Re: Inefficient code

[Eric Botcazou <ebotcazou at adacore dot com>]

> I just constructed another test case that shows the same issue more
> blatantly:
> 
> struct s
> {
>     char a;
>     char b;
>     char c;
>     char d;
>     int e;
>     int f;
>     char h;
>     char i;
> };

No, it's not the same issue.

> struct s ts;
> 
> void setts(void)
> {
>     ts.a=2;
>     ts.b=4;
>     ts.c=1;
>     ts.d=24;
>     ts.e=5;
>     ts.f=42;
>     ts.h=9;
>     ts.i=3;
> }
> 
> Each of the fields are written separately, even though clearly the adjacent
> byte writes can and should be combined into a single HImode move.  This
> happens both with -O2 and -Os.

The GIMPLE pass responsible for the optimization simply punts for the "funny-
endian ordering" of the PDP11.  More generally, you shouldn't expect anything 
sparkling for such a peculiar architecture as the PDP11.

-- 
Eric Botcazou