jcf-write.c

gcc-2.95.3 Linux下最常用的C编译器

/* Generate bytecode for sub-expression EXP of METHOD.
   TARGET is one of STACK_TARGET or IGNORE_TARGET. */

static void
generate_bytecode_insns (exp, target, state)
     tree exp;
     int target;
     struct jcf_partial *state;
{
  tree type;
  enum java_opcode jopcode;
  int op;
  HOST_WIDE_INT value;
  int post_op;
  int size;
  int offset;

  if (exp == NULL && target == IGNORE_TARGET)
    return;

  type = TREE_TYPE (exp);

  switch (TREE_CODE (exp))
    {
    case BLOCK:
      if (BLOCK_EXPR_BODY (exp))
	{
	  tree local;
	  tree body = BLOCK_EXPR_BODY (exp);
	  for (local = BLOCK_EXPR_DECLS (exp); local; )
	    {
	      tree next = TREE_CHAIN (local);
	      localvar_alloc (local, state);
	      local = next;
	    }
	  /* Avoid deep recursion for long blocks. */
	  while (TREE_CODE (body) == COMPOUND_EXPR)
	    {
	      generate_bytecode_insns (TREE_OPERAND (body, 0), target, state);
	      body = TREE_OPERAND (body, 1);
	    }
	  generate_bytecode_insns (body, target, state);
	  for (local = BLOCK_EXPR_DECLS (exp); local; )
	    {
	      tree next = TREE_CHAIN (local);
	      localvar_free (local, state);
	      local = next;
	    }
	}
      break;
      case COMPOUND_EXPR:	
	generate_bytecode_insns (TREE_OPERAND (exp, 0), IGNORE_TARGET, state);
	generate_bytecode_insns (TREE_OPERAND (exp, 1), target, state);
      break;
    case EXPR_WITH_FILE_LOCATION:
      {
	char *saved_input_filename = input_filename;
	tree body = EXPR_WFL_NODE (exp);
	int saved_lineno = lineno;
	if (body == empty_stmt_node)
	  break;
	input_filename = EXPR_WFL_FILENAME (exp);
	lineno = EXPR_WFL_LINENO (exp);
	if (EXPR_WFL_EMIT_LINE_NOTE (exp) && lineno > 0
	    && debug_info_level > DINFO_LEVEL_NONE)
	  put_linenumber (lineno, state);
	generate_bytecode_insns (body, target, state);
	input_filename = saved_input_filename;
	lineno = saved_lineno;
      }
      break;
    case INTEGER_CST:
      if (target == IGNORE_TARGET) ; /* do nothing */
      else if (TREE_CODE (type) == POINTER_TYPE)
	{
	  if (! integer_zerop (exp))
	    abort();
	  RESERVE(1);
	  OP1 (OPCODE_aconst_null);
	  NOTE_PUSH (1);
	}
      else if (TYPE_PRECISION (type) <= 32)
	{
	  push_int_const (TREE_INT_CST_LOW (exp), state);
	  NOTE_PUSH (1);
	}
      else
	{
	  push_long_const (TREE_INT_CST_LOW (exp), TREE_INT_CST_HIGH (exp),
			   state);
	  NOTE_PUSH (2);
	}
      break;
    case REAL_CST:
      {
	int prec = TYPE_PRECISION (type) >> 5;
	RESERVE(1);
	if (real_zerop (exp))
	  OP1 (prec == 1 ? OPCODE_fconst_0 : OPCODE_dconst_0);
	else if (real_onep (exp))
	  OP1 (prec == 1 ? OPCODE_fconst_1 : OPCODE_dconst_1);
	/* FIXME Should also use fconst_2 for 2.0f.
	   Also, should use iconst_2/ldc followed by i2f/i2d
	   for other float/double when the value is a small integer. */
	else
	  {
	    offset = find_constant_index (exp, state);
	    if (prec == 1)
	      push_constant1 (offset, state);
	    else
	      push_constant2 (offset, state);
	  }
	NOTE_PUSH (prec);
      }
      break;
    case STRING_CST:
      push_constant1 (find_string_constant (&state->cpool, exp), state);
      NOTE_PUSH (1);
      break;
    case VAR_DECL:
      if (TREE_STATIC (exp))
	{
	  field_op (exp, OPCODE_getstatic, state);
	  NOTE_PUSH (TYPE_IS_WIDE (TREE_TYPE (exp)) ? 2 : 1);
	  break;
	}
      /* ... fall through ... */
    case PARM_DECL:
      emit_load (exp, state);
      break;
    case NON_LVALUE_EXPR:
    case INDIRECT_REF:
      generate_bytecode_insns (TREE_OPERAND (exp, 0), target, state);
      break;
    case ARRAY_REF:
      generate_bytecode_insns (TREE_OPERAND (exp, 0), target, state);
      generate_bytecode_insns (TREE_OPERAND (exp, 1), target, state);
      if (target != IGNORE_TARGET)
	{
	  jopcode = OPCODE_iaload + adjust_typed_op (type, 7);
	  RESERVE(1);
	  OP1 (jopcode);
	  if (! TYPE_IS_WIDE (type))
	    NOTE_POP (1);
	}
      break;
    case COMPONENT_REF:
      {
	tree obj = TREE_OPERAND (exp, 0);
	tree field = TREE_OPERAND (exp, 1);
	int is_static = FIELD_STATIC (field);
	generate_bytecode_insns (obj,
				 is_static ? IGNORE_TARGET : target, state);
	if (target != IGNORE_TARGET)
	  {
	    if (DECL_NAME (field) == length_identifier_node && !is_static
		&& TYPE_ARRAY_P (TREE_TYPE (obj)))
	      {
		RESERVE (1);
		OP1 (OPCODE_arraylength);
	      }
	    else
	      {
		field_op (field, is_static ? OPCODE_getstatic : OPCODE_getfield,
			  state);
		if (! is_static)
		  NOTE_POP (1);
		NOTE_PUSH (TYPE_IS_WIDE (TREE_TYPE (field)) ? 2 : 1);
	      }
	  }
      }
      break;
    case TRUTH_ANDIF_EXPR:
    case TRUTH_ORIF_EXPR:
    case EQ_EXPR:
    case NE_EXPR:
    case GT_EXPR:
    case LT_EXPR:
    case GE_EXPR:
    case LE_EXPR:
      {
	struct jcf_block *then_label = gen_jcf_label (state);
	struct jcf_block *else_label = gen_jcf_label (state);
	struct jcf_block *end_label = gen_jcf_label (state);
	generate_bytecode_conditional (exp,
				       then_label, else_label, 1, state);
	define_jcf_label (then_label, state);
	push_int_const (1, state);
	emit_goto (end_label, state);
	define_jcf_label (else_label, state);
	push_int_const (0, state);
	define_jcf_label (end_label, state);
	NOTE_PUSH (1);
      }
      break;
    case COND_EXPR:
      {
	struct jcf_block *then_label = gen_jcf_label (state);
	struct jcf_block *else_label = gen_jcf_label (state);
	struct jcf_block *end_label = gen_jcf_label (state);
	generate_bytecode_conditional (TREE_OPERAND (exp, 0),
				       then_label, else_label, 1, state);
	define_jcf_label (then_label, state);
	generate_bytecode_insns (TREE_OPERAND (exp, 1), target, state);
	if (CAN_COMPLETE_NORMALLY (TREE_OPERAND (exp, 1))
	    /* Not all expressions have CAN_COMPLETE_NORMALLY set properly. */
	    || TREE_CODE (TREE_TYPE (exp)) != VOID_TYPE)
	  emit_goto (end_label, state);
	define_jcf_label (else_label, state);
	generate_bytecode_insns (TREE_OPERAND (exp, 2), target, state);
	define_jcf_label (end_label, state);
      }
      break;
    case CASE_EXPR:
      {
	struct jcf_switch_state *sw_state = state->sw_state;
	struct jcf_relocation *reloc = (struct jcf_relocation *)
	  obstack_alloc (state->chunk_obstack, sizeof (struct jcf_relocation));
	HOST_WIDE_INT case_value = TREE_INT_CST_LOW (TREE_OPERAND (exp, 0));
	reloc->kind = 0;
	reloc->label = get_jcf_label_here (state);
	reloc->offset = case_value;
	reloc->next = sw_state->cases;
	sw_state->cases = reloc;
	if (sw_state->num_cases == 0)
	  {
	    sw_state->min_case = case_value;
	    sw_state->max_case = case_value;
	  }
	else
	  {
	    if (case_value < sw_state->min_case)
	      sw_state->min_case = case_value;
	    if (case_value > sw_state->max_case)
	      sw_state->max_case = case_value;
	  }
	sw_state->num_cases++;
      }
      break;
    case DEFAULT_EXPR:
      state->sw_state->default_label = get_jcf_label_here (state);
      break;

    case SWITCH_EXPR:
      {
	/* The SWITCH_EXPR has three parts, generated in the following order:
	   1.  the switch_expression (the value used to select the correct case);
	   2.  the switch_body;
	   3.  the switch_instruction (the tableswitch/loopupswitch instruction.).
	   After code generation, we will re-order then in the order 1, 3, 2.
	   This is to avoid an extra GOTOs. */
	struct jcf_switch_state sw_state;
	struct jcf_block *expression_last; /* Last block of the switch_expression. */
	struct jcf_block *body_last; /* Last block of the switch_body. */
	struct jcf_block *switch_instruction;  /* First block of switch_instruction. */
	struct jcf_block *instruction_last; /* Last block of the switch_instruction. */
	struct jcf_block *body_block;
	int switch_length;
	sw_state.prev = state->sw_state;
	state->sw_state = &sw_state;
	sw_state.cases = NULL;
	sw_state.num_cases = 0;
	sw_state.default_label = NULL;
	generate_bytecode_insns (TREE_OPERAND (exp, 0), STACK_TARGET, state);
	expression_last = state->last_block;
	body_block = get_jcf_label_here (state);  /* Force a new block here. */
	generate_bytecode_insns (TREE_OPERAND (exp, 1), IGNORE_TARGET, state);
	body_last = state->last_block;

	switch_instruction = gen_jcf_label (state);
	define_jcf_label (switch_instruction, state);
	if (sw_state.default_label == NULL)
	  sw_state.default_label = gen_jcf_label (state);

	if (sw_state.num_cases <= 1)
	  {
	    if (sw_state.num_cases == 0)
	      {
		emit_pop (1, state);
		NOTE_POP (1);
	      }
	    else
	      {
		push_int_const (sw_state.cases->offset, state);
		emit_if (sw_state.cases->label,
			 OPCODE_ifeq, OPCODE_ifne, state);
	      }
	    emit_goto (sw_state.default_label, state);
	  }
	else
	  {
	    HOST_WIDE_INT i;
	    /* Copy the chain of relocs into a sorted array. */
	    struct jcf_relocation **relocs = (struct jcf_relocation **)
	      xmalloc (sw_state.num_cases * sizeof (struct jcf_relocation *));
	    /* The relocs arrays is a buffer with a gap.
	       The assumption is that cases will normally come in "runs". */
	    int gap_start = 0;
	    int gap_end = sw_state.num_cases;
	    struct jcf_relocation *reloc;
	    for (reloc = sw_state.cases;  reloc != NULL;  reloc = reloc->next)
	      {
		HOST_WIDE_INT case_value = reloc->offset;
		while (gap_end < sw_state.num_cases)
		  {
		    struct jcf_relocation *end = relocs[gap_end];
		    if (case_value <= end->offset)
		      break;
		    relocs[gap_start++] = end;
		    gap_end++;
		  }
		while (gap_start > 0)
		  {
		    struct jcf_relocation *before = relocs[gap_start-1];
		    if (case_value >= before->offset)
		      break;
		    relocs[--gap_end] = before;
		    gap_start--;
		  }
		relocs[gap_start++] = reloc;
		/* Note we don't check for duplicates.  FIXME! */
	      }

	    if (2 * sw_state.num_cases
		>= sw_state.max_case - sw_state.min_case)
	      { /* Use tableswitch. */
		int index = 0;
		RESERVE (13 + 4 * (sw_state.max_case - sw_state.min_case + 1));
		OP1 (OPCODE_tableswitch);
		emit_reloc (0, SWITCH_ALIGN_RELOC, NULL, state);
		emit_switch_reloc (sw_state.default_label, state);
		OP4 (sw_state.min_case);
		OP4 (sw_state.max_case);
		for (i = sw_state.min_case; ; )
		  {
		    reloc = relocs[index];
		    if (i == reloc->offset)
		      {
			emit_case_reloc (reloc, state);
			if (i == sw_state.max_case)
			  break;
			index++;
		      }
		    else
		      emit_switch_reloc (sw_state.default_label, state);
		    i++;
		  }
	      }
	    else
	      { /* Use lookupswitch. */
		RESERVE(9 + 8 * sw_state.num_cases);
		OP1 (OPCODE_lookupswitch);
		emit_reloc (0, SWITCH_ALIGN_RELOC, NULL, state);
		emit_switch_reloc (sw_state.default_label, state);
		OP4 (sw_state.num_cases);
		for (i = 0;  i < sw_state.num_cases;  i++)
		  {
		    struct jcf_relocation *reloc = relocs[i];
		    OP4 (reloc->offset);
		    emit_case_reloc (reloc, state);
		  }
	      }
	    free (relocs);
	  }

	instruction_last = state->last_block;
	if (sw_state.default_label->pc < 0)
	  define_jcf_label (sw_state.default_label, state);
	else /* Force a new block. */
	  sw_state.default_label = get_jcf_label_here (state);
	/* Now re-arrange the blocks so the switch_instruction
	   comes before the switch_body. */
	switch_length = state->code_length - switch_instruction->pc;
	switch_instruction->pc = body_block->pc;
	instruction_last->next = body_block;
	instruction_last->v.chunk->next = body_block->v.chunk;
	expression_last->next = switch_instruction;
	expression_last->v.chunk->next = switch_instruction->v.chunk;
	body_last->next = sw_state.default_label;
	body_last->v.chunk->next = NULL;
	state->chunk = body_last->v.chunk;
	for (;  body_block != sw_state.default_label;  body_block = body_block->next)
	  body_block->pc += switch_length;

	state->sw_state = sw_state.prev;
	break;
      }

    case RETURN_EXPR:
      exp = TREE_OPERAND (exp, 0);
      if (exp == NULL_TREE)
	exp = empty_stmt_node;
      else if (TREE_CODE (exp) != MODIFY_EXPR) 
	abort ();
      else
	exp = TREE_OPERAND (exp, 1);
      generate_bytecode_return (exp, state);
      break;
    case LABELED_BLOCK_EXPR:
      {
	struct jcf_block *end_label = gen_jcf_label (state);
	end_label->next = state->labeled_blocks;
	state->labeled_blocks = end_label;
	end_label->pc = PENDING_EXIT_PC;
	end_label->u.labeled_block = exp;
	if (LABELED_BLOCK_BODY (exp))
	  generate_bytecode_insns (LABELED_BLOCK_BODY (exp), target, state);
	if (state->labeled_blocks != end_label)
	  abort();
	state->labeled_blocks = end_label->next;
	define_jcf_label (end_label, state);
      }
      break;
    case LOOP_EXPR:
      {
	tree body = TREE_OPERAND (exp, 0);
#if 0
	if (TREE_CODE (body) == COMPOUND_EXPR
	    && TREE_CODE (TREE_OPERAND (body, 0)) == EXIT_EXPR)
	  {
	    /* Optimize:  H: if (TEST) GOTO L; BODY; GOTO H; L:
	       to:  GOTO L;  BODY;  L:  if (!TEST) GOTO L; */
	    struct jcf_block *head_label;
	    struct jcf_block *body_label;
	    struct jcf_block *end_label = gen_jcf_label (state);
	    struct jcf_block *exit_label = state->labeled_blocks;
	    head_label = gen_jcf_label (state);
	    emit_goto (head_label, state);
	    body_label = get_jcf_label_here (state);
	    generate_bytecode_insns (TREE_OPERAND (body, 1), target, state);
	    define_jcf_label (head_label, state);
	    generate_bytecode_conditional (TREE_OPERAND (body, 0),
					   end_label, body_label, 1, state);
	    define_jcf_label (end_label, state);
	  }
	else
#endif
	  {
	    struct jcf_block *head_label = get_jcf_label_here (state);
	    generate_bytecode_insns (body, IGNORE_TARGET, state);
	    emit_goto (head_label, state);
	  }
      }
      break;
    case EXIT_EXPR:
      {
	struct jcf_block *label = state->labeled_blocks;
	struct jcf_block *end_label = gen_jcf_label (state);
	generate_bytecode_conditional (TREE_OPERAND (exp, 0),
				       label, end_label, 0, state);
	define_jcf_label (end_label, state);
      }
      break;