--- /dev/null
+/* GDB-specific functions for operating on agent expressions
+ Copyright 1998 Free Software Foundation, Inc.
+
+This file is part of GDB.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+/* $Id$ */
+
+#include "defs.h"
+#include "symtab.h"
+#include "symfile.h"
+#include "gdbtypes.h"
+#include "value.h"
+#include "expression.h"
+#include "command.h"
+#include "gdbcmd.h"
+#include "ax.h"
+#include "ax-gdb.h"
+
+/* Probably the best way to read this file is to start with the types
+ and enums in ax-gdb.h, and then look at gen_expr, towards the
+ bottom; that's the main function that looks at the GDB expressions
+ and calls everything else to generate code.
+
+ I'm beginning to wonder whether it wouldn't be nicer to internally
+ generate trees, with types, and then spit out the bytecode in
+ linear form afterwards; we could generate fewer `swap', `ext', and
+ `zero_ext' bytecodes that way; it would make good constant folding
+ easier, too. But at the moment, I think we should be willing to
+ pay for the simplicity of this code with less-than-optimal bytecode
+ strings.
+
+ Remember, "GBD" stands for "Great Britain, Dammit!" So be careful. */
+
+
+\f
+/* Static forward declarations */
+
+/* There's a standard order to the arguments of these functions:
+ union exp_element ** --- pointer into expression
+ struct agent_expr * --- agent expression buffer to generate code into
+ struct axs_value * --- describes value left on top of stack */
+
+static struct value *const_var_ref PARAMS ((struct symbol *var));
+static struct value *const_expr PARAMS ((union exp_element **pc));
+static struct value *maybe_const_expr PARAMS ((union exp_element **pc));
+
+static void gen_traced_pop PARAMS ((struct agent_expr *, struct axs_value *));
+
+static void gen_sign_extend PARAMS ((struct agent_expr *, struct type *));
+static void gen_extend PARAMS ((struct agent_expr *, struct type *));
+static void gen_fetch PARAMS ((struct agent_expr *, struct type *));
+static void gen_left_shift PARAMS ((struct agent_expr *, int));
+
+
+static void gen_frame_args_address PARAMS ((struct agent_expr *));
+static void gen_frame_locals_address PARAMS ((struct agent_expr *));
+static void gen_offset PARAMS ((struct agent_expr *ax, int offset));
+static void gen_sym_offset PARAMS ((struct agent_expr *, struct symbol *));
+static void gen_var_ref PARAMS ((struct agent_expr *ax,
+ struct axs_value *value,
+ struct symbol *var));
+
+
+static void gen_int_literal PARAMS ((struct agent_expr *ax,
+ struct axs_value *value,
+ LONGEST k, struct type *type));
+
+
+static void require_rvalue PARAMS ((struct agent_expr *ax,
+ struct axs_value *value));
+static void gen_usual_unary PARAMS ((struct agent_expr *ax,
+ struct axs_value *value));
+static int type_wider_than PARAMS ((struct type *type1,
+ struct type *type2));
+static struct type *max_type PARAMS ((struct type *type1,
+ struct type *type2));
+static void gen_conversion PARAMS ((struct agent_expr *ax,
+ struct type *from,
+ struct type *to));
+static int is_nontrivial_conversion PARAMS ((struct type *from,
+ struct type *to));
+static void gen_usual_arithmetic PARAMS ((struct agent_expr *ax,
+ struct axs_value *value1,
+ struct axs_value *value2));
+static void gen_integral_promotions PARAMS ((struct agent_expr *ax,
+ struct axs_value *value));
+static void gen_cast PARAMS ((struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *type));
+static void gen_scale PARAMS ((struct agent_expr *ax,
+ enum agent_op op,
+ struct type *type));
+static void gen_add PARAMS ((struct agent_expr *ax,
+ struct axs_value *value,
+ struct axs_value *value1,
+ struct axs_value *value2,
+ char *name));
+static void gen_sub PARAMS ((struct agent_expr *ax,
+ struct axs_value *value,
+ struct axs_value *value1,
+ struct axs_value *value2));
+static void gen_binop PARAMS ((struct agent_expr *ax,
+ struct axs_value *value,
+ struct axs_value *value1,
+ struct axs_value *value2,
+ enum agent_op op,
+ enum agent_op op_unsigned,
+ int may_carry,
+ char *name));
+static void gen_logical_not PARAMS ((struct agent_expr *ax,
+ struct axs_value *value));
+static void gen_complement PARAMS ((struct agent_expr *ax,
+ struct axs_value *value));
+static void gen_deref PARAMS ((struct agent_expr *, struct axs_value *));
+static void gen_address_of PARAMS ((struct agent_expr *, struct axs_value *));
+static int find_field PARAMS ((struct type *type, char *name));
+static void gen_bitfield_ref PARAMS ((struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *type,
+ int start, int end));
+static void gen_struct_ref PARAMS ((struct agent_expr *ax,
+ struct axs_value *value,
+ char *field,
+ char *operator_name,
+ char *operand_name));
+static void gen_repeat PARAMS ((union exp_element **pc,
+ struct agent_expr *ax,
+ struct axs_value *value));
+static void gen_sizeof PARAMS ((union exp_element **pc,
+ struct agent_expr *ax,
+ struct axs_value *value));
+static void gen_expr PARAMS ((union exp_element **pc,
+ struct agent_expr *ax,
+ struct axs_value *value));
+static void print_axs_value PARAMS ((GDB_FILE *f, struct axs_value *value));
+static void agent_command PARAMS ((char *exp, int from_tty));
+
+\f
+/* Detecting constant expressions. */
+
+/* If the variable reference at *PC is a constant, return its value.
+ Otherwise, return zero.
+
+ Hey, Wally! How can a variable reference be a constant?
+
+ Well, Beav, this function really handles the OP_VAR_VALUE operator,
+ not specifically variable references. GDB uses OP_VAR_VALUE to
+ refer to any kind of symbolic reference: function names, enum
+ elements, and goto labels are all handled through the OP_VAR_VALUE
+ operator, even though they're constants. It makes sense given the
+ situation.
+
+ Gee, Wally, don'cha wonder sometimes if data representations that
+ subvert commonly accepted definitions of terms in favor of heavily
+ context-specific interpretations are really just a tool of the
+ programming hegemony to preserve their power and exclude the
+ proletariat? */
+
+static struct value *
+const_var_ref (var)
+ struct symbol *var;
+{
+ struct type *type = SYMBOL_TYPE (var);
+
+ switch (SYMBOL_CLASS (var))
+ {
+ case LOC_CONST:
+ return value_from_longest (type, (LONGEST) SYMBOL_VALUE (var));
+
+ case LOC_LABEL:
+ return value_from_longest (type, (LONGEST) SYMBOL_VALUE_ADDRESS (var));
+
+ default:
+ return 0;
+ }
+}
+
+
+/* If the expression starting at *PC has a constant value, return it.
+ Otherwise, return zero. If we return a value, then *PC will be
+ advanced to the end of it. If we return zero, *PC could be
+ anywhere. */
+static struct value *
+const_expr (pc)
+ union exp_element **pc;
+{
+ enum exp_opcode op = (*pc)->opcode;
+ struct value *v1;
+
+ switch (op)
+ {
+ case OP_LONG:
+ {
+ struct type *type = (*pc)[1].type;
+ LONGEST k = (*pc)[2].longconst;
+ (*pc) += 4;
+ return value_from_longest (type, k);
+ }
+
+ case OP_VAR_VALUE:
+ {
+ struct value *v = const_var_ref ((*pc)[2].symbol);
+ (*pc) += 4;
+ return v;
+ }
+
+ /* We could add more operators in here. */
+
+ case UNOP_NEG:
+ (*pc)++;
+ v1 = const_expr (pc);
+ if (v1)
+ return value_neg (v1);
+ else
+ return 0;
+
+ default:
+ return 0;
+ }
+}
+
+
+/* Like const_expr, but guarantee also that *PC is undisturbed if the
+ expression is not constant. */
+static struct value *
+maybe_const_expr (pc)
+ union exp_element **pc;
+{
+ union exp_element *tentative_pc = *pc;
+ struct value *v = const_expr (&tentative_pc);
+
+ /* If we got a value, then update the real PC. */
+ if (v)
+ *pc = tentative_pc;
+
+ return v;
+}
+
+\f
+/* Generating bytecode from GDB expressions: general assumptions */
+
+/* Here are a few general assumptions made throughout the code; if you
+ want to make a change that contradicts one of these, then you'd
+ better scan things pretty thoroughly.
+
+ - We assume that all values occupy one stack element. For example,
+ sometimes we'll swap to get at the left argument to a binary
+ operator. If we decide that void values should occupy no stack
+ elements, or that synthetic arrays (whose size is determined at
+ run time, created by the `@' operator) should occupy two stack
+ elements (address and length), then this will cause trouble.
+
+ - We assume the stack elements are infinitely wide, and that we
+ don't have to worry what happens if the user requests an
+ operation that is wider than the actual interpreter's stack.
+ That is, it's up to the interpreter to handle directly all the
+ integer widths the user has access to. (Woe betide the language
+ with bignums!)
+
+ - We don't support side effects. Thus, we don't have to worry about
+ GCC's generalized lvalues, function calls, etc.
+
+ - We don't support floating point. Many places where we switch on
+ some type don't bother to include cases for floating point; there
+ may be even more subtle ways this assumption exists. For
+ example, the arguments to % must be integers.
+
+ - We assume all subexpressions have a static, unchanging type. If
+ we tried to support convenience variables, this would be a
+ problem.
+
+ - All values on the stack should always be fully zero- or
+ sign-extended.
+
+ (I wasn't sure whether to choose this or its opposite --- that
+ only addresses are assumed extended --- but it turns out that
+ neither convention completely eliminates spurious extend
+ operations (if everything is always extended, then you have to
+ extend after add, because it could overflow; if nothing is
+ extended, then you end up producing extends whenever you change
+ sizes), and this is simpler.) */
+
+\f
+/* Generating bytecode from GDB expressions: the `trace' kludge */
+
+/* The compiler in this file is a general-purpose mechanism for
+ translating GDB expressions into bytecode. One ought to be able to
+ find a million and one uses for it.
+
+ However, at the moment it is HOPELESSLY BRAIN-DAMAGED for the sake
+ of expediency. Let he who is without sin cast the first stone.
+
+ For the data tracing facility, we need to insert `trace' bytecodes
+ before each data fetch; this records all the memory that the
+ expression touches in the course of evaluation, so that memory will
+ be available when the user later tries to evaluate the expression
+ in GDB.
+
+ This should be done (I think) in a post-processing pass, that walks
+ an arbitrary agent expression and inserts `trace' operations at the
+ appropriate points. But it's much faster to just hack them
+ directly into the code. And since we're in a crunch, that's what
+ I've done.
+
+ Setting the flag trace_kludge to non-zero enables the code that
+ emits the trace bytecodes at the appropriate points. */
+static int trace_kludge;
+
+/* Trace the lvalue on the stack, if it needs it. In either case, pop
+ the value. Useful on the left side of a comma, and at the end of
+ an expression being used for tracing. */
+static void
+gen_traced_pop (ax, value)
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ if (trace_kludge)
+ switch (value->kind)
+ {
+ case axs_rvalue:
+ /* We don't trace rvalues, just the lvalues necessary to
+ produce them. So just dispose of this value. */
+ ax_simple (ax, aop_pop);
+ break;
+
+ case axs_lvalue_memory:
+ {
+ int length = TYPE_LENGTH (value->type);
+
+ /* There's no point in trying to use a trace_quick bytecode
+ here, since "trace_quick SIZE pop" is three bytes, whereas
+ "const8 SIZE trace" is also three bytes, does the same
+ thing, and the simplest code which generates that will also
+ work correctly for objects with large sizes. */
+ ax_const_l (ax, length);
+ ax_simple (ax, aop_trace);
+ }
+ break;
+
+ case axs_lvalue_register:
+ /* We need to mention the register somewhere in the bytecode,
+ so ax_reqs will pick it up and add it to the mask of
+ registers used. */
+ ax_reg (ax, value->u.reg);
+ ax_simple (ax, aop_pop);
+ break;
+ }
+ else
+ /* If we're not tracing, just pop the value. */
+ ax_simple (ax, aop_pop);
+}
+
+
+\f
+/* Generating bytecode from GDB expressions: helper functions */
+
+/* Assume that the lower bits of the top of the stack is a value of
+ type TYPE, and the upper bits are zero. Sign-extend if necessary. */
+static void
+gen_sign_extend (ax, type)
+ struct agent_expr *ax;
+ struct type *type;
+{
+ /* Do we need to sign-extend this? */
+ if (! TYPE_UNSIGNED (type))
+ ax_ext (ax, type->length * TARGET_CHAR_BIT);
+}
+
+
+/* Assume the lower bits of the top of the stack hold a value of type
+ TYPE, and the upper bits are garbage. Sign-extend or truncate as
+ needed. */
+static void
+gen_extend (ax, type)
+ struct agent_expr *ax;
+ struct type *type;
+{
+ int bits = type->length * TARGET_CHAR_BIT;
+ /* I just had to. */
+ ((TYPE_UNSIGNED (type) ? ax_zero_ext : ax_ext) (ax, bits));
+}
+
+
+/* Assume that the top of the stack contains a value of type "pointer
+ to TYPE"; generate code to fetch its value. Note that TYPE is the
+ target type, not the pointer type. */
+static void
+gen_fetch (ax, type)
+ struct agent_expr *ax;
+ struct type *type;
+{
+ if (trace_kludge)
+ {
+ /* Record the area of memory we're about to fetch. */
+ ax_trace_quick (ax, TYPE_LENGTH (type));
+ }
+
+ switch (type->code)
+ {
+ case TYPE_CODE_PTR:
+ case TYPE_CODE_ENUM:
+ case TYPE_CODE_INT:
+ case TYPE_CODE_CHAR:
+ /* It's a scalar value, so we know how to dereference it. How
+ many bytes long is it? */
+ switch (type->length)
+ {
+ case 8 / TARGET_CHAR_BIT: ax_simple (ax, aop_ref8 ); break;
+ case 16 / TARGET_CHAR_BIT: ax_simple (ax, aop_ref16); break;
+ case 32 / TARGET_CHAR_BIT: ax_simple (ax, aop_ref32); break;
+ case 64 / TARGET_CHAR_BIT: ax_simple (ax, aop_ref64); break;
+
+ /* Either our caller shouldn't have asked us to dereference
+ that pointer (other code's fault), or we're not
+ implementing something we should be (this code's fault).
+ In any case, it's a bug the user shouldn't see. */
+ default:
+ error ("GDB bug: ax-gdb.c (gen_fetch): strange size");
+ }
+
+ gen_sign_extend (ax, type);
+ break;
+
+ default:
+ /* Either our caller shouldn't have asked us to dereference that
+ pointer (other code's fault), or we're not implementing
+ something we should be (this code's fault). In any case,
+ it's a bug the user shouldn't see. */
+ error ("GDB bug: ax-gdb.c (gen_fetch): bad type code");
+ }
+}
+
+
+/* Generate code to left shift the top of the stack by DISTANCE bits, or
+ right shift it by -DISTANCE bits if DISTANCE < 0. This generates
+ unsigned (logical) right shifts. */
+static void
+gen_left_shift (ax, distance)
+ struct agent_expr *ax;
+ int distance;
+{
+ if (distance > 0)
+ {
+ ax_const_l (ax, distance);
+ ax_simple (ax, aop_lsh);
+ }
+ else if (distance < 0)
+ {
+ ax_const_l (ax, -distance);
+ ax_simple (ax, aop_rsh_unsigned);
+ }
+}
+
+
+\f
+/* Generating bytecode from GDB expressions: symbol references */
+
+/* Generate code to push the base address of the argument portion of
+ the top stack frame. */
+static void
+gen_frame_args_address (ax)
+ struct agent_expr *ax;
+{
+ /* FIXME: I'm sure this is wrong for processors other than the 68k. */
+ ax_reg (ax, FP_REGNUM);
+}
+
+
+/* Generate code to push the base address of the locals portion of the
+ top stack frame. */
+static void
+gen_frame_locals_address (ax)
+ struct agent_expr *ax;
+{
+ /* FIXME: I'm sure this is wrong for processors other than the 68k. */
+ ax_reg (ax, FP_REGNUM);
+}
+
+
+/* Generate code to add OFFSET to the top of the stack. Try to
+ generate short and readable code. We use this for getting to
+ variables on the stack, and structure members. If we were
+ programming in ML, it would be clearer why these are the same
+ thing. */
+static void
+gen_offset (ax, offset)
+ struct agent_expr *ax;
+ int offset;
+{
+ /* It would suffice to simply push the offset and add it, but this
+ makes it easier to read positive and negative offsets in the
+ bytecode. */
+ if (offset > 0)
+ {
+ ax_const_l (ax, offset);
+ ax_simple (ax, aop_add);
+ }
+ else if (offset < 0)
+ {
+ ax_const_l (ax, -offset);
+ ax_simple (ax, aop_sub);
+ }
+}
+
+
+/* In many cases, a symbol's value is the offset from some other
+ address (stack frame, base register, etc.) Generate code to add
+ VAR's value to the top of the stack. */
+static void
+gen_sym_offset (ax, var)
+ struct agent_expr *ax;
+ struct symbol *var;
+{
+ gen_offset (ax, SYMBOL_VALUE (var));
+}
+
+
+/* Generate code for a variable reference to AX. The variable is the
+ symbol VAR. Set VALUE to describe the result. */
+
+static void
+gen_var_ref (ax, value, var)
+ struct agent_expr *ax;
+ struct axs_value *value;
+ struct symbol *var;
+{
+ /* Dereference any typedefs. */
+ value->type = check_typedef (SYMBOL_TYPE (var));
+
+ /* I'm imitating the code in read_var_value. */
+ switch (SYMBOL_CLASS (var))
+ {
+ case LOC_CONST: /* A constant, like an enum value. */
+ ax_const_l (ax, (LONGEST) SYMBOL_VALUE (var));
+ value->kind = axs_rvalue;
+ break;
+
+ case LOC_LABEL: /* A goto label, being used as a value. */
+ ax_const_l (ax, (LONGEST) SYMBOL_VALUE_ADDRESS (var));
+ value->kind = axs_rvalue;
+ break;
+
+ case LOC_CONST_BYTES:
+ error ("GDB bug: ax-gdb.c (gen_var_ref): LOC_CONST_BYTES symbols are not supported");
+
+ /* Variable at a fixed location in memory. Easy. */
+ case LOC_STATIC:
+ /* Push the address of the variable. */
+ ax_const_l (ax, SYMBOL_VALUE_ADDRESS (var));
+ value->kind = axs_lvalue_memory;
+ break;
+
+ case LOC_ARG: /* var lives in argument area of frame */
+ gen_frame_args_address (ax);
+ gen_sym_offset (ax, var);
+ value->kind = axs_lvalue_memory;
+ break;
+
+ case LOC_REF_ARG: /* As above, but the frame slot really
+ holds the address of the variable. */
+ gen_frame_args_address (ax);
+ gen_sym_offset (ax, var);
+ /* Don't assume any particular pointer size. */
+ gen_fetch (ax, lookup_pointer_type (builtin_type_void));
+ value->kind = axs_lvalue_memory;
+ break;
+
+ case LOC_LOCAL: /* var lives in locals area of frame */
+ case LOC_LOCAL_ARG:
+ gen_frame_locals_address (ax);
+ gen_sym_offset (ax, var);
+ value->kind = axs_lvalue_memory;
+ break;
+
+ case LOC_BASEREG: /* relative to some base register */
+ case LOC_BASEREG_ARG:
+ ax_reg (ax, SYMBOL_BASEREG (var));
+ gen_sym_offset (ax, var);
+ value->kind = axs_lvalue_memory;
+ break;
+
+ case LOC_TYPEDEF:
+ error ("Cannot compute value of typedef `%s'.",
+ SYMBOL_SOURCE_NAME (var));
+ break;
+
+ case LOC_BLOCK:
+ ax_const_l (ax, BLOCK_START (SYMBOL_BLOCK_VALUE (var)));
+ value->kind = axs_rvalue;
+ break;
+
+ case LOC_REGISTER:
+ case LOC_REGPARM:
+ /* Don't generate any code at all; in the process of treating
+ this as an lvalue or rvalue, the caller will generate the
+ right code. */
+ value->kind = axs_lvalue_register;
+ value->u.reg = SYMBOL_VALUE (var);
+ break;
+
+ /* A lot like LOC_REF_ARG, but the pointer lives directly in a
+ register, not on the stack. Simpler than LOC_REGISTER and
+ LOC_REGPARM, because it's just like any other case where the
+ thing has a real address. */
+ case LOC_REGPARM_ADDR:
+ ax_reg (ax, SYMBOL_VALUE (var));
+ value->kind = axs_lvalue_memory;
+ break;
+
+ case LOC_UNRESOLVED:
+ {
+ struct minimal_symbol *msym
+ = lookup_minimal_symbol (SYMBOL_NAME (var), NULL, NULL);
+ if (! msym)
+ error ("Couldn't resolve symbol `%s'.", SYMBOL_SOURCE_NAME (var));
+
+ /* Push the address of the variable. */
+ ax_const_l (ax, SYMBOL_VALUE_ADDRESS (msym));
+ value->kind = axs_lvalue_memory;
+ }
+ break;
+
+ case LOC_OPTIMIZED_OUT:
+ error ("The variable `%s' has been optimized out.",
+ SYMBOL_SOURCE_NAME (var));
+ break;
+
+ default:
+ error ("Cannot find value of botched symbol `%s'.",
+ SYMBOL_SOURCE_NAME (var));
+ break;
+ }
+}
+
+
+\f
+/* Generating bytecode from GDB expressions: literals */
+
+static void
+gen_int_literal (ax, value, k, type)
+ struct agent_expr *ax;
+ struct axs_value *value;
+ LONGEST k;
+ struct type *type;
+{
+ ax_const_l (ax, k);
+ value->kind = axs_rvalue;
+ value->type = type;
+}
+
+
+\f
+/* Generating bytecode from GDB expressions: unary conversions, casts */
+
+/* Take what's on the top of the stack (as described by VALUE), and
+ try to make an rvalue out of it. Signal an error if we can't do
+ that. */
+static void
+require_rvalue (ax, value)
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ switch (value->kind)
+ {
+ case axs_rvalue:
+ /* It's already an rvalue. */
+ break;
+
+ case axs_lvalue_memory:
+ /* The top of stack is the address of the object. Dereference. */
+ gen_fetch (ax, value->type);
+ break;
+
+ case axs_lvalue_register:
+ /* There's nothing on the stack, but value->u.reg is the
+ register number containing the value.
+
+ When we add floating-point support, this is going to have to
+ change. What about SPARC register pairs, for example? */
+ ax_reg (ax, value->u.reg);
+ gen_extend (ax, value->type);
+ break;
+ }
+
+ value->kind = axs_rvalue;
+}
+
+
+/* Assume the top of the stack is described by VALUE, and perform the
+ usual unary conversions. This is motivated by ANSI 6.2.2, but of
+ course GDB expressions are not ANSI; they're the mishmash union of
+ a bunch of languages. Rah.
+
+ NOTE! This function promises to produce an rvalue only when the
+ incoming value is of an appropriate type. In other words, the
+ consumer of the value this function produces may assume the value
+ is an rvalue only after checking its type.
+
+ The immediate issue is that if the user tries to use a structure or
+ union as an operand of, say, the `+' operator, we don't want to try
+ to convert that structure to an rvalue; require_rvalue will bomb on
+ structs and unions. Rather, we want to simply pass the struct
+ lvalue through unchanged, and let `+' raise an error. */
+
+static void
+gen_usual_unary (ax, value)
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ /* We don't have to generate any code for the usual integral
+ conversions, since values are always represented as full-width on
+ the stack. Should we tweak the type? */
+
+ /* Some types require special handling. */
+ switch (value->type->code)
+ {
+ /* Functions get converted to a pointer to the function. */
+ case TYPE_CODE_FUNC:
+ value->type = lookup_pointer_type (value->type);
+ value->kind = axs_rvalue; /* Should always be true, but just in case. */
+ break;
+
+ /* Arrays get converted to a pointer to their first element, and
+ are no longer an lvalue. */
+ case TYPE_CODE_ARRAY:
+ {
+ struct type *elements = TYPE_TARGET_TYPE (value->type);
+ value->type = lookup_pointer_type (elements);
+ value->kind = axs_rvalue;
+ /* We don't need to generate any code; the address of the array
+ is also the address of its first element. */
+ }
+ break;
+
+ /* Don't try to convert structures and unions to rvalues. Let the
+ consumer signal an error. */
+ case TYPE_CODE_STRUCT:
+ case TYPE_CODE_UNION:
+ return;
+
+ /* If the value is an enum, call it an integer. */
+ case TYPE_CODE_ENUM:
+ value->type = builtin_type_int;
+ break;
+ }
+
+ /* If the value is an lvalue, dereference it. */
+ require_rvalue (ax, value);
+}
+
+
+/* Return non-zero iff the type TYPE1 is considered "wider" than the
+ type TYPE2, according to the rules described in gen_usual_arithmetic. */
+static int
+type_wider_than (type1, type2)
+ struct type *type1, *type2;
+{
+ return (TYPE_LENGTH (type1) > TYPE_LENGTH (type2)
+ || (TYPE_LENGTH (type1) == TYPE_LENGTH (type2)
+ && TYPE_UNSIGNED (type1)
+ && ! TYPE_UNSIGNED (type2)));
+}
+
+
+/* Return the "wider" of the two types TYPE1 and TYPE2. */
+static struct type *
+max_type (type1, type2)
+ struct type *type1, *type2;
+{
+ return type_wider_than (type1, type2) ? type1 : type2;
+}
+
+
+/* Generate code to convert a scalar value of type FROM to type TO. */
+static void
+gen_conversion (ax, from, to)
+ struct agent_expr *ax;
+ struct type *from, *to;
+{
+ /* Perhaps there is a more graceful way to state these rules. */
+
+ /* If we're converting to a narrower type, then we need to clear out
+ the upper bits. */
+ if (TYPE_LENGTH (to) < TYPE_LENGTH (from))
+ gen_extend (ax, from);
+
+ /* If the two values have equal width, but different signednesses,
+ then we need to extend. */
+ else if (TYPE_LENGTH (to) == TYPE_LENGTH (from))
+ {
+ if (TYPE_UNSIGNED (from) != TYPE_UNSIGNED (to))
+ gen_extend (ax, to);
+ }
+
+ /* If we're converting to a wider type, and becoming unsigned, then
+ we need to zero out any possible sign bits. */
+ else if (TYPE_LENGTH (to) > TYPE_LENGTH (from))
+ {
+ if (TYPE_UNSIGNED (to))
+ gen_extend (ax, to);
+ }
+}
+
+
+/* Return non-zero iff the type FROM will require any bytecodes to be
+ emitted to be converted to the type TO. */
+static int
+is_nontrivial_conversion (from, to)
+ struct type *from, *to;
+{
+ struct agent_expr *ax = new_agent_expr ();
+ int nontrivial;
+
+ /* Actually generate the code, and see if anything came out. At the
+ moment, it would be trivial to replicate the code in
+ gen_conversion here, but in the future, when we're supporting
+ floating point and the like, it may not be. Doing things this
+ way allows this function to be independent of the logic in
+ gen_conversion. */
+ gen_conversion (ax, from, to);
+ nontrivial = ax->len > 0;
+ free_agent_expr (ax);
+ return nontrivial;
+}
+
+
+/* Generate code to perform the "usual arithmetic conversions" (ANSI C
+ 6.2.1.5) for the two operands of an arithmetic operator. This
+ effectively finds a "least upper bound" type for the two arguments,
+ and promotes each argument to that type. *VALUE1 and *VALUE2
+ describe the values as they are passed in, and as they are left. */
+static void
+gen_usual_arithmetic (ax, value1, value2)
+ struct agent_expr *ax;
+ struct axs_value *value1, *value2;
+{
+ /* Do the usual binary conversions. */
+ if (TYPE_CODE (value1->type) == TYPE_CODE_INT
+ && TYPE_CODE (value2->type) == TYPE_CODE_INT)
+ {
+ /* The ANSI integral promotions seem to work this way: Order the
+ integer types by size, and then by signedness: an n-bit
+ unsigned type is considered "wider" than an n-bit signed
+ type. Promote to the "wider" of the two types, and always
+ promote at least to int. */
+ struct type *target = max_type (builtin_type_int,
+ max_type (value1->type, value2->type));
+
+ /* Deal with value2, on the top of the stack. */
+ gen_conversion (ax, value2->type, target);
+
+ /* Deal with value1, not on the top of the stack. Don't
+ generate the `swap' instructions if we're not actually going
+ to do anything. */
+ if (is_nontrivial_conversion (value1->type, target))
+ {
+ ax_simple (ax, aop_swap);
+ gen_conversion (ax, value1->type, target);
+ ax_simple (ax, aop_swap);
+ }
+
+ value1->type = value2->type = target;
+ }
+}
+
+
+/* Generate code to perform the integral promotions (ANSI 6.2.1.1) on
+ the value on the top of the stack, as described by VALUE. Assume
+ the value has integral type. */
+static void
+gen_integral_promotions (ax, value)
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ if (! type_wider_than (value->type, builtin_type_int))
+ {
+ gen_conversion (ax, value->type, builtin_type_int);
+ value->type = builtin_type_int;
+ }
+ else if (! type_wider_than (value->type, builtin_type_unsigned_int))
+ {
+ gen_conversion (ax, value->type, builtin_type_unsigned_int);
+ value->type = builtin_type_unsigned_int;
+ }
+}
+
+
+/* Generate code for a cast to TYPE. */
+static void
+gen_cast (ax, value, type)
+ struct agent_expr *ax;
+ struct axs_value *value;
+ struct type *type;
+{
+ /* GCC does allow casts to yield lvalues, so this should be fixed
+ before merging these changes into the trunk. */
+ require_rvalue (ax, value);
+ /* Dereference typedefs. */
+ type = check_typedef (type);
+
+ switch (type->code)
+ {
+ case TYPE_CODE_PTR:
+ /* It's implementation-defined, and I'll bet this is what GCC
+ does. */
+ break;
+
+ case TYPE_CODE_ARRAY:
+ case TYPE_CODE_STRUCT:
+ case TYPE_CODE_UNION:
+ case TYPE_CODE_FUNC:
+ error ("Illegal type cast: intended type must be scalar.");
+
+ case TYPE_CODE_ENUM:
+ /* We don't have to worry about the size of the value, because
+ all our integral values are fully sign-extended, and when
+ casting pointers we can do anything we like. Is there any
+ way for us to actually know what GCC actually does with a
+ cast like this? */
+ value->type = type;
+ break;
+
+ case TYPE_CODE_INT:
+ gen_conversion (ax, value->type, type);
+ break;
+
+ case TYPE_CODE_VOID:
+ /* We could pop the value, and rely on everyone else to check
+ the type and notice that this value doesn't occupy a stack
+ slot. But for now, leave the value on the stack, and
+ preserve the "value == stack element" assumption. */
+ break;
+
+ default:
+ error ("Casts to requested type are not yet implemented.");
+ }
+
+ value->type = type;
+}
+
+
+\f
+/* Generating bytecode from GDB expressions: arithmetic */
+
+/* Scale the integer on the top of the stack by the size of the target
+ of the pointer type TYPE. */
+static void
+gen_scale (ax, op, type)
+ struct agent_expr *ax;
+ enum agent_op op;
+ struct type *type;
+{
+ struct type *element = TYPE_TARGET_TYPE (type);
+
+ if (element->length != 1)
+ {
+ ax_const_l (ax, element->length);
+ ax_simple (ax, op);
+ }
+}
+
+
+/* Generate code for an addition; non-trivial because we deal with
+ pointer arithmetic. We set VALUE to describe the result value; we
+ assume VALUE1 and VALUE2 describe the two operands, and that
+ they've undergone the usual binary conversions. Used by both
+ BINOP_ADD and BINOP_SUBSCRIPT. NAME is used in error messages. */
+static void
+gen_add (ax, value, value1, value2, name)
+ struct agent_expr *ax;
+ struct axs_value *value, *value1, *value2;
+ char *name;
+{
+ /* Is it INT+PTR? */
+ if (value1->type->code == TYPE_CODE_INT
+ && value2->type->code == TYPE_CODE_PTR)
+ {
+ /* Swap the values and proceed normally. */
+ ax_simple (ax, aop_swap);
+ gen_scale (ax, aop_mul, value2->type);
+ ax_simple (ax, aop_add);
+ gen_extend (ax, value2->type); /* Catch overflow. */
+ value->type = value2->type;
+ }
+
+ /* Is it PTR+INT? */
+ else if (value1->type->code == TYPE_CODE_PTR
+ && value2->type->code == TYPE_CODE_INT)
+ {
+ gen_scale (ax, aop_mul, value1->type);
+ ax_simple (ax, aop_add);
+ gen_extend (ax, value1->type); /* Catch overflow. */
+ value->type = value1->type;
+ }
+
+ /* Must be number + number; the usual binary conversions will have
+ brought them both to the same width. */
+ else if (value1->type->code == TYPE_CODE_INT
+ && value2->type->code == TYPE_CODE_INT)
+ {
+ ax_simple (ax, aop_add);
+ gen_extend (ax, value1->type); /* Catch overflow. */
+ value->type = value1->type;
+ }
+
+ else
+ error ("Illegal combination of types in %s.", name);
+
+ value->kind = axs_rvalue;
+}
+
+
+/* Generate code for an addition; non-trivial because we have to deal
+ with pointer arithmetic. We set VALUE to describe the result
+ value; we assume VALUE1 and VALUE2 describe the two operands, and
+ that they've undergone the usual binary conversions. */
+static void
+gen_sub (ax, value, value1, value2)
+ struct agent_expr *ax;
+ struct axs_value *value, *value1, *value2;
+{
+ struct type *element;
+
+ if (value1->type->code == TYPE_CODE_PTR)
+ {
+ /* Is it PTR - INT? */
+ if (value2->type->code == TYPE_CODE_INT)
+ {
+ gen_scale (ax, aop_mul, value1->type);
+ ax_simple (ax, aop_sub);
+ gen_extend (ax, value1->type); /* Catch overflow. */
+ value->type = value1->type;
+ }
+
+ /* Is it PTR - PTR? Strictly speaking, the types ought to
+ match, but this is what the normal GDB expression evaluator
+ tests for. */
+ else if (value2->type->code == TYPE_CODE_PTR
+ && (TYPE_LENGTH (TYPE_TARGET_TYPE (value1->type))
+ == TYPE_LENGTH (TYPE_TARGET_TYPE (value2->type))))
+ {
+ ax_simple (ax, aop_sub);
+ gen_scale (ax, aop_div_unsigned, value1->type);
+ value->type = builtin_type_long; /* FIXME --- should be ptrdiff_t */
+ }
+ else
+ error ("\
+First argument of `-' is a pointer, but second argument is neither\n\
+an integer nor a pointer of the same type.");
+ }
+
+ /* Must be number + number. */
+ else if (value1->type->code == TYPE_CODE_INT
+ && value2->type->code == TYPE_CODE_INT)
+ {
+ ax_simple (ax, aop_sub);
+ gen_extend (ax, value1->type); /* Catch overflow. */
+ value->type = value1->type;
+ }
+
+ else
+ error ("Illegal combination of types in subtraction.");
+
+ value->kind = axs_rvalue;
+}
+
+/* Generate code for a binary operator that doesn't do pointer magic.
+ We set VALUE to describe the result value; we assume VALUE1 and
+ VALUE2 describe the two operands, and that they've undergone the
+ usual binary conversions. MAY_CARRY should be non-zero iff the
+ result needs to be extended. NAME is the English name of the
+ operator, used in error messages */
+static void
+gen_binop (ax, value, value1, value2, op, op_unsigned, may_carry, name)
+ struct agent_expr *ax;
+ struct axs_value *value, *value1, *value2;
+ enum agent_op op, op_unsigned;
+ int may_carry;
+ char *name;
+{
+ /* We only handle INT op INT. */
+ if ((value1->type->code != TYPE_CODE_INT)
+ || (value2->type->code != TYPE_CODE_INT))
+ error ("Illegal combination of types in %s.", name);
+
+ ax_simple (ax,
+ TYPE_UNSIGNED (value1->type) ? op_unsigned : op);
+ if (may_carry)
+ gen_extend (ax, value1->type); /* catch overflow */
+ value->type = value1->type;
+ value->kind = axs_rvalue;
+}
+
+
+static void
+gen_logical_not (ax, value)
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ if (TYPE_CODE (value->type) != TYPE_CODE_INT
+ && TYPE_CODE (value->type) != TYPE_CODE_PTR)
+ error ("Illegal type of operand to `!'.");
+
+ gen_usual_unary (ax, value);
+ ax_simple (ax, aop_log_not);
+ value->type = builtin_type_int;
+}
+
+
+static void
+gen_complement (ax, value)
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ if (TYPE_CODE (value->type) != TYPE_CODE_INT)
+ error ("Illegal type of operand to `~'.");
+
+ gen_usual_unary (ax, value);
+ gen_integral_promotions (ax, value);
+ ax_simple (ax, aop_bit_not);
+ gen_extend (ax, value->type);
+}
+
+
+\f
+/* Generating bytecode from GDB expressions: * & . -> @ sizeof */
+
+/* Dereference the value on the top of the stack. */
+static void
+gen_deref (ax, value)
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ /* The caller should check the type, because several operators use
+ this, and we don't know what error message to generate. */
+ if (value->type->code != TYPE_CODE_PTR)
+ error ("GDB bug: ax-gdb.c (gen_deref): expected a pointer");
+
+ /* We've got an rvalue now, which is a pointer. We want to yield an
+ lvalue, whose address is exactly that pointer. So we don't
+ actually emit any code; we just change the type from "Pointer to
+ T" to "T", and mark the value as an lvalue in memory. Leave it
+ to the consumer to actually dereference it. */
+ value->type = TYPE_TARGET_TYPE (value->type);
+ value->kind = ((value->type->code == TYPE_CODE_FUNC)
+ ? axs_rvalue : axs_lvalue_memory);
+}
+
+
+/* Produce the address of the lvalue on the top of the stack. */
+static void
+gen_address_of (ax, value)
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ /* Special case for taking the address of a function. The ANSI
+ standard describes this as a special case, too, so this
+ arrangement is not without motivation. */
+ if (value->type->code == TYPE_CODE_FUNC)
+ /* The value's already an rvalue on the stack, so we just need to
+ change the type. */
+ value->type = lookup_pointer_type (value->type);
+ else
+ switch (value->kind)
+ {
+ case axs_rvalue:
+ error ("Operand of `&' is an rvalue, which has no address.");
+
+ case axs_lvalue_register:
+ error ("Operand of `&' is in a register, and has no address.");
+
+ case axs_lvalue_memory:
+ value->kind = axs_rvalue;
+ value->type = lookup_pointer_type (value->type);
+ break;
+ }
+}
+
+
+/* A lot of this stuff will have to change to support C++. But we're
+ not going to deal with that at the moment. */
+
+/* Find the field in the structure type TYPE named NAME, and return
+ its index in TYPE's field array. */
+static int
+find_field (type, name)
+ struct type *type;
+ char *name;
+{
+ int i;
+
+ CHECK_TYPEDEF (type);
+
+ /* Make sure this isn't C++. */
+ if (TYPE_N_BASECLASSES (type) != 0)
+ error ("GDB bug: ax-gdb.c (find_field): derived classes supported");
+
+ for (i = 0; i < TYPE_NFIELDS (type); i++)
+ {
+ char *this_name = TYPE_FIELD_NAME (type, i);
+
+ if (this_name && STREQ (name, this_name))
+ return i;
+
+ if (this_name[0] == '\0')
+ error ("GDB bug: ax-gdb.c (find_field): anonymous unions not supported");
+ }
+
+ error ("Couldn't find member named `%s' in struct/union `%s'",
+ name, type->tag_name);
+
+ return 0;
+}
+
+
+/* Generate code to push the value of a bitfield of a structure whose
+ address is on the top of the stack. START and END give the
+ starting and one-past-ending *bit* numbers of the field within the
+ structure. */
+static void
+gen_bitfield_ref (ax, value, type, start, end)
+ struct agent_expr *ax;
+ struct axs_value *value;
+ struct type *type;
+ int start, end;
+{
+ /* Note that ops[i] fetches 8 << i bits. */
+ static enum agent_op ops[]
+ = { aop_ref8, aop_ref16, aop_ref32, aop_ref64 };
+ static int num_ops = (sizeof (ops) / sizeof (ops[0]));
+
+ /* We don't want to touch any byte that the bitfield doesn't
+ actually occupy; we shouldn't make any accesses we're not
+ explicitly permitted to. We rely here on the fact that the
+ bytecode `ref' operators work on unaligned addresses.
+
+ It takes some fancy footwork to get the stack to work the way
+ we'd like. Say we're retrieving a bitfield that requires three
+ fetches. Initially, the stack just contains the address:
+ addr
+ For the first fetch, we duplicate the address
+ addr addr
+ then add the byte offset, do the fetch, and shift and mask as
+ needed, yielding a fragment of the value, properly aligned for
+ the final bitwise or:
+ addr frag1
+ then we swap, and repeat the process:
+ frag1 addr --- address on top
+ frag1 addr addr --- duplicate it
+ frag1 addr frag2 --- get second fragment
+ frag1 frag2 addr --- swap again
+ frag1 frag2 frag3 --- get third fragment
+ Notice that, since the third fragment is the last one, we don't
+ bother duplicating the address this time. Now we have all the
+ fragments on the stack, and we can simply `or' them together,
+ yielding the final value of the bitfield. */
+
+ /* The first and one-after-last bits in the field, but rounded down
+ and up to byte boundaries. */
+ int bound_start = (start / TARGET_CHAR_BIT) * TARGET_CHAR_BIT;
+ int bound_end = (((end + TARGET_CHAR_BIT - 1)
+ / TARGET_CHAR_BIT)
+ * TARGET_CHAR_BIT);
+
+ /* current bit offset within the structure */
+ int offset;
+
+ /* The index in ops of the opcode we're considering. */
+ int op;
+
+ /* The number of fragments we generated in the process. Probably
+ equal to the number of `one' bits in bytesize, but who cares? */
+ int fragment_count;
+
+ /* Dereference any typedefs. */
+ type = check_typedef (type);
+
+ /* Can we fetch the number of bits requested at all? */
+ if ((end - start) > ((1 << num_ops) * 8))
+ error ("GDB bug: ax-gdb.c (gen_bitfield_ref): bitfield too wide");
+
+ /* Note that we know here that we only need to try each opcode once.
+ That may not be true on machines with weird byte sizes. */
+ offset = bound_start;
+ fragment_count = 0;
+ for (op = num_ops - 1; op >= 0; op--)
+ {
+ /* number of bits that ops[op] would fetch */
+ int op_size = 8 << op;
+
+ /* The stack at this point, from bottom to top, contains zero or
+ more fragments, then the address. */
+
+ /* Does this fetch fit within the bitfield? */
+ if (offset + op_size <= bound_end)
+ {
+ /* Is this the last fragment? */
+ int last_frag = (offset + op_size == bound_end);
+
+ if (! last_frag)
+ ax_simple (ax, aop_dup); /* keep a copy of the address */
+
+ /* Add the offset. */
+ gen_offset (ax, offset / TARGET_CHAR_BIT);
+
+ if (trace_kludge)
+ {
+ /* Record the area of memory we're about to fetch. */
+ ax_trace_quick (ax, op_size / TARGET_CHAR_BIT);
+ }
+
+ /* Perform the fetch. */
+ ax_simple (ax, ops[op]);
+
+ /* Shift the bits we have to their proper position.
+ gen_left_shift will generate right shifts when the operand
+ is negative.
+
+ A big-endian field diagram to ponder:
+ byte 0 byte 1 byte 2 byte 3 byte 4 byte 5 byte 6 byte 7
+ +------++------++------++------++------++------++------++------+
+ xxxxAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBCCCCCxxxxxxxxxxx
+ ^ ^ ^ ^
+ bit number 16 32 48 53
+ These are bit numbers as supplied by GDB. Note that the
+ bit numbers run from right to left once you've fetched the
+ value!
+
+ A little-endian field diagram to ponder:
+ byte 7 byte 6 byte 5 byte 4 byte 3 byte 2 byte 1 byte 0
+ +------++------++------++------++------++------++------++------+
+ xxxxxxxxxxxAAAAABBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCCCCCCCCCCCCCxxxx
+ ^ ^ ^ ^ ^
+ bit number 48 32 16 4 0
+
+ In both cases, the most significant end is on the left
+ (i.e. normal numeric writing order), which means that you
+ don't go crazy thinking about `left' and `right' shifts.
+
+ We don't have to worry about masking yet:
+ - If they contain garbage off the least significant end, then we
+ must be looking at the low end of the field, and the right
+ shift will wipe them out.
+ - If they contain garbage off the most significant end, then we
+ must be looking at the most significant end of the word, and
+ the sign/zero extension will wipe them out.
+ - If we're in the interior of the word, then there is no garbage
+ on either end, because the ref operators zero-extend. */
+ if (TARGET_BYTE_ORDER == BIG_ENDIAN)
+ gen_left_shift (ax, end - (offset + op_size));
+ else
+ gen_left_shift (ax, offset - start);
+
+ if (! last_frag)
+ /* Bring the copy of the address up to the top. */
+ ax_simple (ax, aop_swap);
+
+ offset += op_size;
+ fragment_count++;
+ }
+ }
+
+ /* Generate enough bitwise `or' operations to combine all the
+ fragments we left on the stack. */
+ while (fragment_count-- > 1)
+ ax_simple (ax, aop_bit_or);
+
+ /* Sign- or zero-extend the value as appropriate. */
+ ((TYPE_UNSIGNED (type) ? ax_zero_ext : ax_ext) (ax, end - start));
+
+ /* This is *not* an lvalue. Ugh. */
+ value->kind = axs_rvalue;
+ value->type = type;
+}
+
+
+/* Generate code to reference the member named FIELD of a structure or
+ union. The top of the stack, as described by VALUE, should have
+ type (pointer to a)* struct/union. OPERATOR_NAME is the name of
+ the operator being compiled, and OPERAND_NAME is the kind of thing
+ it operates on; we use them in error messages. */
+static void
+gen_struct_ref (ax, value, field, operator_name, operand_name)
+ struct agent_expr *ax;
+ struct axs_value *value;
+ char *field;
+ char *operator_name;
+ char *operand_name;
+{
+ struct type *type;
+ int i;
+
+ /* Follow pointers until we reach a non-pointer. These aren't the C
+ semantics, but they're what the normal GDB evaluator does, so we
+ should at least be consistent. */
+ while (value->type->code == TYPE_CODE_PTR)
+ {
+ gen_usual_unary (ax, value);
+ gen_deref (ax, value);
+ }
+ type = value->type;
+
+ /* This must yield a structure or a union. */
+ if (TYPE_CODE (type) != TYPE_CODE_STRUCT
+ && TYPE_CODE (type) != TYPE_CODE_UNION)
+ error ("The left operand of `%s' is not a %s.",
+ operator_name, operand_name);
+
+ /* And it must be in memory; we don't deal with structure rvalues,
+ or structures living in registers. */
+ if (value->kind != axs_lvalue_memory)
+ error ("Structure does not live in memory.");
+
+ i = find_field (type, field);
+
+ /* Is this a bitfield? */
+ if (TYPE_FIELD_PACKED (type, i))
+ gen_bitfield_ref (ax, value, TYPE_FIELD_TYPE (type, i),
+ TYPE_FIELD_BITPOS (type, i),
+ (TYPE_FIELD_BITPOS (type, i)
+ + TYPE_FIELD_BITSIZE (type, i)));
+ else
+ {
+ gen_offset (ax, TYPE_FIELD_BITPOS (type, i) / TARGET_CHAR_BIT);
+ value->kind = axs_lvalue_memory;
+ value->type = TYPE_FIELD_TYPE (type, i);
+ }
+}
+
+
+/* Generate code for GDB's magical `repeat' operator.
+ LVALUE @ INT creates an array INT elements long, and whose elements
+ have the same type as LVALUE, located in memory so that LVALUE is
+ its first element. For example, argv[0]@argc gives you the array
+ of command-line arguments.
+
+ Unfortunately, because we have to know the types before we actually
+ have a value for the expression, we can't implement this perfectly
+ without changing the type system, having values that occupy two
+ stack slots, doing weird things with sizeof, etc. So we require
+ the right operand to be a constant expression. */
+static void
+gen_repeat (pc, ax, value)
+ union exp_element **pc;
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ struct axs_value value1;
+ /* We don't want to turn this into an rvalue, so no conversions
+ here. */
+ gen_expr (pc, ax, &value1);
+ if (value1.kind != axs_lvalue_memory)
+ error ("Left operand of `@' must be an object in memory.");
+
+ /* Evaluate the length; it had better be a constant. */
+ {
+ struct value *v = const_expr (pc);
+ int length;
+
+ if (! v)
+ error ("Right operand of `@' must be a constant, in agent expressions.");
+ if (v->type->code != TYPE_CODE_INT)
+ error ("Right operand of `@' must be an integer.");
+ length = value_as_long (v);
+ if (length <= 0)
+ error ("Right operand of `@' must be positive.");
+
+ /* The top of the stack is already the address of the object, so
+ all we need to do is frob the type of the lvalue. */
+ {
+ /* FIXME-type-allocation: need a way to free this type when we are
+ done with it. */
+ struct type *range
+ = create_range_type (0, builtin_type_int, 0, length - 1);
+ struct type *array = create_array_type (0, value1.type, range);
+
+ value->kind = axs_lvalue_memory;
+ value->type = array;
+ }
+ }
+}
+
+
+/* Emit code for the `sizeof' operator.
+ *PC should point at the start of the operand expression; we advance it
+ to the first instruction after the operand. */
+static void
+gen_sizeof (pc, ax, value)
+ union exp_element **pc;
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ /* We don't care about the value of the operand expression; we only
+ care about its type. However, in the current arrangement, the
+ only way to find an expression's type is to generate code for it.
+ So we generate code for the operand, and then throw it away,
+ replacing it with code that simply pushes its size. */
+ int start = ax->len;
+ gen_expr (pc, ax, value);
+
+ /* Throw away the code we just generated. */
+ ax->len = start;
+
+ ax_const_l (ax, TYPE_LENGTH (value->type));
+ value->kind = axs_rvalue;
+ value->type = builtin_type_int;
+}
+
+\f
+/* Generating bytecode from GDB expressions: general recursive thingy */
+
+/* A gen_expr function written by a Gen-X'er guy.
+ Append code for the subexpression of EXPR starting at *POS_P to AX. */
+static void
+gen_expr (pc, ax, value)
+ union exp_element **pc;
+ struct agent_expr *ax;
+ struct axs_value *value;
+{
+ /* Used to hold the descriptions of operand expressions. */
+ struct axs_value value1, value2;
+ enum exp_opcode op = (*pc)[0].opcode;
+
+ /* If we're looking at a constant expression, just push its value. */
+ {
+ struct value *v = maybe_const_expr (pc);
+
+ if (v)
+ {
+ ax_const_l (ax, value_as_long (v));
+ value->kind = axs_rvalue;
+ value->type = check_typedef (VALUE_TYPE (v));
+ return;
+ }
+ }
+
+ /* Otherwise, go ahead and generate code for it. */
+ switch (op)
+ {
+ /* Binary arithmetic operators. */
+ case BINOP_ADD:
+ case BINOP_SUB:
+ case BINOP_MUL:
+ case BINOP_DIV:
+ case BINOP_REM:
+ case BINOP_SUBSCRIPT:
+ case BINOP_BITWISE_AND:
+ case BINOP_BITWISE_IOR:
+ case BINOP_BITWISE_XOR:
+ (*pc)++;
+ gen_expr (pc, ax, &value1);
+ gen_usual_unary (ax, &value1);
+ gen_expr (pc, ax, &value2);
+ gen_usual_unary (ax, &value2);
+ gen_usual_arithmetic (ax, &value1, &value2);
+ switch (op)
+ {
+ case BINOP_ADD:
+ gen_add (ax, value, &value1, &value2, "addition");
+ break;
+ case BINOP_SUB:
+ gen_sub (ax, value, &value1, &value2);
+ break;
+ case BINOP_MUL:
+ gen_binop (ax, value, &value1, &value2,
+ aop_mul, aop_mul, 1, "multiplication");
+ break;
+ case BINOP_DIV:
+ gen_binop (ax, value, &value1, &value2,
+ aop_div_signed, aop_div_unsigned, 1, "division");
+ break;
+ case BINOP_REM:
+ gen_binop (ax, value, &value1, &value2,
+ aop_rem_signed, aop_rem_unsigned, 1, "remainder");
+ break;
+ case BINOP_SUBSCRIPT:
+ gen_add (ax, value, &value1, &value2, "array subscripting");
+ if (TYPE_CODE (value->type) != TYPE_CODE_PTR)
+ error ("Illegal combination of types in array subscripting.");
+ gen_deref (ax, value);
+ break;
+ case BINOP_BITWISE_AND:
+ gen_binop (ax, value, &value1, &value2,
+ aop_bit_and, aop_bit_and, 0, "bitwise and");
+ break;
+
+ case BINOP_BITWISE_IOR:
+ gen_binop (ax, value, &value1, &value2,
+ aop_bit_or, aop_bit_or, 0, "bitwise or");
+ break;
+
+ case BINOP_BITWISE_XOR:
+ gen_binop (ax, value, &value1, &value2,
+ aop_bit_xor, aop_bit_xor, 0, "bitwise exclusive-or");
+ break;
+
+ default:
+ /* We should only list operators in the outer case statement
+ that we actually handle in the inner case statement. */
+ error ("GDB bug: ax-gdb.c (gen_expr): op case sets don't match");
+ }
+ break;
+
+ /* Note that we need to be a little subtle about generating code
+ for comma. In C, we can do some optimizations here because
+ we know the left operand is only being evaluated for effect.
+ However, if the tracing kludge is in effect, then we always
+ need to evaluate the left hand side fully, so that all the
+ variables it mentions get traced. */
+ case BINOP_COMMA:
+ (*pc)++;
+ gen_expr (pc, ax, &value1);
+ /* Don't just dispose of the left operand. We might be tracing,
+ in which case we want to emit code to trace it if it's an
+ lvalue. */
+ gen_traced_pop (ax, &value1);
+ gen_expr (pc, ax, value);
+ /* It's the consumer's responsibility to trace the right operand. */
+ break;
+
+ case OP_LONG: /* some integer constant */
+ {
+ struct type *type = (*pc)[1].type;
+ LONGEST k = (*pc)[2].longconst;
+ (*pc) += 4;
+ gen_int_literal (ax, value, k, type);
+ }
+ break;
+
+ case OP_VAR_VALUE:
+ gen_var_ref (ax, value, (*pc)[2].symbol);
+ (*pc) += 4;
+ break;
+
+ case OP_REGISTER:
+ {
+ int reg = (int) (*pc)[1].longconst;
+ (*pc) += 3;
+ value->kind = axs_lvalue_register;
+ value->u.reg = reg;
+ value->type = REGISTER_VIRTUAL_TYPE (reg);
+ }
+ break;
+
+ case OP_INTERNALVAR:
+ error ("GDB agent expressions cannot use convenience variables.");
+
+ /* Weirdo operator: see comments for gen_repeat for details. */
+ case BINOP_REPEAT:
+ /* Note that gen_repeat handles its own argument evaluation. */
+ (*pc)++;
+ gen_repeat (pc, ax, value);
+ break;
+
+ case UNOP_CAST:
+ {
+ struct type *type = (*pc)[1].type;
+ (*pc) += 3;
+ gen_expr (pc, ax, value);
+ gen_cast (ax, value, type);
+ }
+ break;
+
+ case UNOP_MEMVAL:
+ {
+ struct type *type = check_typedef ((*pc)[1].type);
+ (*pc) += 3;
+ gen_expr (pc, ax, value);
+ /* I'm not sure I understand UNOP_MEMVAL entirely. I think
+ it's just a hack for dealing with minsyms; you take some
+ integer constant, pretend it's the address of an lvalue of
+ the given type, and dereference it. */
+ if (value->kind != axs_rvalue)
+ /* This would be weird. */
+ error ("GDB bug: ax-gdb.c (gen_expr): OP_MEMVAL operand isn't an rvalue???");
+ value->type = type;
+ value->kind = axs_lvalue_memory;
+ }
+ break;
+
+ case UNOP_NEG:
+ (*pc)++;
+ /* -FOO is equivalent to 0 - FOO. */
+ gen_int_literal (ax, &value1, (LONGEST) 0, builtin_type_int);
+ gen_usual_unary (ax, &value1); /* shouldn't do much */
+ gen_expr (pc, ax, &value2);
+ gen_usual_unary (ax, &value2);
+ gen_usual_arithmetic (ax, &value1, &value2);
+ gen_sub (ax, value, &value1, &value2);
+ break;
+
+ case UNOP_LOGICAL_NOT:
+ (*pc)++;
+ gen_expr (pc, ax, value);
+ gen_logical_not (ax, value);
+ break;
+
+ case UNOP_COMPLEMENT:
+ (*pc)++;
+ gen_expr (pc, ax, value);
+ gen_complement (ax, value);
+ break;
+
+ case UNOP_IND:
+ (*pc)++;
+ gen_expr (pc, ax, value);
+ gen_usual_unary (ax, value);
+ if (TYPE_CODE (value->type) != TYPE_CODE_PTR)
+ error ("Argument of unary `*' is not a pointer.");
+ gen_deref (ax, value);
+ break;
+
+ case UNOP_ADDR:
+ (*pc)++;
+ gen_expr (pc, ax, value);
+ gen_address_of (ax, value);
+ break;
+
+ case UNOP_SIZEOF:
+ (*pc)++;
+ /* Notice that gen_sizeof handles its own operand, unlike most
+ of the other unary operator functions. This is because we
+ have to throw away the code we generate. */
+ gen_sizeof (pc, ax, value);
+ break;
+
+ case STRUCTOP_STRUCT:
+ case STRUCTOP_PTR:
+ {
+ int length = (*pc)[1].longconst;
+ char *name = &(*pc)[2].string;
+
+ (*pc) += 4 + BYTES_TO_EXP_ELEM (length + 1);
+ gen_expr (pc, ax, value);
+ if (op == STRUCTOP_STRUCT)
+ gen_struct_ref (ax, value, name, ".", "structure or union");
+ else if (op == STRUCTOP_PTR)
+ gen_struct_ref (ax, value, name, "->",
+ "pointer to a structure or union");
+ else
+ /* If this `if' chain doesn't handle it, then the case list
+ shouldn't mention it, and we shouldn't be here. */
+ error ("GDB bug: ax-gdb.c (gen_expr): unhandled struct case");
+ }
+ break;
+
+ case OP_TYPE:
+ error ("Attempt to use a type name as an expression.");
+
+ default:
+ error ("Unsupported operator in expression.");
+ }
+}
+
+
+\f
+/* Generating bytecode from GDB expressions: driver */
+
+/* Given a GDB expression EXPR, produce a string of agent bytecode
+ which computes its value. Return the agent expression, and set
+ *VALUE to describe its type, and whether it's an lvalue or rvalue. */
+struct agent_expr *
+expr_to_agent (expr, value)
+ struct expression *expr;
+ struct axs_value *value;
+{
+ struct cleanup *old_chain = 0;
+ struct agent_expr *ax = new_agent_expr ();
+ union exp_element *pc;
+
+ old_chain = make_cleanup (free_agent_expr, ax);
+
+ pc = expr->elts;
+ trace_kludge = 0;
+ gen_expr (&pc, ax, value);
+
+ /* We have successfully built the agent expr, so cancel the cleanup
+ request. If we add more cleanups that we always want done, this
+ will have to get more complicated. */
+ discard_cleanups (old_chain);
+ return ax;
+}
+
+
+/* Given a GDB expression EXPR denoting an lvalue in memory, produce a
+ string of agent bytecode which will leave its address and size on
+ the top of stack. Return the agent expression.
+
+ Not sure this function is useful at all. */
+struct agent_expr *
+expr_to_address_and_size (expr)
+ struct expression *expr;
+{
+ struct axs_value value;
+ struct agent_expr *ax = expr_to_agent (expr, &value);
+
+ /* Complain if the result is not a memory lvalue. */
+ if (value.kind != axs_lvalue_memory)
+ {
+ free_agent_expr (ax);
+ error ("Expression does not denote an object in memory.");
+ }
+
+ /* Push the object's size on the stack. */
+ ax_const_l (ax, TYPE_LENGTH (value.type));
+
+ return ax;
+}
+
+
+/* Given a GDB expression EXPR, return bytecode to trace its value.
+ The result will use the `trace' and `trace_quick' bytecodes to
+ record the value of all memory touched by the expression. The
+ caller can then use the ax_reqs function to discover which
+ registers it relies upon. */
+struct agent_expr *
+gen_trace_for_expr (expr)
+ struct expression *expr;
+{
+ struct cleanup *old_chain = 0;
+ struct agent_expr *ax = new_agent_expr ();
+ union exp_element *pc;
+ struct axs_value value;
+
+ old_chain = make_cleanup (free_agent_expr, ax);
+
+ pc = expr->elts;
+ trace_kludge = 1;
+ gen_expr (&pc, ax, &value);
+
+ /* Make sure we record the final object, and get rid of it. */
+ gen_traced_pop (ax, &value);
+
+ /* Oh, and terminate. */
+ ax_simple (ax, aop_end);
+
+ /* We have successfully built the agent expr, so cancel the cleanup
+ request. If we add more cleanups that we always want done, this
+ will have to get more complicated. */
+ discard_cleanups (old_chain);
+ return ax;
+}
+
+
+\f
+/* The "agent" command, for testing: compile and disassemble an expression. */
+
+static void
+print_axs_value (f, value)
+ GDB_FILE *f;
+ struct axs_value *value;
+{
+ switch (value->kind)
+ {
+ case axs_rvalue:
+ fputs_filtered ("rvalue", f);
+ break;
+
+ case axs_lvalue_memory:
+ fputs_filtered ("memory lvalue", f);
+ break;
+
+ case axs_lvalue_register:
+ fprintf_filtered (f, "register %d lvalue", value->u.reg);
+ break;
+ }
+
+ fputs_filtered (" : ", f);
+ type_print (value->type, "", f, -1);
+}
+
+
+static void
+agent_command (exp, from_tty)
+ char *exp;
+ int from_tty;
+{
+ struct cleanup *old_chain = 0;
+ struct expression *expr;
+ struct agent_expr *agent;
+ struct agent_reqs reqs;
+
+ /* We don't deal with overlay debugging at the moment. We need to
+ think more carefully about this. If you copy this code into
+ another command, change the error message; the user shouldn't
+ have to know anything about agent expressions. */
+ if (overlay_debugging)
+ error ("GDB can't do agent expression translation with overlays.");
+
+ if (exp == 0)
+ error_no_arg ("expression to translate");
+
+ expr = parse_expression (exp);
+ old_chain = make_cleanup (free_current_contents, &expr);
+ agent = gen_trace_for_expr (expr);
+ make_cleanup (free_agent_expr, agent);
+ ax_print (gdb_stdout, agent);
+ ax_reqs (agent, &reqs);
+
+ do_cleanups (old_chain);
+ dont_repeat ();
+}
+
+\f
+/* Initialization code. */
+
+_initialize_ax_gdb ()
+{
+ struct cmd_list_element *c;
+
+ add_cmd ("agent", class_maintenance, agent_command,
+ "Translate an expression into remote agent bytecode.",
+ &maintenancelist);
+}
projects / binutils-gdb.git / commitdiff