This is arbitrary since spirv (as opposed to spirv32/spirv64) refers to the
version with logical memory layout, i.e. no 'real' pointers. This change at
least matches what clang does.
It is impossible to even build projects like glibc when targeting a generic
SPARC v8 CPU; LEON3 is effectively considered the baseline for `sparc-linux-gnu`
now, particularly due to it supporting a CASA instruction similar to the one in
SPARC v9. However, it's slightly incompatible with SPARC v9 due to having a
different ASI tag, so resulting binaries would not be portable to regular SPARC
CPUs. So, as the least bad option, make v9 the baseline for sparc32.
* Rename isPPC() -> isPowerPC32().
* Rename isPPC64() -> isPowerPC64().
* Add new isPowerPC() function which covers both.
There was confusion even in the standard library about what isPPC() meant. This
change makes these functions work how I think most people actually expect them
to work, and makes them consistent with isMIPS(), isSPARC(), etc.
I chose to rename from PPC to PowerPC because 1) it's more consistent with the
other functions, and 2) it'll cause loud rather than silent breakage for anyone
who might have been depending on isPPC() while misunderstanding it.
This is a fairly small hobby OS that has not seen development in 2 years. Our
current policy is that hobby OSs should use the `other` tag.
https://github.com/zhmu/ananas
What is `sparcel`, you might ask? Good question!
If you take a peek in the SPARC v8 manual, §2.2, it is quite explicit that SPARC
v8 is a big-endian architecture. No little-endian or mixed-endian support to be
found here.
On the other hand, the SPARC v9 manual, in §3.2.1.2, states that it has support
for mixed-endian operation, with big-endian mode being the default.
Ok, so `sparcel` must just be referring to SPARC v9 running in little-endian
mode, surely?
Nope:
* https://github.com/llvm/llvm-project/blob/40b4fd7a3e81d32b29364a1b15337bcf817659c0/llvm/lib/Target/Sparc/SparcTargetMachine.cpp#L226
* https://github.com/llvm/llvm-project/blob/40b4fd7a3e81d32b29364a1b15337bcf817659c0/llvm/lib/Target/Sparc/SparcTargetMachine.cpp#L104
So, `sparcel` in LLVM is referring to some sort of fantastical little-endian
SPARC v8 architecture. I've scoured the internet and I can find absolutely no
evidence that such a thing exists or has ever existed. In fact, I can find no
evidence that a little-endian implementation of SPARC v9 ever existed, either.
Or any SPARC version, actually!
The support was added here: https://reviews.llvm.org/D8741
Notably, there is no mention whatsoever of what CPU this might be referring to,
and no justification given for the "but some are little" comment added in the
patch.
My best guess is that this might have been some private exercise in creating a
little-endian version of SPARC that never saw the light of day. Given that SPARC
v8 explicitly doesn't support little-endian operation (let alone little-endian
instruction encoding!), and no CPU is known to be implemented as such, I think
it's very reasonable for us to just remove this support.
Andrew Kelley