Re: [PATCH 4/8] Implement target_emit_ops

[Yao Qi <qiyaoltc at gmail dot com>]

Antoine Tremblay <antoine.tremblay@ericsson.com> writes:

>   I'm wondering is there a reason we don't use gcc to generate the
> native bytecode like done on x86 ?
>
> x86 has a macro like so :
>
> #define EMIT_ASM(NAME, INSNS)						
>   do									
>     {									
>       extern unsigned char start_ ## NAME, end_ ## NAME;		
>       add_insns (&start_ ## NAME, &end_ ## NAME - &start_ ## NAME);	
>       __asm__ ("jmp end_" #NAME "\n"					
> 	       "\t" "start_" #NAME ":"					
> 	       "\t" INSNS "\n"						
> 	       "\t" "end_" #NAME ":");					
>     } while (0)
>

The reason is about the code readability.  We find the way we are using
in aarch64 is more readable than the way for x86.

  p += emit_stp (p, x0, x1, sp, preindex_memory_operand (-2 * 16));
  p += emit_str (p, lr, sp, offset_memory_operand (3 * 8));
  p += emit_str (p, fp, sp, offset_memory_operand (2 * 8));
  p += emit_add (p, fp, sp, immediate_operand (2 * 8));

vs.

  EMIT_ASM (amd64_prologue,
            "pushq %rbp\n\t"
            "movq %rsp,%rbp\n\t"
            "sub $0x20,%rsp\n\t"
            "movq %rdi,-8(%rbp)\n\t"
            "movq %rsi,-16(%rbp)");

> Could the same be done for armv7 or there's a reason that prevents it ?
>

No reason prevents it, but the code should be readable.

-- 
Yao (éå)