[mercury-users] Is -O0 actually necessary on MacOS X with gcc-4.0?

[Julien Fischer]

On Sun, 19 Aug 2007, Michael Day wrote:

> Hi Julien,
>
>> For low-level C grades**, yes.  For the hlc grades, (most probably) no.
>> 
>> Julien.
>> 
>> ** Actually only those low-level grades that use gcc global register 
>> variables.
>
> So that means asm_fast.gc, basically?

And reg.gc.  IIRC, the problems that required to the use of 
EXTRA_CFLAGS=-O0 with gcc 4 were mainly to do with some gcc optimizations 
interacting badly with global register vars.  (They were subsequently
fixed in gcc 4.1.)

> Mercury doesn't seem to support asm_fast.gc on MacOS X at all, regardless of 
> whether it's PowerPC or Intel and which gcc version is in use; I don't quite 
> understand why this is.

For the PowerPC version we could never get it to work (I could probably
have provided a more detailed answer two or so years ago, but I've
forgotten a lot of the details.)

For Intel macs, I'm not sure - I don't have access to one.

Julien.
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