct axs_value
*value
, struct symbol
*var
);
83 static void gen_int_literal (struct agent_expr
*ax
,
84 struct axs_value
*value
,
85 LONGEST k
, struct type
*type
);
88 static void require_rvalue (struct agent_expr
*ax
, struct axs_value
*value
);
89 static void gen_usual_unary (struct agent_expr
*ax
, struct axs_value
*value
);
90 static int type_wider_than (struct type
*type1
, struct type
*type2
);
91 static struct type
*max_type (struct type
*type1
, struct type
*type2
);
92 static void gen_conversion (struct agent_expr
*ax
,
93 struct type
*from
, struct type
*to
);
94 static int is_nontrivial_conversion (struct type
*from
, struct type
*to
);
95 static void gen_usual_arithmetic (struct agent_expr
*ax
,
96 struct axs_value
*value1
,
97 struct axs_value
*value2
);
98 static void gen_integral_promotions (struct agent_expr
*ax
,
99 struct axs_value
*value
);
100 static void gen_cast (struct agent_expr
*ax
,
101 struct axs_value
*value
, struct type
*type
);
102 static void gen_scale (struct agent_expr
*ax
,
103 enum agent_op op
, struct type
*type
);
104 static void gen_add (struct agent_expr
*ax
,
105 struct axs_value
*value
,
106 struct axs_value
*value1
,
107 struct axs_value
*value2
, char *name
);
108 static void gen_sub (struct agent_expr
*ax
,
109 struct axs_value
*value
,
110 struct axs_value
*value1
, struct axs_value
*value2
);
111 static void gen_binop (struct agent_expr
*ax
,
112 struct axs_value
*value
,
113 struct axs_value
*value1
,
114 struct axs_value
*value2
,
116 enum agent_op op_unsigned
, int may_carry
, char *name
);
117 static void gen_logical_not (struct agent_expr
*ax
, struct axs_value
*value
);
118 static void gen_complement (struct agent_expr
*ax
, struct axs_value
*value
);
119 static void gen_deref (struct agent_expr
*, struct axs_value
*);
120 static void gen_address_of (struct agent_expr
*, struct axs_value
*);
121 static int find_field (struct type
*type
, char *name
);
122 static void gen_bitfield_ref (struct agent_expr
*ax
,
123 struct axs_value
*value
,
124 struct type
*type
, int start
, int end
);
125 static void gen_struct_ref (struct agent_expr
*ax
,
126 struct axs_value
*value
,
128 char *operator_name
, char *operand_name
);
129 static void gen_repeat (union exp_element
**pc
,
130 struct agent_expr
*ax
, struct axs_value
*value
);
131 static void gen_sizeof (union exp_element
**pc
,
132 struct agent_expr
*ax
, struct axs_value
*value
);
133 static void gen_expr (union exp_element
**pc
,
134 struct agent_expr
*ax
, struct axs_value
*value
);
136 static void print_axs_value (struct ui_file
*f
, struct axs_value
* value
);
137 static void agent_command (char *exp
, int from_tty
);
140 /* Detecting constant expressions. */
142 /* If the variable reference at *PC is a constant, return its value.
143 Otherwise, return zero.
145 Hey, Wally! How can a variable reference be a constant?
147 Well, Beav, this function really handles the OP_VAR_VALUE operator,
148 not specifically variable references. GDB uses OP_VAR_VALUE to
149 refer to any kind of symbolic reference: function names, enum
150 elements, and goto labels are all handled through the OP_VAR_VALUE
151 operator, even though they're constants. It makes sense given the
154 Gee, Wally, don'cha wonder sometimes if data representations that
155 subvert commonly accepted definitions of terms in favor of heavily
156 context-specific interpretations are really just a tool of the
157 programming hegemony to preserve their power and exclude the
160 static struct value
*
161 const_var_ref (struct symbol
*var
)
163 struct type
*type
= SYMBOL_TYPE (var
);
165 switch (SYMBOL_CLASS (var
))
168 return value_from_longest (type
, (LONGEST
) SYMBOL_VALUE (var
));
171 return value_from_pointer (type
, (CORE_ADDR
) SYMBOL_VALUE_ADDRESS (var
));
179 /* If the expression starting at *PC has a constant value, return it.
180 Otherwise, return zero. If we return a value, then *PC will be
181 advanced to the end of it. If we return zero, *PC could be
183 static struct value
*
184 const_expr (union exp_element
**pc
)
186 enum exp_opcode op
= (*pc
)->opcode
;
193 struct type
*type
= (*pc
)[1].type
;
194 LONGEST k
= (*pc
)[2].longconst
;
196 return value_from_longest (type
, k
);
201 struct value
*v
= const_var_ref ((*pc
)[2].symbol
);
206 /* We could add more operators in here. */
210 v1
= const_expr (pc
);
212 return value_neg (v1
);
222 /* Like const_expr, but guarantee also that *PC is undisturbed if the
223 expression is not constant. */
224 static struct value
*
225 maybe_const_expr (union exp_element
**pc
)
227 union exp_element
*tentative_pc
= *pc
;
228 struct value
*v
= const_expr (&tentative_pc
);
230 /* If we got a value, then update the real PC. */
238 /* Generating bytecode from GDB expressions: general assumptions */
240 /* Here are a few general assumptions made throughout the code; if you
241 want to make a change that contradicts one of these, then you'd
242 better scan things pretty thoroughly.
244 - We assume that all values occupy one stack element. For example,
245 sometimes we'll swap to get at the left argument to a binary
246 operator. If we decide that void values should occupy no stack
247 elements, or that synthetic arrays (whose size is determined at
248 run time, created by the `@' operator) should occupy two stack
249 elements (address and length), then this will cause trouble.
251 - We assume the stack elements are infinitely wide, and that we
252 don't have to worry what happens if the user requests an
253 operation that is wider than the actual interpreter's stack.
254 That is, it's up to the interpreter to handle directly all the
255 integer widths the user has access to. (Woe betide the language
258 - We don't support side effects. Thus, we don't have to worry about
259 GCC's generalized lvalues, function calls, etc.
261 - We don't support floating point. Many places where we switch on
262 some type don't bother to include cases for floating point; there
263 may be even more subtle ways this assumption exists. For
264 example, the arguments to % must be integers.
266 - We assume all subexpressions have a static, unchanging type. If
267 we tried to support convenience variables, this would be a
270 - All values on the stack should always be fully zero- or
273 (I wasn't sure whether to choose this or its opposite --- that
274 only addresses are assumed extended --- but it turns out that
275 neither convention completely eliminates spurious extend
276 operations (if everything is always extended, then you have to
277 extend after add, because it could overflow; if nothing is
278 extended, then you end up producing extends whenever you change
279 sizes), and this is simpler.) */
282 /* Generating bytecode from GDB expressions: the `trace' kludge */
284 /* The compiler in this file is a general-purpose mechanism for
285 translating GDB expressions into bytecode. One ought to be able to
286 find a million and one uses for it.
288 However, at the moment it is HOPELESSLY BRAIN-DAMAGED for the sake
289 of expediency. Let he who is without sin cast the first stone.
291 For the data tracing facility, we need to insert `trace' bytecodes
292 before each data fetch; this records all the memory that the
293 expression touches in the course of evaluation, so that memory will
294 be available when the user later tries to evaluate the expression
297 This should be done (I think) in a post-processing pass, that walks
298 an arbitrary agent expression and inserts `trace' operations at the
299 appropriate points. But it's much faster to just hack them
300 directly into the code. And since we're in a crunch, that's what
303 Setting the flag trace_kludge to non-zero enables the code that
304 emits the trace bytecodes at the appropriate points. */
305 static int trace_kludge
;
307 /* Trace the lvalue on the stack, if it needs it. In either case, pop
308 the value. Useful on the left side of a comma, and at the end of
309 an expression being used for tracing. */
311 gen_traced_pop (struct agent_expr
*ax
, struct axs_value
*value
)
317 /* We don't trace rvalues, just the lvalues necessary to
318 produce them. So just dispose of this value. */
319 ax_simple (ax
, aop_pop
);
322 case axs_lvalue_memory
:
324 int length
= TYPE_LENGTH (value
->type
);
326 /* There's no point in trying to use a trace_quick bytecode
327 here, since "trace_quick SIZE pop" is three bytes, whereas
328 "const8 SIZE trace" is also three bytes, does the same
329 thing, and the simplest code which generates that will also
330 work correctly for objects with large sizes. */
331 ax_const_l (ax
, length
);
332 ax_simple (ax
, aop_trace
);
336 case axs_lvalue_register
:
337 /* We need to mention the register somewhere in the bytecode,
338 so ax_reqs will pick it up and add it to the mask of
340 ax_reg (ax
, value
->u
.reg
);
341 ax_simple (ax
, aop_pop
);
345 /* If we're not tracing, just pop the value. */
346 ax_simple (ax
, aop_pop
);
351 /* Generating bytecode from GDB expressions: helper functions */
353 /* Assume that the lower bits of the top of the stack is a value of
354 type TYPE, and the upper bits are zero. Sign-extend if necessary. */
356 gen_sign_extend (struct agent_expr
*ax
, struct type
*type
)
358 /* Do we need to sign-extend this? */
359 if (!TYPE_UNSIGNED (type
))
360 ax_ext (ax
, TYPE_LENGTH (type
) * TARGET_CHAR_BIT
);
364 /* Assume the lower bits of the top of the stack hold a value of type
365 TYPE, and the upper bits are garbage. Sign-extend or truncate as
368 gen_extend (struct agent_expr
*ax
, struct type
*type
)
370 int bits
= TYPE_LENGTH (type
) * TARGET_CHAR_BIT
;
372 ((TYPE_UNSIGNED (type
) ? ax_zero_ext
: ax_ext
) (ax
, bits
));
376 /* Assume that the top of the stack contains a value of type "pointer
377 to TYPE"; generate code to fetch its value. Note that TYPE is the
378 target type, not the pointer type. */
380 gen_fetch (struct agent_expr
*ax
, struct type
*type
)
384 /* Record the area of memory we're about to fetch. */
385 ax_trace_quick (ax
, TYPE_LENGTH (type
));
388 switch (TYPE_CODE (type
))
394 /* It's a scalar value, so we know how to dereference it. How
395 many bytes long is it? */
396 switch (TYPE_LENGTH (type
))
398 case 8 / TARGET_CHAR_BIT
:
399 ax_simple (ax
, aop_ref8
);
401 case 16 / TARGET_CHAR_BIT
:
402 ax_simple (ax
, aop_ref16
);
404 case 32 / TARGET_CHAR_BIT
:
405 ax_simple (ax
, aop_ref32
);
407 case 64 / TARGET_CHAR_BIT
:
408 ax_simple (ax
, aop_ref64
);
411 /* Either our caller shouldn't have asked us to dereference
412 that pointer (other code's fault), or we're not
413 implementing something we should be (this code's fault).
414 In any case, it's a bug the user shouldn't see. */
416 internal_error (__FILE__
, __LINE__
,
417 "gen_fetch: strange size");
420 gen_sign_extend (ax
, type
);
424 /* Either our caller shouldn't have asked us to dereference that
425 pointer (other code's fault), or we're not implementing
426 something we should be (this code's fault). In any case,
427 it's a bug the user shouldn't see. */
428 internal_error (__FILE__
, __LINE__
,
429 "gen_fetch: bad type code");
434 /* Generate code to left shift the top of the stack by DISTANCE bits, or
435 right shift it by -DISTANCE bits if DISTANCE < 0. This generates
436 unsigned (logical) right shifts. */
438 gen_left_shift (struct agent_expr
*ax
, int distance
)
442 ax_const_l (ax
, distance
);
443 ax_simple (ax
, aop_lsh
);
445 else if (distance
< 0)
447 ax_const_l (ax
, -distance
);
448 ax_simple (ax
, aop_rsh_unsigned
);
454 /* Generating bytecode from GDB expressions: symbol references */
456 /* Generate code to push the base address of the argument portion of
457 the top stack frame. */
459 gen_frame_args_address (struct agent_expr
*ax
)
462 LONGEST frame_offset
;
464 TARGET_VIRTUAL_FRAME_POINTER (ax
->scope
, &frame_reg
, &frame_offset
);
465 ax_reg (ax
, frame_reg
);
466 gen_offset (ax
, frame_offset
);
470 /* Generate code to push the base address of the locals portion of the
473 gen_frame_locals_address (struct agent_expr
*ax
)
476 LONGEST frame_offset
;
478 TARGET_VIRTUAL_FRAME_POINTER (ax
->scope
, &frame_reg
, &frame_offset
);
479 ax_reg (ax
, frame_reg
);
480 gen_offset (ax
, frame_offset
);
484 /* Generate code to add OFFSET to the top of the stack. Try to
485 generate short and readable code. We use this for getting to
486 variables on the stack, and structure members. If we were
487 programming in ML, it would be clearer why these are the same
490 gen_offset (struct agent_expr
*ax
, int offset
)
492 /* It would suffice to simply push the offset and add it, but this
493 makes it easier to read positive and negative offsets in the
497 ax_const_l (ax
, offset
);
498 ax_simple (ax
, aop_add
);
502 ax_const_l (ax
, -offset
);
503 ax_simple (ax
, aop_sub
);
508 /* In many cases, a symbol's value is the offset from some other
509 address (stack frame, base register, etc.) Generate code to add
510 VAR's value to the top of the stack. */
512 gen_sym_offset (struct agent_expr
*ax
, struct symbol
*var
)
514 gen_offset (ax
, SYMBOL_VALUE (var
));
518 /* Generate code for a variable reference to AX. The variable is the
519 symbol VAR. Set VALUE to describe the result. */
522 gen_var_ref (struct agent_expr
*ax
, struct axs_value
*value
, struct symbol
*var
)
524 /* Dereference any typedefs. */
525 value
->type
= check_typedef (SYMBOL_TYPE (var
));
527 /* I'm imitating the code in read_var_value. */
528 switch (SYMBOL_CLASS (var
))
530 case LOC_CONST
: /* A constant, like an enum value. */
531 ax_const_l (ax
, (LONGEST
) SYMBOL_VALUE (var
));
532 value
->kind
= axs_rvalue
;
535 case LOC_LABEL
: /* A goto label, being used as a value. */
536 ax_const_l (ax
, (LONGEST
) SYMBOL_VALUE_ADDRESS (var
));
537 value
->kind
= axs_rvalue
;
540 case LOC_CONST_BYTES
:
541 internal_error (__FILE__
, __LINE__
,
542 "gen_var_ref: LOC_CONST_BYTES symbols are not supported");
544 /* Variable at a fixed location in memory. Easy. */
546 /* Push the address of the variable. */
547 ax_const_l (ax
, SYMBOL_VALUE_ADDRESS (var
));
548 value
->kind
= axs_lvalue_memory
;
551 case LOC_ARG
: /* var lives in argument area of frame */
552 gen_frame_args_address (ax
);
553 gen_sym_offset (ax
, var
);
554 value
->kind
= axs_lvalue_memory
;
557 case LOC_REF_ARG
: /* As above, but the frame slot really
558 holds the address of the variable. */
559 gen_frame_args_address (ax
);
560 gen_sym_offset (ax
, var
);
561 /* Don't assume any particular pointer size. */
562 gen_fetch (ax
, lookup_pointer_type (builtin_type_void
));
563 value
->kind
= axs_lvalue_memory
;
566 case LOC_LOCAL
: /* var lives in locals area of frame */
568 gen_frame_locals_address (ax
);
569 gen_sym_offset (ax
, var
);
570 value
->kind
= axs_lvalue_memory
;
573 case LOC_BASEREG
: /* relative to some base register */
574 case LOC_BASEREG_ARG
:
575 ax_reg (ax
, SYMBOL_BASEREG (var
));
576 gen_sym_offset (ax
, var
);
577 value
->kind
= axs_lvalue_memory
;
581 error ("Cannot compute value of typedef `%s'.",
582 SYMBOL_PRINT_NAME (var
));
586 ax_const_l (ax
, BLOCK_START (SYMBOL_BLOCK_VALUE (var
)));
587 value
->kind
= axs_rvalue
;
592 /* Don't generate any code at all; in the process of treating
593 this as an lvalue or rvalue, the caller will generate the
595 value
->kind
= axs_lvalue_register
;
596 value
->u
.reg
= SYMBOL_VALUE (var
);
599 /* A lot like LOC_REF_ARG, but the pointer lives directly in a
600 register, not on the stack. Simpler than LOC_REGISTER and
601 LOC_REGPARM, because it's just like any other case where the
602 thing has a real address. */
603 case LOC_REGPARM_ADDR
:
604 ax_reg (ax
, SYMBOL_VALUE (var
));
605 value
->kind
= axs_lvalue_memory
;
610 struct minimal_symbol
*msym
611 = lookup_minimal_symbol (DEPRECATED_SYMBOL_NAME (var
), NULL
, NULL
);
613 error ("Couldn't resolve symbol `%s'.", SYMBOL_PRINT_NAME (var
));
615 /* Push the address of the variable. */
616 ax_const_l (ax
, SYMBOL_VALUE_ADDRESS (msym
));
617 value
->kind
= axs_lvalue_memory
;
621 case LOC_OPTIMIZED_OUT
:
622 error ("The variable `%s' has been optimized out.",
623 SYMBOL_PRINT_NAME (var
));
627 error ("Cannot find value of botched symbol `%s'.",
628 SYMBOL_PRINT_NAME (var
));
635 /* Generating bytecode from GDB expressions: literals */
638 gen_int_literal (struct agent_expr
*ax
, struct axs_value
*value
, LONGEST k
,
642 value
->kind
= axs_rvalue
;
648 /* Generating bytecode from GDB expressions: unary conversions, casts */
650 /* Take what's on the top of the stack (as described by VALUE), and
651 try to make an rvalue out of it. Signal an error if we can't do
654 require_rvalue (struct agent_expr
*ax
, struct axs_value
*value
)
659 /* It's already an rvalue. */
662 case axs_lvalue_memory
:
663 /* The top of stack is the address of the object. Dereference. */
664 gen_fetch (ax
, value
->type
);
667 case axs_lvalue_register
:
668 /* There's nothing on the stack, but value->u.reg is the
669 register number containing the value.
671 When we add floating-point support, this is going to have to
672 change. What about SPARC register pairs, for example? */
673 ax_reg (ax
, value
->u
.reg
);
674 gen_extend (ax
, value
->type
);
678 value
->kind
= axs_rvalue
;
682 /* Assume the top of the stack is described by VALUE, and perform the
683 usual unary conversions. This is motivated by ANSI 6.2.2, but of
684 course GDB expressions are not ANSI; they're the mishmash union of
685 a bunch of languages. Rah.
687 NOTE! This function promises to produce an rvalue only when the
688 incoming value is of an appropriate type. In other words, the
689 consumer of the value this function produces may assume the value
690 is an rvalue only after checking its type.
692 The immediate issue is that if the user tries to use a structure or
693 union as an operand of, say, the `+' operator, we don't want to try
694 to convert that structure to an rvalue; require_rvalue will bomb on
695 structs and unions. Rather, we want to simply pass the struct
696 lvalue through unchanged, and let `+' raise an error. */
699 gen_usual_unary (struct agent_expr
*ax
, struct axs_value
*value
)
701 /* We don't have to generate any code for the usual integral
702 conversions, since values are always represented as full-width on
703 the stack. Should we tweak the type? */
705 /* Some types require special handling. */
706 switch (TYPE_CODE (value
->type
))
708 /* Functions get converted to a pointer to the function. */
710 value
->type
= lookup_pointer_type (value
->type
);
711 value
->kind
= axs_rvalue
; /* Should always be true, but just in case. */
714 /* Arrays get converted to a pointer to their first element, and
715 are no longer an lvalue. */
716 case TYPE_CODE_ARRAY
:
718 struct type
*elements
= TYPE_TARGET_TYPE (value
->type
);
719 value
->type
= lookup_pointer_type (elements
);
720 value
->kind
= axs_rvalue
;
721 /* We don't need to generate any code; the address of the array
722 is also the address of its first element. */
726 /* Don't try to convert structures and unions to rvalues. Let the
727 consumer signal an error. */
728 case TYPE_CODE_STRUCT
:
729 case TYPE_CODE_UNION
:
732 /* If the value is an enum, call it an integer. */
734 value
->type
= builtin_type_int
;
738 /* If the value is an lvalue, dereference it. */
739 require_rvalue (ax
, value
);
743 /* Return non-zero iff the type TYPE1 is considered "wider" than the
744 type TYPE2, according to the rules described in gen_usual_arithmetic. */
746 type_wider_than (struct type
*type1
, struct type
*type2
)
748 return (TYPE_LENGTH (type1
) > TYPE_LENGTH (type2
)
749 || (TYPE_LENGTH (type1
) == TYPE_LENGTH (type2
)
750 && TYPE_UNSIGNED (type1
)
751 && !TYPE_UNSIGNED (type2
)));
755 /* Return the "wider" of the two types TYPE1 and TYPE2. */
757 max_type (struct type
*type1
, struct type
*type2
)
759 return type_wider_than (type1
, type2
) ? type1
: type2
;
763 /* Generate code to convert a scalar value of type FROM to type TO. */
765 gen_conversion (struct agent_expr
*ax
, struct type
*from
, struct type
*to
)
767 /* Perhaps there is a more graceful way to state these rules. */
769 /* If we're converting to a narrower type, then we need to clear out
771 if (TYPE_LENGTH (to
) < TYPE_LENGTH (from
))
772 gen_extend (ax
, from
);
774 /* If the two values have equal width, but different signednesses,
775 then we need to extend. */
776 else if (TYPE_LENGTH (to
) == TYPE_LENGTH (from
))
778 if (TYPE_UNSIGNED (from
) != TYPE_UNSIGNED (to
))
782 /* If we're converting to a wider type, and becoming unsigned, then
783 we need to zero out any possible sign bits. */
784 else if (TYPE_LENGTH (to
) > TYPE_LENGTH (from
))
786 if (TYPE_UNSIGNED (to
))
792 /* Return non-zero iff the type FROM will require any bytecodes to be
793 emitted to be converted to the type TO. */
795 is_nontrivial_conversion (struct type
*from
, struct type
*to
)
797 struct agent_expr
*ax
= new_agent_expr (0);
800 /* Actually generate the code, and see if anything came out. At the
801 moment, it would be trivial to replicate the code in
802 gen_conversion here, but in the future, when we're supporting
803 floating point and the like, it may not be. Doing things this
804 way allows this function to be independent of the logic in
806 gen_conversion (ax
, from
, to
);
807 nontrivial
= ax
->len
> 0;
808 free_agent_expr (ax
);
813 /* Generate code to perform the "usual arithmetic conversions" (ANSI C
814 6.2.1.5) for the two operands of an arithmetic operator. This
815 effectively finds a "least upper bound" type for the two arguments,
816 and promotes each argument to that type. *VALUE1 and *VALUE2
817 describe the values as they are passed in, and as they are left. */
819 gen_usual_arithmetic (struct agent_expr
*ax
, struct axs_value
*value1
,
820 struct axs_value
*value2
)
822 /* Do the usual binary conversions. */
823 if (TYPE_CODE (value1
->type
) == TYPE_CODE_INT
824 && TYPE_CODE (value2
->type
) == TYPE_CODE_INT
)
826 /* The ANSI integral promotions seem to work this way: Order the
827 integer types by size, and then by signedness: an n-bit
828 unsigned type is considered "wider" than an n-bit signed
829 type. Promote to the "wider" of the two types, and always
830 promote at least to int. */
831 struct type
*target
= max_type (builtin_type_int
,
832 max_type (value1
->type
, value2
->type
));
834 /* Deal with value2, on the top of the stack. */
835 gen_conversion (ax
, value2
->type
, target
);
837 /* Deal with value1, not on the top of the stack. Don't
838 generate the `swap' instructions if we're not actually going
840 if (is_nontrivial_conversion (value1
->type
, target
))
842 ax_simple (ax
, aop_swap
);
843 gen_conversion (ax
, value1
->type
, target
);
844 ax_simple (ax
, aop_swap
);
847 value1
->type
= value2
->type
= target
;
852 /* Generate code to perform the integral promotions (ANSI 6.2.1.1) on
853 the value on the top of the stack, as described by VALUE. Assume
854 the value has integral type. */
856 gen_integral_promotions (struct agent_expr
*ax
, struct axs_value
*value
)
858 if (!type_wider_than (value
->type
, builtin_type_int
))
860 gen_conversion (ax
, value
->type
, builtin_type_int
);
861 value
->type
= builtin_type_int
;
863 else if (!type_wider_than (value
->type
, builtin_type_unsigned_int
))
865 gen_conversion (ax
, value
->type
, builtin_type_unsigned_int
);
866 value
->type
= builtin_type_unsigned_int
;
871 /* Generate code for a cast to TYPE. */
873 gen_cast (struct agent_expr
*ax
, struct axs_value
*value
, struct type
*type
)
875 /* GCC does allow casts to yield lvalues, so this should be fixed
876 before merging these changes into the trunk. */
877 require_rvalue (ax
, value
);
878 /* Dereference typedefs. */
879 type
= check_typedef (type
);
881 switch (TYPE_CODE (type
))
884 /* It's implementation-defined, and I'll bet this is what GCC
888 case TYPE_CODE_ARRAY
:
889 case TYPE_CODE_STRUCT
:
890 case TYPE_CODE_UNION
:
892 error ("Illegal type cast: intended type must be scalar.");
895 /* We don't have to worry about the size of the value, because
896 all our integral values are fully sign-extended, and when
897 casting pointers we can do anything we like. Is there any
898 way for us to actually know what GCC actually does with a
904 gen_conversion (ax
, value
->type
, type
);
908 /* We could pop the value, and rely on everyone else to check
909 the type and notice that this value doesn't occupy a stack
910 slot. But for now, leave the value on the stack, and
911 preserve the "value == stack element" assumption. */
915 error ("Casts to requested type are not yet implemented.");
923 /* Generating bytecode from GDB expressions: arithmetic */
925 /* Scale the integer on the top of the stack by the size of the target
926 of the pointer type TYPE. */
928 gen_scale (struct agent_expr
*ax
, enum agent_op op
, struct type
*type
)
930 struct type
*element
= TYPE_TARGET_TYPE (type
);
932 if (TYPE_LENGTH (element
) != 1)
934 ax_const_l (ax
, TYPE_LENGTH (element
));
940 /* Generate code for an addition; non-trivial because we deal with
941 pointer arithmetic. We set VALUE to describe the result value; we
942 assume VALUE1 and VALUE2 describe the two operands, and that
943 they've undergone the usual binary conversions. Used by both
944 BINOP_ADD and BINOP_SUBSCRIPT. NAME is used in error messages. */
946 gen_add (struct agent_expr
*ax
, struct axs_value
*value
,
947 struct axs_value
*value1
, struct axs_value
*value2
, char *name
)
950 if (TYPE_CODE (value1
->type
) == TYPE_CODE_INT
951 && TYPE_CODE (value2
->type
) == TYPE_CODE_PTR
)
953 /* Swap the values and proceed normally. */
954 ax_simple (ax
, aop_swap
);
955 gen_scale (ax
, aop_mul
, value2
->type
);
956 ax_simple (ax
, aop_add
);
957 gen_extend (ax
, value2
->type
); /* Catch overflow. */
958 value
->type
= value2
->type
;
962 else if (TYPE_CODE (value1
->type
) == TYPE_CODE_PTR
963 && TYPE_CODE (value2
->type
) == TYPE_CODE_INT
)
965 gen_scale (ax
, aop_mul
, value1
->type
);
966 ax_simple (ax
, aop_add
);
967 gen_extend (ax
, value1
->type
); /* Catch overflow. */
968 value
->type
= value1
->type
;
971 /* Must be number + number; the usual binary conversions will have
972 brought them both to the same width. */
973 else if (TYPE_CODE (value1
->type
) == TYPE_CODE_INT
974 && TYPE_CODE (value2
->type
) == TYPE_CODE_INT
)
976 ax_simple (ax
, aop_add
);
977 gen_extend (ax
, value1
->type
); /* Catch overflow. */
978 value
->type
= value1
->type
;
982 error ("Illegal combination of types in %s.", name
);
984 value
->kind
= axs_rvalue
;
988 /* Generate code for an addition; non-trivial because we have to deal
989 with pointer arithmetic. We set VALUE to describe the result
990 value; we assume VALUE1 and VALUE2 describe the two operands, and
991 that they've undergone the usual binary conversions. */
993 gen_sub (struct agent_expr
*ax
, struct axs_value
*value
,
994 struct axs_value
*value1
, struct axs_value
*value2
)
996 if (TYPE_CODE (value1
->type
) == TYPE_CODE_PTR
)
998 /* Is it PTR - INT? */
999 if (TYPE_CODE (value2
->type
) == TYPE_CODE_INT
)
1001 gen_scale (ax
, aop_mul
, value1
->type
);
1002 ax_simple (ax
, aop_sub
);
1003 gen_extend (ax
, value1
->type
); /* Catch overflow. */
1004 value
->type
= value1
->type
;
1007 /* Is it PTR - PTR? Strictly speaking, the types ought to
1008 match, but this is what the normal GDB expression evaluator
1010 else if (TYPE_CODE (value2
->type
) == TYPE_CODE_PTR
1011 && (TYPE_LENGTH (TYPE_TARGET_TYPE (value1
->type
))
1012 == TYPE_LENGTH (TYPE_TARGET_TYPE (value2
->type
))))
1014 ax_simple (ax
, aop_sub
);
1015 gen_scale (ax
, aop_div_unsigned
, value1
->type
);
1016 value
->type
= builtin_type_long
; /* FIXME --- should be ptrdiff_t */
1020 First argument of `-' is a pointer, but second argument is neither\n\
1021 an integer nor a pointer of the same type.");
1024 /* Must be number + number. */
1025 else if (TYPE_CODE (value1
->type
) == TYPE_CODE_INT
1026 && TYPE_CODE (value2
->type
) == TYPE_CODE_INT
)
1028 ax_simple (ax
, aop_sub
);
1029 gen_extend (ax
, value1
->type
); /* Catch overflow. */
1030 value
->type
= value1
->type
;
1034 error ("Illegal combination of types in subtraction.");
1036 value
->kind
= axs_rvalue
;
1039 /* Generate code for a binary operator that doesn't do pointer magic.
1040 We set VALUE to describe the result value; we assume VALUE1 and
1041 VALUE2 describe the two operands, and that they've undergone the
1042 usual binary conversions. MAY_CARRY should be non-zero iff the
1043 result needs to be extended. NAME is the English name of the
1044 operator, used in error messages */
1046 gen_binop (struct agent_expr
*ax
, struct axs_value
*value
,
1047 struct axs_value
*value1
, struct axs_value
*value2
, enum agent_op op
,
1048 enum agent_op op_unsigned
, int may_carry
, char *name
)
1050 /* We only handle INT op INT. */
1051 if ((TYPE_CODE (value1
->type
) != TYPE_CODE_INT
)
1052 || (TYPE_CODE (value2
->type
) != TYPE_CODE_INT
))
1053 error ("Illegal combination of types in %s.", name
);
1056 TYPE_UNSIGNED (value1
->type
) ? op_unsigned
: op
);
1058 gen_extend (ax
, value1
->type
); /* catch overflow */
1059 value
->type
= value1
->type
;
1060 value
->kind
= axs_rvalue
;
1065 gen_logical_not (struct agent_expr
*ax
, struct axs_value
*value
)
1067 if (TYPE_CODE (value
->type
) != TYPE_CODE_INT
1068 && TYPE_CODE (value
->type
) != TYPE_CODE_PTR
)
1069 error ("Illegal type of operand to `!'.");
1071 gen_usual_unary (ax
, value
);
1072 ax_simple (ax
, aop_log_not
);
1073 value
->type
= builtin_type_int
;
1078 gen_complement (struct agent_expr
*ax
, struct axs_value
*value
)
1080 if (TYPE_CODE (value
->type
) != TYPE_CODE_INT
)
1081 error ("Illegal type of operand to `~'.");
1083 gen_usual_unary (ax
, value
);
1084 gen_integral_promotions (ax
, value
);
1085 ax_simple (ax
, aop_bit_not
);
1086 gen_extend (ax
, value
->type
);
1091 /* Generating bytecode from GDB expressions: * & . -> @ sizeof */
1093 /* Dereference the value on the top of the stack. */
1095 gen_deref (struct agent_expr
*ax
, struct axs_value
*value
)
1097 /* The caller should check the type, because several operators use
1098 this, and we don't know what error message to generate. */
1099 if (TYPE_CODE (value
->type
) != TYPE_CODE_PTR
)
1100 internal_error (__FILE__
, __LINE__
,
1101 "gen_deref: expected a pointer");
1103 /* We've got an rvalue now, which is a pointer. We want to yield an
1104 lvalue, whose address is exactly that pointer. So we don't
1105 actually emit any code; we just change the type from "Pointer to
1106 T" to "T", and mark the value as an lvalue in memory. Leave it
1107 to the consumer to actually dereference it. */
1108 value
->type
= check_typedef (TYPE_TARGET_TYPE (value
->type
));
1109 value
->kind
= ((TYPE_CODE (value
->type
) == TYPE_CODE_FUNC
)
1110 ? axs_rvalue
: axs_lvalue_memory
);
1114 /* Produce the address of the lvalue on the top of the stack. */
1116 gen_address_of (struct agent_expr
*ax
, struct axs_value
*value
)
1118 /* Special case for taking the address of a function. The ANSI
1119 standard describes this as a special case, too, so this
1120 arrangement is not without motivation. */
1121 if (TYPE_CODE (value
->type
) == TYPE_CODE_FUNC
)
1122 /* The value's already an rvalue on the stack, so we just need to
1124 value
->type
= lookup_pointer_type (value
->type
);
1126 switch (value
->kind
)
1129 error ("Operand of `&' is an rvalue, which has no address.");
1131 case axs_lvalue_register
:
1132 error ("Operand of `&' is in a register, and has no address.");
1134 case axs_lvalue_memory
:
1135 value
->kind
= axs_rvalue
;
1136 value
->type
= lookup_pointer_type (value
->type
);
1142 /* A lot of this stuff will have to change to support C++. But we're
1143 not going to deal with that at the moment. */
1145 /* Find the field in the structure type TYPE named NAME, and return
1146 its index in TYPE's field array. */
1148 find_field (struct type
*type
, char *name
)
1152 CHECK_TYPEDEF (type
);
1154 /* Make sure this isn't C++. */
1155 if (TYPE_N_BASECLASSES (type
) != 0)
1156 internal_error (__FILE__
, __LINE__
,
1157 "find_field: derived classes supported");
1159 for (i
= 0; i
< TYPE_NFIELDS (type
); i
++)
1161 char *this_name
= TYPE_FIELD_NAME (type
, i
);
1163 if (this_name
&& strcmp (name
, this_name
) == 0)
1166 if (this_name
[0] == '\0')
1167 internal_error (__FILE__
, __LINE__
,
1168 "find_field: anonymous unions not supported");
1171 error ("Couldn't find member named `%s' in struct/union `%s'",
1172 name
, TYPE_TAG_NAME (type
));
1178 /* Generate code to push the value of a bitfield of a structure whose
1179 address is on the top of the stack. START and END give the
1180 starting and one-past-ending *bit* numbers of the field within the
1183 gen_bitfield_ref (struct agent_expr
*ax
, struct axs_value
*value
,
1184 struct type
*type
, int start
, int end
)
1186 /* Note that ops[i] fetches 8 << i bits. */
1187 static enum agent_op ops
[]
1189 {aop_ref8
, aop_ref16
, aop_ref32
, aop_ref64
};
1190 static int num_ops
= (sizeof (ops
) / sizeof (ops
[0]));
1192 /* We don't want to touch any byte that the bitfield doesn't
1193 actually occupy; we shouldn't make any accesses we're not
1194 explicitly permitted to. We rely here on the fact that the
1195 bytecode `ref' operators work on unaligned addresses.
1197 It takes some fancy footwork to get the stack to work the way
1198 we'd like. Say we're retrieving a bitfield that requires three
1199 fetches. Initially, the stack just contains the address:
1201 For the first fetch, we duplicate the address
1203 then add the byte offset, do the fetch, and shift and mask as
1204 needed, yielding a fragment of the value, properly aligned for
1205 the final bitwise or:
1207 then we swap, and repeat the process:
1208 frag1 addr --- address on top
1209 frag1 addr addr --- duplicate it
1210 frag1 addr frag2 --- get second fragment
1211 frag1 frag2 addr --- swap again
1212 frag1 frag2 frag3 --- get third fragment
1213 Notice that, since the third fragment is the last one, we don't
1214 bother duplicating the address this time. Now we have all the
1215 fragments on the stack, and we can simply `or' them together,
1216 yielding the final value of the bitfield. */
1218 /* The first and one-after-last bits in the field, but rounded down
1219 and up to byte boundaries. */
1220 int bound_start
= (start
/ TARGET_CHAR_BIT
) * TARGET_CHAR_BIT
;
1221 int bound_end
= (((end
+ TARGET_CHAR_BIT
- 1)
1225 /* current bit offset within the structure */
1228 /* The index in ops of the opcode we're considering. */
1231 /* The number of fragments we generated in the process. Probably
1232 equal to the number of `one' bits in bytesize, but who cares? */
1235 /* Dereference any typedefs. */
1236 type
= check_typedef (type
);
1238 /* Can we fetch the number of bits requested at all? */
1239 if ((end
- start
) > ((1 << num_ops
) * 8))
1240 internal_error (__FILE__
, __LINE__
,
1241 "gen_bitfield_ref: bitfield too wide");
1243 /* Note that we know here that we only need to try each opcode once.
1244 That may not be true on machines with weird byte sizes. */
1245 offset
= bound_start
;
1247 for (op
= num_ops
- 1; op
>= 0; op
--)
1249 /* number of bits that ops[op] would fetch */
1250 int op_size
= 8 << op
;
1252 /* The stack at this point, from bottom to top, contains zero or
1253 more fragments, then the address. */
1255 /* Does this fetch fit within the bitfield? */
1256 if (offset
+ op_size
<= bound_end
)
1258 /* Is this the last fragment? */
1259 int last_frag
= (offset
+ op_size
== bound_end
);
1262 ax_simple (ax
, aop_dup
); /* keep a copy of the address */
1264 /* Add the offset. */
1265 gen_offset (ax
, offset
/ TARGET_CHAR_BIT
);
1269 /* Record the area of memory we're about to fetch. */
1270 ax_trace_quick (ax
, op_size
/ TARGET_CHAR_BIT
);
1273 /* Perform the fetch. */
1274 ax_simple (ax
, ops
[op
]);
1276 /* Shift the bits we have to their proper position.
1277 gen_left_shift will generate right shifts when the operand
1280 A big-endian field diagram to ponder:
1281 byte 0 byte 1 byte 2 byte 3 byte 4 byte 5 byte 6 byte 7
1282 +------++------++------++------++------++------++------++------+
1283 xxxxAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBCCCCCxxxxxxxxxxx
1285 bit number 16 32 48 53
1286 These are bit numbers as supplied by GDB. Note that the
1287 bit numbers run from right to left once you've fetched the
1290 A little-endian field diagram to ponder:
1291 byte 7 byte 6 byte 5 byte 4 byte 3 byte 2 byte 1 byte 0
1292 +------++------++------++------++------++------++------++------+
1293 xxxxxxxxxxxAAAAABBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCCCCCCCCCCCCCxxxx
1295 bit number 48 32 16 4 0
1297 In both cases, the most significant end is on the left
1298 (i.e. normal numeric writing order), which means that you
1299 don't go crazy thinking about `left' and `right' shifts.
1301 We don't have to worry about masking yet:
1302 - If they contain garbage off the least significant end, then we
1303 must be looking at the low end of the field, and the right
1304 shift will wipe them out.
1305 - If they contain garbage off the most significant end, then we
1306 must be looking at the most significant end of the word, and
1307 the sign/zero extension will wipe them out.
1308 - If we're in the interior of the word, then there is no garbage
1309 on either end, because the ref operators zero-extend. */
1310 if (TARGET_BYTE_ORDER
== BFD_ENDIAN_BIG
)
1311 gen_left_shift (ax
, end
- (offset
+ op_size
));
1313 gen_left_shift (ax
, offset
- start
);
1316 /* Bring the copy of the address up to the top. */
1317 ax_simple (ax
, aop_swap
);
1324 /* Generate enough bitwise `or' operations to combine all the
1325 fragments we left on the stack. */
1326 while (fragment_count
-- > 1)
1327 ax_simple (ax
, aop_bit_or
);
1329 /* Sign- or zero-extend the value as appropriate. */
1330 ((TYPE_UNSIGNED (type
) ? ax_zero_ext
: ax_ext
) (ax
, end
- start
));
1332 /* This is *not* an lvalue. Ugh. */
1333 value
->kind
= axs_rvalue
;
1338 /* Generate code to reference the member named FIELD of a structure or
1339 union. The top of the stack, as described by VALUE, should have
1340 type (pointer to a)* struct/union. OPERATOR_NAME is the name of
1341 the operator being compiled, and OPERAND_NAME is the kind of thing
1342 it operates on; we use them in error messages. */
1344 gen_struct_ref (struct agent_expr
*ax
, struct axs_value
*value
, char *field
,
1345 char *operator_name
, char *operand_name
)
1350 /* Follow pointers until we reach a non-pointer. These aren't the C
1351 semantics, but they're what the normal GDB evaluator does, so we
1352 should at least be consistent. */
1353 while (TYPE_CODE (value
->type
) == TYPE_CODE_PTR
)
1355 gen_usual_unary (ax
, value
);
1356 gen_deref (ax
, value
);
1358 type
= check_typedef (value
->type
);
1360 /* This must yield a structure or a union. */
1361 if (TYPE_CODE (type
) != TYPE_CODE_STRUCT
1362 && TYPE_CODE (type
) != TYPE_CODE_UNION
)
1363 error ("The left operand of `%s' is not a %s.",
1364 operator_name
, operand_name
);
1366 /* And it must be in memory; we don't deal with structure rvalues,
1367 or structures living in registers. */
1368 if (value
->kind
!= axs_lvalue_memory
)
1369 error ("Structure does not live in memory.");
1371 i
= find_field (type
, field
);
1373 /* Is this a bitfield? */
1374 if (TYPE_FIELD_PACKED (type
, i
))
1375 gen_bitfield_ref (ax
, value
, TYPE_FIELD_TYPE (type
, i
),
1376 TYPE_FIELD_BITPOS (type
, i
),
1377 (TYPE_FIELD_BITPOS (type
, i
)
1378 + TYPE_FIELD_BITSIZE (type
, i
)));
1381 gen_offset (ax
, TYPE_FIELD_BITPOS (type
, i
) / TARGET_CHAR_BIT
);
1382 value
->kind
= axs_lvalue_memory
;
1383 value
->type
= TYPE_FIELD_TYPE (type
, i
);
1388 /* Generate code for GDB's magical `repeat' operator.
1389 LVALUE @ INT creates an array INT elements long, and whose elements
1390 have the same type as LVALUE, located in memory so that LVALUE is
1391 its first element. For example, argv[0]@argc gives you the array
1392 of command-line arguments.
1394 Unfortunately, because we have to know the types before we actually
1395 have a value for the expression, we can't implement this perfectly
1396 without changing the type system, having values that occupy two
1397 stack slots, doing weird things with sizeof, etc. So we require
1398 the right operand to be a constant expression. */
1400 gen_repeat (union exp_element
**pc
, struct agent_expr
*ax
,
1401 struct axs_value
*value
)
1403 struct axs_value value1
;
1404 /* We don't want to turn this into an rvalue, so no conversions
1406 gen_expr (pc
, ax
, &value1
);
1407 if (value1
.kind
!= axs_lvalue_memory
)
1408 error ("Left operand of `@' must be an object in memory.");
1410 /* Evaluate the length; it had better be a constant. */
1412 struct value
*v
= const_expr (pc
);
1416 error ("Right operand of `@' must be a constant, in agent expressions.");
1417 if (TYPE_CODE (v
->type
) != TYPE_CODE_INT
)
1418 error ("Right operand of `@' must be an integer.");
1419 length
= value_as_long (v
);
1421 error ("Right operand of `@' must be positive.");
1423 /* The top of the stack is already the address of the object, so
1424 all we need to do is frob the type of the lvalue. */
1426 /* FIXME-type-allocation: need a way to free this type when we are
1429 = create_range_type (0, builtin_type_int
, 0, length
- 1);
1430 struct type
*array
= create_array_type (0, value1
.type
, range
);
1432 value
->kind
= axs_lvalue_memory
;
1433 value
->type
= array
;
1439 /* Emit code for the `sizeof' operator.
1440 *PC should point at the start of the operand expression; we advance it
1441 to the first instruction after the operand. */
1443 gen_sizeof (union exp_element
**pc
, struct agent_expr
*ax
,
1444 struct axs_value
*value
)
1446 /* We don't care about the value of the operand expression; we only
1447 care about its type. However, in the current arrangement, the
1448 only way to find an expression's type is to generate code for it.
1449 So we generate code for the operand, and then throw it away,
1450 replacing it with code that simply pushes its size. */
1451 int start
= ax
->len
;
1452 gen_expr (pc
, ax
, value
);
1454 /* Throw away the code we just generated. */
1457 ax_const_l (ax
, TYPE_LENGTH (value
->type
));
1458 value
->kind
= axs_rvalue
;
1459 value
->type
= builtin_type_int
;
1463 /* Generating bytecode from GDB expressions: general recursive thingy */
1465 /* A gen_expr function written by a Gen-X'er guy.
1466 Append code for the subexpression of EXPR starting at *POS_P to AX. */
1468 gen_expr (union exp_element
**pc
, struct agent_expr
*ax
,
1469 struct axs_value
*value
)
1471 /* Used to hold the descriptions of operand expressions. */
1472 struct axs_value value1
, value2
;
1473 enum exp_opcode op
= (*pc
)[0].opcode
;
1475 /* If we're looking at a constant expression, just push its value. */
1477 struct value
*v
= maybe_const_expr (pc
);
1481 ax_const_l (ax
, value_as_long (v
));
1482 value
->kind
= axs_rvalue
;
1483 value
->type
= check_typedef (VALUE_TYPE (v
));
1488 /* Otherwise, go ahead and generate code for it. */
1491 /* Binary arithmetic operators. */
1497 case BINOP_SUBSCRIPT
:
1498 case BINOP_BITWISE_AND
:
1499 case BINOP_BITWISE_IOR
:
1500 case BINOP_BITWISE_XOR
:
1502 gen_expr (pc
, ax
, &value1
);
1503 gen_usual_unary (ax
, &value1
);
1504 gen_expr (pc
, ax
, &value2
);
1505 gen_usual_unary (ax
, &value2
);
1506 gen_usual_arithmetic (ax
, &value1
, &value2
);
1510 gen_add (ax
, value
, &value1
, &value2
, "addition");
1513 gen_sub (ax
, value
, &value1
, &value2
);
1516 gen_binop (ax
, value
, &value1
, &value2
,
1517 aop_mul
, aop_mul
, 1, "multiplication");
1520 gen_binop (ax
, value
, &value1
, &value2
,
1521 aop_div_signed
, aop_div_unsigned
, 1, "division");
1524 gen_binop (ax
, value
, &value1
, &value2
,
1525 aop_rem_signed
, aop_rem_unsigned
, 1, "remainder");
1527 case BINOP_SUBSCRIPT
:
1528 gen_add (ax
, value
, &value1
, &value2
, "array subscripting");
1529 if (TYPE_CODE (value
->type
) != TYPE_CODE_PTR
)
1530 error ("Illegal combination of types in array subscripting.");
1531 gen_deref (ax
, value
);
1533 case BINOP_BITWISE_AND
:
1534 gen_binop (ax
, value
, &value1
, &value2
,
1535 aop_bit_and
, aop_bit_and
, 0, "bitwise and");
1538 case BINOP_BITWISE_IOR
:
1539 gen_binop (ax
, value
, &value1
, &value2
,
1540 aop_bit_or
, aop_bit_or
, 0, "bitwise or");
1543 case BINOP_BITWISE_XOR
:
1544 gen_binop (ax
, value
, &value1
, &value2
,
1545 aop_bit_xor
, aop_bit_xor
, 0, "bitwise exclusive-or");
1549 /* We should only list operators in the outer case statement
1550 that we actually handle in the inner case statement. */
1551 internal_error (__FILE__
, __LINE__
,
1552 "gen_expr: op case sets don't match");
1556 /* Note that we need to be a little subtle about generating code
1557 for comma. In C, we can do some optimizations here because
1558 we know the left operand is only being evaluated for effect.
1559 However, if the tracing kludge is in effect, then we always
1560 need to evaluate the left hand side fully, so that all the
1561 variables it mentions get traced. */
1564 gen_expr (pc
, ax
, &value1
);
1565 /* Don't just dispose of the left operand. We might be tracing,
1566 in which case we want to emit code to trace it if it's an
1568 gen_traced_pop (ax
, &value1
);
1569 gen_expr (pc
, ax
, value
);
1570 /* It's the consumer's responsibility to trace the right operand. */
1573 case OP_LONG
: /* some integer constant */
1575 struct type
*type
= (*pc
)[1].type
;
1576 LONGEST k
= (*pc
)[2].longconst
;
1578 gen_int_literal (ax
, value
, k
, type
);
1583 gen_var_ref (ax
, value
, (*pc
)[2].symbol
);
1589 int reg
= (int) (*pc
)[1].longconst
;
1591 value
->kind
= axs_lvalue_register
;
1593 value
->type
= REGISTER_VIRTUAL_TYPE (reg
);
1597 case OP_INTERNALVAR
:
1598 error ("GDB agent expressions cannot use convenience variables.");
1600 /* Weirdo operator: see comments for gen_repeat for details. */
1602 /* Note that gen_repeat handles its own argument evaluation. */
1604 gen_repeat (pc
, ax
, value
);
1609 struct type
*type
= (*pc
)[1].type
;
1611 gen_expr (pc
, ax
, value
);
1612 gen_cast (ax
, value
, type
);
1618 struct type
*type
= check_typedef ((*pc
)[1].type
);
1620 gen_expr (pc
, ax
, value
);
1621 /* I'm not sure I understand UNOP_MEMVAL entirely. I think
1622 it's just a hack for dealing with minsyms; you take some
1623 integer constant, pretend it's the address of an lvalue of
1624 the given type, and dereference it. */
1625 if (value
->kind
!= axs_rvalue
)
1626 /* This would be weird. */
1627 internal_error (__FILE__
, __LINE__
,
1628 "gen_expr: OP_MEMVAL operand isn't an rvalue???");
1630 value
->kind
= axs_lvalue_memory
;
1636 /* -FOO is equivalent to 0 - FOO. */
1637 gen_int_literal (ax
, &value1
, (LONGEST
) 0, builtin_type_int
);
1638 gen_usual_unary (ax
, &value1
); /* shouldn't do much */
1639 gen_expr (pc
, ax
, &value2
);
1640 gen_usual_unary (ax
, &value2
);
1641 gen_usual_arithmetic (ax
, &value1
, &value2
);
1642 gen_sub (ax
, value
, &value1
, &value2
);
1645 case UNOP_LOGICAL_NOT
:
1647 gen_expr (pc
, ax
, value
);
1648 gen_logical_not (ax
, value
);
1651 case UNOP_COMPLEMENT
:
1653 gen_expr (pc
, ax
, value
);
1654 gen_complement (ax
, value
);
1659 gen_expr (pc
, ax
, value
);
1660 gen_usual_unary (ax
, value
);
1661 if (TYPE_CODE (value
->type
) != TYPE_CODE_PTR
)
1662 error ("Argument of unary `*' is not a pointer.");
1663 gen_deref (ax
, value
);
1668 gen_expr (pc
, ax
, value
);
1669 gen_address_of (ax
, value
);
1674 /* Notice that gen_sizeof handles its own operand, unlike most
1675 of the other unary operator functions. This is because we
1676 have to throw away the code we generate. */
1677 gen_sizeof (pc
, ax
, value
);
1680 case STRUCTOP_STRUCT
:
1683 int length
= (*pc
)[1].longconst
;
1684 char *name
= &(*pc
)[2].string
;
1686 (*pc
) += 4 + BYTES_TO_EXP_ELEM (length
+ 1);
1687 gen_expr (pc
, ax
, value
);
1688 if (op
== STRUCTOP_STRUCT
)
1689 gen_struct_ref (ax
, value
, name
, ".", "structure or union");
1690 else if (op
== STRUCTOP_PTR
)
1691 gen_struct_ref (ax
, value
, name
, "->",
1692 "pointer to a structure or union");
1694 /* If this `if' chain doesn't handle it, then the case list
1695 shouldn't mention it, and we shouldn't be here. */
1696 internal_error (__FILE__
, __LINE__
,
1697 "gen_expr: unhandled struct case");
1702 error ("Attempt to use a type name as an expression.");
1705 error ("Unsupported operator in expression.");
1711 /* Generating bytecode from GDB expressions: driver */
1713 /* Given a GDB expression EXPR, produce a string of agent bytecode
1714 which computes its value. Return the agent expression, and set
1715 *VALUE to describe its type, and whether it's an lvalue or rvalue. */
1717 expr_to_agent (struct expression
*expr
, struct axs_value
*value
)
1719 struct cleanup
*old_chain
= 0;
1720 struct agent_expr
*ax
= new_agent_expr (0);
1721 union exp_element
*pc
;
1723 old_chain
= make_cleanup_free_agent_expr (ax
);
1727 gen_expr (&pc
, ax
, value
);
1729 /* We have successfully built the agent expr, so cancel the cleanup
1730 request. If we add more cleanups that we always want done, this
1731 will have to get more complicated. */
1732 discard_cleanups (old_chain
);
1737 #if 0 /* not used */
1738 /* Given a GDB expression EXPR denoting an lvalue in memory, produce a
1739 string of agent bytecode which will leave its address and size on
1740 the top of stack. Return the agent expression.
1742 Not sure this function is useful at all. */
1744 expr_to_address_and_size (struct expression
*expr
)
1746 struct axs_value value
;
1747 struct agent_expr
*ax
= expr_to_agent (expr
, &value
);
1749 /* Complain if the result is not a memory lvalue. */
1750 if (value
.kind
!= axs_lvalue_memory
)
1752 free_agent_expr (ax
);
1753 error ("Expression does not denote an object in memory.");
1756 /* Push the object's size on the stack. */
1757 ax_const_l (ax
, TYPE_LENGTH (value
.type
));
1763 /* Given a GDB expression EXPR, return bytecode to trace its value.
1764 The result will use the `trace' and `trace_quick' bytecodes to
1765 record the value of all memory touched by the expression. The
1766 caller can then use the ax_reqs function to discover which
1767 registers it relies upon. */
1769 gen_trace_for_expr (CORE_ADDR scope
, struct expression
*expr
)
1771 struct cleanup
*old_chain
= 0;
1772 struct agent_expr
*ax
= new_agent_expr (scope
);
1773 union exp_element
*pc
;
1774 struct axs_value value
;
1776 old_chain
= make_cleanup_free_agent_expr (ax
);
1780 gen_expr (&pc
, ax
, &value
);
1782 /* Make sure we record the final object, and get rid of it. */
1783 gen_traced_pop (ax
, &value
);
1785 /* Oh, and terminate. */
1786 ax_simple (ax
, aop_end
);
1788 /* We have successfully built the agent expr, so cancel the cleanup
1789 request. If we add more cleanups that we always want done, this
1790 will have to get more complicated. */
1791 discard_cleanups (old_chain
);
1797 /* The "agent" command, for testing: compile and disassemble an expression. */
1800 print_axs_value (struct ui_file
*f
, struct axs_value
*value
)
1802 switch (value
->kind
)
1805 fputs_filtered ("rvalue", f
);
1808 case axs_lvalue_memory
:
1809 fputs_filtered ("memory lvalue", f
);
1812 case axs_lvalue_register
:
1813 fprintf_filtered (f
, "register %d lvalue", value
->u
.reg
);
1817 fputs_filtered (" : ", f
);
1818 type_print (value
->type
, "", f
, -1);
1823 agent_command (char *exp
, int from_tty
)
1825 struct cleanup
*old_chain
= 0;
1826 struct expression
*expr
;
1827 struct agent_expr
*agent
;
1828 struct frame_info
*fi
= get_current_frame (); /* need current scope */
1830 /* We don't deal with overlay debugging at the moment. We need to
1831 think more carefully about this. If you copy this code into
1832 another command, change the error message; the user shouldn't
1833 have to know anything about agent expressions. */
1834 if (overlay_debugging
)
1835 error ("GDB can't do agent expression translation with overlays.");
1838 error_no_arg ("expression to translate");
1840 expr
= parse_expression (exp
);
1841 old_chain
= make_cleanup (free_current_contents
, &expr
);
1842 agent
= gen_trace_for_expr (get_frame_pc (fi
), expr
);
1843 make_cleanup_free_agent_expr (agent
);
1844 ax_print (gdb_stdout
, agent
);
1846 /* It would be nice to call ax_reqs here to gather some general info
1847 about the expression, and then print out the result. */
1849 do_cleanups (old_chain
);
1854 /* Initialization code. */
1856 void _initialize_ax_gdb (void);
1858 _initialize_ax_gdb (void)
1860 add_cmd ("agent", class_maintenance
, agent_command
,
1861 "Translate an expression into remote agent bytecode.",