This is the mail archive of the
cgen@sources.redhat.com
mailing list for the CGEN project.
Re: [Bug] subword handling for DI modes
Ben Elliston writes:
> While I don't have a fix for this problem, let me make the observation
> that the interpretation of the subword number (the last argument) is
> pretty iffy. Some cgen code interprets it an endian-dependent manner
> (as in "0th subword as laid out in memory"), and some other code in
> endian-independent (as in "0th among least->most significant
> subwords").
>
> I think the manual describes this predicament.
It does.
IIRC (but I wouldn't bet the farm on it) the rules follow gcc's SUBREG.
> I think the endinan-independent interpretation is more useful, but to
> switch over to it would require a fair bit of testing. Still, it's
> important to fix this one way or the other.
>
> I agree -- my preferred usage is for (subword <mode> 0) to give me bits 0 to
> sizeof(mode) - 1. I hope it can be fixed soon.