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Re: SPE configuration in GCC
David Edelsohn wrote:
As Aldy mentioned, there already is a powerpc-linuxspe
configuration that seems to do what your customer wants.
gcc/config/rs6000/linuxspe.h makes the options active and defaults to a
8540 scheduling model, but does not enable the SPE features by default.
I don't think that's quite true. It seems to default to enabling SPE
via SUBTARGET_OVERRIDE_OIPTIONS. It also passes "-mspe -me500" to the
assembler unconditionally. Our customer wants SPE to be an option, not
I am wliling to consider a patch to rs6000.h and the other
headers, but I am not sure what benefit it provides over the
configurations that Aldy already designed and implemented.
I think that the best solution, then, is probably a new configuration
header for this customer. That's easy enough to arrange. We've
certainly established that the current situation is a conscious choice,
which was my primary objective.
As a secondary issue, it would be nice to have a GCC-wide policy about
whether "target-elf" should support all variants of a chip, or just
some. Based on my knowledge of users, I'd suggest that it should
support all variants.
As another secondary issue, I consider it a bug in the PowerPC back end
that command-line options (like -misel) are silently ignored in the
default configuration. If you agree, I can file a PR about that.