stmt.c

这是完整的gcc源代码

	{
	  error ("output operand constraint lacks `='");
	  return;
	}

      /* If an output operand is not a variable or indirect ref,
	 or a part of one,
	 create a SAVE_EXPR which is a pseudo-reg
	 to act as an intermediate temporary.
	 Make the asm insn write into that, then copy it to
	 the real output operand.  */

      val1 = val;
      while (TREE_CODE (val1) == COMPONENT_REF
	     || TREE_CODE (val1) == ARRAY_REF)
	val1 = TREE_OPERAND (val1, 0);

      if (TREE_CODE (val1) != VAR_DECL
	  && TREE_CODE (val1) != PARM_DECL
	  && TREE_CODE (val1) != INDIRECT_REF)
	{
	  rtx reg = gen_reg_rtx (TYPE_MODE (TREE_TYPE (val)));
	  /* `build' isn't safe; it really expects args to be trees.  */
	  tree t = build_nt (SAVE_EXPR, val, reg);

	  if (GET_MODE (reg) == BLKmode)
	    abort ();

	  save_expr_regs = gen_rtx (EXPR_LIST, VOIDmode, reg, save_expr_regs);
	  TREE_VALUE (tail) = t;
	  TREE_TYPE (t) = TREE_TYPE (val);
	}
      output_rtx[i] = expand_expr (TREE_VALUE (tail), 0, VOIDmode, 0);
    }

  if (ninputs + noutputs > MAX_RECOG_OPERANDS)
    {
      error ("more than %d operands in `asm'", MAX_RECOG_OPERANDS);
      return;
    }

  /* Make vectors for the expression-rtx and constraint strings.  */

  argvec = rtvec_alloc (ninputs);
  constraints = rtvec_alloc (ninputs);

  body = gen_rtx (ASM_OPERANDS, VOIDmode,
		  TREE_STRING_POINTER (string), "", 0, argvec, constraints,
		  filename, line);
  MEM_VOLATILE_P (body) = vol;

  /* Eval the inputs and put them into ARGVEC.
     Put their constraints into ASM_INPUTs and store in CONSTRAINTS.  */

  i = 0;
  for (tail = inputs; tail; tail = TREE_CHAIN (tail))
    {
      int j;

      /* If there's an erroneous arg, emit no insn,
	 because the ASM_INPUT would get VOIDmode
	 and that could cause a crash in reload.  */
      if (TREE_TYPE (TREE_VALUE (tail)) == error_mark_node)
	return;
      if (TREE_PURPOSE (tail) == NULL_TREE)
	{
	  error ("hard register `%s' listed as input operand to `asm'",
		 TREE_STRING_POINTER (TREE_VALUE (tail)) );
	  return;
	}

      /* Make sure constraint has neither `=' nor `+'.  */

      for (j = 0; j < TREE_STRING_LENGTH (TREE_PURPOSE (tail)); j++)
	if (TREE_STRING_POINTER (TREE_PURPOSE (tail))[j] == '='
	    || TREE_STRING_POINTER (TREE_PURPOSE (tail))[j] == '+')
	  {
	    error ("input operand constraint contains `%c'",
		   TREE_STRING_POINTER (TREE_PURPOSE (tail))[j]);
	    return;
	  }

      XVECEXP (body, 3, i)      /* argvec */
	= expand_expr (TREE_VALUE (tail), 0, VOIDmode, 0);
      XVECEXP (body, 4, i)      /* constraints */
	= gen_rtx (ASM_INPUT, TYPE_MODE (TREE_TYPE (TREE_VALUE (tail))),
		   TREE_STRING_POINTER (TREE_PURPOSE (tail)));
      i++;
    }

  /* Protect all the operands from the queue,
     now that they have all been evaluated.  */

  for (i = 0; i < ninputs; i++)
    XVECEXP (body, 3, i) = protect_from_queue (XVECEXP (body, 3, i), 0);

  for (i = 0; i < noutputs; i++)
    output_rtx[i] = protect_from_queue (output_rtx[i], 1);

  /* Now, for each output, construct an rtx
     (set OUTPUT (asm_operands INSN OUTPUTNUMBER OUTPUTCONSTRAINT
			       ARGVEC CONSTRAINTS))
     If there is more than one, put them inside a PARALLEL.  */

  if (noutputs == 1 && nclobbers == 0)
    {
      XSTR (body, 1) = TREE_STRING_POINTER (TREE_PURPOSE (outputs));
      insn = emit_insn (gen_rtx (SET, VOIDmode, output_rtx[0], body));
    }
  else if (noutputs == 0 && nclobbers == 0)
    {
      /* No output operands: put in a raw ASM_OPERANDS rtx.  */
      insn = emit_insn (body);
    }
  else
    {
      rtx obody = body;
      int num = noutputs;
      if (num == 0) num = 1;
      body = gen_rtx (PARALLEL, VOIDmode, rtvec_alloc (num + nclobbers));

      /* For each output operand, store a SET.  */

      for (i = 0, tail = outputs; tail; tail = TREE_CHAIN (tail), i++)
	{
	  XVECEXP (body, 0, i)
	    = gen_rtx (SET, VOIDmode,
		       output_rtx[i],
		       gen_rtx (ASM_OPERANDS, VOIDmode,
				TREE_STRING_POINTER (string),
				TREE_STRING_POINTER (TREE_PURPOSE (tail)),
				i, argvec, constraints,
				filename, line));
	  MEM_VOLATILE_P (SET_SRC (XVECEXP (body, 0, i))) = vol;
	}

      /* If there are no outputs (but there are some clobbers)
	 store the bare ASM_OPERANDS into the PARALLEL.  */

      if (i == 0)
	XVECEXP (body, 0, i++) = obody;

      /* Store (clobber REG) for each clobbered register specified.  */

      for (tail = clobbers; tail; tail = TREE_CHAIN (tail), i++)
	{
	  int j;
	  char *regname = TREE_STRING_POINTER (TREE_VALUE (tail));
	  extern char *reg_names[];
	      
	  for (j = 0; j < FIRST_PSEUDO_REGISTER; j++)
	    if (!strcmp (regname, reg_names[j]))
	      break;
	      
	  if (j == FIRST_PSEUDO_REGISTER)
	    {
	      error ("unknown register name `%s' in `asm'", regname);
	      return;
	    }

	  /* Use QImode since that's guaranteed to clobber just one reg.  */
	  XVECEXP (body, 0, i)
	    = gen_rtx (CLOBBER, VOIDmode, gen_rtx (REG, QImode, j));
	}

      insn = emit_insn (body);
    }

  last_expr_type = 0;
}

/* Nonzero if within a ({...}) grouping, in which case we must
   always compute a value for each expr-stmt in case it is the last one.  */

int expr_stmts_for_value;

/* Generate RTL to evaluate the expression EXP
   and remember it in case this is the VALUE in a ({... VALUE; }) constr.  */

void
expand_expr_stmt (exp)
     tree exp;
{
  /* If -W, warn about statements with no side effects,
     except inside a ({...}) where they may be useful.  */
  if (expr_stmts_for_value == 0 && exp != error_mark_node)
    {
      if (! TREE_VOLATILE (exp) && (extra_warnings || warn_unused))
	warning_with_file_and_line (emit_filename, emit_lineno,
				    "statement with no effect");
      else if (warn_unused)
	warn_if_unused_value (exp);
    }
  last_expr_type = TREE_TYPE (exp);
  if (! flag_syntax_only)
    last_expr_value = expand_expr (exp, expr_stmts_for_value ? 0 : const0_rtx,
				   VOIDmode, 0);
  emit_queue ();
}

/* Warn if EXP contains any computations whose results are not used.
   Return 1 if a warning is printed; 0 otherwise.  */

static int
warn_if_unused_value (exp)
     tree exp;
{
  switch (TREE_CODE (exp))
    {
    case PREINCREMENT_EXPR:
    case POSTINCREMENT_EXPR:
    case PREDECREMENT_EXPR:
    case POSTDECREMENT_EXPR:
    case MODIFY_EXPR:
    case INIT_EXPR:
    case NEW_EXPR:
    case DELETE_EXPR:
    case PUSH_EXPR:
    case POP_EXPR:
    case CALL_EXPR:
    case METHOD_CALL_EXPR:
    case RTL_EXPR:
    case WRAPPER_EXPR:
    case ANTI_WRAPPER_EXPR:
    case WITH_CLEANUP_EXPR:
      /* We don't warn about COND_EXPR because it may be a useful
	 construct if either arm contains a side effect.  */
    case COND_EXPR:
      return 0;

    case TRUTH_ORIF_EXPR:
    case TRUTH_ANDIF_EXPR:
      /* In && or ||, warn if 2nd operand has no side effect.  */
      return warn_if_unused_value (TREE_OPERAND (exp, 1));

    case COMPOUND_EXPR:
      if (warn_if_unused_value (TREE_OPERAND (exp, 0)))
	return 1;
      return warn_if_unused_value (TREE_OPERAND (exp, 1));

    case NOP_EXPR:
    case CONVERT_EXPR:
      /* Don't warn about values cast to void.  */
      if (TREE_TYPE (exp) == void_type_node)
	return 0;
      /* Assignment to a cast results in a cast of a modify.
	 Don't complain about that.  */
      if (TREE_CODE (TREE_OPERAND (exp, 0)) == MODIFY_EXPR)
	return 0;

    default:
      warning_with_file_and_line (emit_filename, emit_lineno,
				  "value computed is not used");
      return 1;
    }
}

/* Clear out the memory of the last expression evaluated.  */

void
clear_last_expr ()
{
  last_expr_type = 0;
}

/* Begin a statement which will return a value.
   Return the RTL_EXPR for this statement expr.
   The caller must save that value and pass it to expand_end_stmt_expr.  */

tree
expand_start_stmt_expr ()
{
  rtx save = start_sequence ();
  /* Make the RTL_EXPR node temporary, not momentary,
     so that rtl_expr_chain doesn't become garbage.  */
  int momentary = suspend_momentary ();
  tree t = make_node (RTL_EXPR);
  resume_momentary (momentary);
  RTL_EXPR_RTL (t) = save;
  NO_DEFER_POP;
  expr_stmts_for_value++;
  return t;
}

/* Restore the previous state at the end of a statement that returns a value.
   Returns a tree node representing the statement's value and the
   insns to compute the value.

   The nodes of that expression have been freed by now, so we cannot use them.
   But we don't want to do that anyway; the expression has already been
   evaluated and now we just want to use the value.  So generate a RTL_EXPR
   with the proper type and RTL value.

   If the last substatement was not an expression,
   return something with type `void'.  */

tree
expand_end_stmt_expr (t)
     tree t;
{
  rtx saved = RTL_EXPR_RTL (t);

  emit_queue ();

  OK_DEFER_POP;

  if (last_expr_type == 0)
    {
      last_expr_type = void_type_node;
      last_expr_value = const0_rtx;
    }
  else if (last_expr_value == 0)
    /* There are some cases where this can happen, such as when the
       statement is void type.  */
    last_expr_value = const0_rtx;
  else
    last_expr_value = protect_from_queue (last_expr_value, 0);

  TREE_TYPE (t) = last_expr_type;
  RTL_EXPR_RTL (t) = last_expr_value;
  RTL_EXPR_SEQUENCE (t) = get_insns ();

  rtl_expr_chain = tree_cons (NULL_TREE, t, rtl_expr_chain);

  end_sequence (saved);

  /* Don't consider deleting this expr or containing exprs at tree level.  */
  TREE_VOLATILE (t) = 1;
  /* Propagate volatility of the actual RTL expr.  */
  TREE_THIS_VOLATILE (t) = volatile_refs_p (last_expr_value);

  last_expr_type = 0;
  expr_stmts_for_value--;

  return t;
}

/* Generate RTL for the start of an if-then.  COND is the expression
   whose truth should be tested.

   If EXITFLAG is nonzero, this conditional is visible to
   `exit_something'.  */

void
expand_start_cond (cond, exitflag)
     tree cond;
     int exitflag;
{
  struct nesting *thiscond
    = (struct nesting *) xmalloc (sizeof (struct nesting));

  /* Make an entry on cond_stack for the cond we are entering.  */

  thiscond->next = cond_stack;
  thiscond->all = nesting_stack;
  thiscond->depth = ++nesting_depth;
  thiscond->data.cond.after_label = 0;
  thiscond->data.cond.else_label = gen_label_rtx ();
  thiscond->exit_label = exitflag ? thiscond->data.cond.else_label : 0;
  cond_stack = thiscond;
  nesting_stack = thiscond;

  do_jump (cond, thiscond->data.cond.else_label, NULL);
}

/* Generate RTL for the end of an if-then with no else-clause.
   Pop the record for it off of cond_stack.  */

void
expand_end_cond ()
{
  struct nesting *thiscond = cond_stack;

  do_pending_stack_adjust ();
  emit_label (thiscond->data.cond.else_label);

  POPSTACK (cond_stack);
  last_expr_type = 0;
}

/* Generate RTL between the then-clause and the else-clause
   of an if-then-else.  */

void
expand_start_else ()
{
  cond_stack->data.cond.after_label = gen_label_rtx ();
  if (cond_stack->exit_label != 0)
    cond_stack->exit_label = cond_stack->data.cond.after_label;
  emit_jump (cond_stack->data.cond.after_label);
  if (cond_stack->data.cond.else_label)
    emit_label (cond_stack->data.cond.else_label);
}

/* Generate RTL for the end of an if-then-else.
   Pop the record for it off of cond_stack.  */

void
expand_end_else ()
{
  struct nesting *thiscond = cond_stack;

  do_pending_stack_adjust ();
  /* Note: a syntax error can cause this to be called
     without first calling `expand_start_else'.  */
  if (thiscond->data.cond.after_label)
    emit_label (thiscond->data.cond.after_label);

  POPSTACK (cond_stack);
  last_expr_type = 0;
}

/* Generate RTL for the start of a loop.  EXIT_FLAG is nonzero if this
   loop should be exited by `exit_something'.  This is a loop for which
   `expand_continue' will jump to the top of the loop.