On Sun, 2006-06-04 at 22:01, Rask Ingemann Lambertsen wrote: > On Sun, Jun 04, 2006 at 12:24:53PM +0100, Paul Brook wrote: > > > For the record these hacks are unlikely to ever be acceptable in mainline > > gcc. > > They're relatively invasive changes who's only purpose is to support > > fundamentally broken hardware. > > We don't yet know if they'll be invasive. There's a good chance that they > won't be more than a few new insn patterns, a secondary output reload > to provide a scratch register and a pair of new options. > I'm confident right now that these will be too invasive to include in mainline.
> There are other targets with targets specific options to work around this or > that bug, quirk, defect or errata. In this case, why would two options > -mno-byte-writes and -mbyte-writes, with the latter being the default, be > unlikely to be acceptable? In particular, the MT port has these two options: The changes that tend to get incorporated into the compiler are to work around bugs in the CPU, not bugs in some H/W developer's use of the CPU. The former affect all users of the processor, the latter only that one case. If we started putting in hacks for the latter the compiler back-ends would become unmaintainable in almost no time at all. Sorry, it's just not going to happen. R. PS. Using swp is a bad idea IMO, this instruction is *very* slow on some CPU implementations because of the way it interacts with caches. It certainly isn't suitable as a generic solution to this sort of issue.
