gcc源代码分析，expand_call ()函数第四部分，emit_call_1 ()函数

本文是为了解释下面这4个rtx是如何产生的，和emit_call_1 ()函数有关。

(const_int 4)

(mem:QI (symbol_ref/v:SI ("printf")))

(call (mem:QI (symbol_ref/v:SI ("printf")))

   (const_int 4))

(set (reg:SI 0)

   (call (mem:QI (symbol_ref/v:SI ("printf")))

       (const_int 4)))

下面是加了fprintf()函数之后的调试结果。

(const_int 4)

emit_call_1 funexp symbol_ref

before emit_call_insn

(mem:QI (symbol_ref/v:SI ("printf")))

(call (mem:QI (symbol_ref/v:SI ("printf")))

   (const_int 4))

(set (reg:SI 0)

   (call (mem:QI (symbol_ref/v:SI ("printf")))

       (const_int 4)))

emit_call_insn

after emit_call_inst

after emit_call_1

end expand_call

expand_call ()函数中的相关代码：

  if (args_size.constant < 0)

    args_size.constant = 0;

  emit_call_1 (funexp, funtype, args_size.constant,

           FUNCTION_ARG (args_so_far, VOIDmode, void_type_node, 1),

           valreg, old_inhibit_defer_pop, use_insns);

/* ???  Nothing has been done here to record control flow

   when contained functions can do nonlocal gotos.  */

static void

emit_call_1 (funexp, funtype, stack_size, next_arg_reg, valreg, old_inhibit_defer_pop, use_insns)

     rtx funexp;

     tree funtype;

     int stack_size;

     rtx next_arg_reg;

     rtx valreg;

     int old_inhibit_defer_pop;

     rtx use_insns;

{

  rtx stack_size_rtx = gen_rtx (CONST_INT, VOIDmode, stack_size);

  rtx call_insn;

  if (valreg)

    emit_call_insn (gen_call_value (valreg,

                    gen_rtx (MEM, FUNCTION_MODE, funexp),

                    stack_size_rtx, next_arg_reg));

gen_call_value ()函数在insn-emit.c文件中和

(call (mem:QI (symbol_ref/v:SI ("printf")))

   (const_int 4))

(set (reg:SI 0)

   (call (mem:QI (symbol_ref/v:SI ("printf")))

       (const_int 4)))

这2个rtx有关。

rtx

gen_call_value (operand0, operand1, operand2)

     rtx operand0;

     rtx operand1;

     rtx operand2;

{

  return gen_rtx (SET, VOIDmode, operand0,
gen_rtx (CALL, VOIDmode, operand1, operand2));

}