Re: [avr-gcc-list] >4.5.1 better than this at register-structure (xmega) access?

[Erik Walthinsen]

On 10/10/2012 02:24 PM, Weddington, Eric wrote:
> But as you said: Does it do that with recent versions? I'm afraid that no one 
> yet knows.

Nope: (stock binutils 2.22, gcc 4.72, avr-libc 1.80)

void structwrite(uint8_t v) {
  TCC0.CTRLE = v;
 a58:   e0 e0           ldi     r30, 0x00       ; 0
 a5a:   f8 e0           ldi     r31, 0x08       ; 8
 a5c:   84 83           std     Z+4, r24        ; 0x04
 a5e:   08 95           ret
}

void straightwrite(uint8_t v) {
  TCC0_CTRLE = v;
 a60:   80 93 04 08     sts     0x0804, r24
 a64:   08 95           ret
}

#define FS(s,m) (*(typeof(s.m) *)((void *)&s + offsetof(typeof(s),m)))
void macrowrite(uint8_t v) {
  FS(TCC0,CTRLE) = v;
 a66:   80 93 04 08     sts     0x0804, r24
 a6a:   08 95           ret
}

(both -O2 and -O6 produce the same, compiled with -fno-inline)