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64-bit big endian PowerPC ABIv2 support #12667

Merged
merged 4 commits into from
Oct 16, 2023
Merged

64-bit big endian PowerPC ABIv2 support #12667

merged 4 commits into from
Oct 16, 2023

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awilfox
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@awilfox awilfox commented Oct 16, 2023

Passes on: Linux gwyn.foxkit.us 5.15.98-mc4-easy #1 SMP Sun Apr 2 00:16:18 CDT 2023 ppc64 GNU/Linux

Summary:
  3457 tests passed
   74 tests skipped
    0 tests failed
  137 tests not started (parent test skipped or failed)
    0 unexpected errors
  3668 tests considered

Fixes: #12656

@awilfox
Update POWER asmgen test for OCaml 5
f1ca080 
This updates the asmgen code the same way the runtime assembler was
updated in 05d82f9.
@awilfox
Support native compiler on ABIv2 Power BE (ocaml#12656)
13355e6 
This will only work on ABIv2 systems, such as Linux on musl libc and
FreeBSD/OpenBSD.  Tested on musl libc system and all tests pass.
dustanddreams
dustanddreams approved these changes Oct 16, 2023
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Verified to not cause any regression building and running the compiler testsuite on powerpc64le.

xavierleroy
xavierleroy approved these changes Oct 16, 2023
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Nice to see that the ELFv2 ABI works equally well in big-endian than in little-endian. Thanks! This is good to go, but the configure script may need to be hardened later to check that the ABI is actually ELFv2.

configure.ac
@@ -1262,6 +1262,8 @@ AS_CASE([$host],
[arch=amd64; system=win64],
[[powerpc64le*-*-linux*]],
[has_native_backend=yes; arch=power; model=ppc64le; system=linux],
[[powerpc64*-*-linux-musl*]],
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I'm assuming that given the history of Musl on Power, this implies that the ELFv2 ABI is used.

I wish config.guess was more explicit about which version of the ABI is used. E.g. on Ubuntu 16.04 PPC (the last Ubuntu to support big-endian PPC, using the ELFv1 ABI), config.guess reports powerpc64-unknown-linux-gnu, which does not obviously imply that it's ELFv1 and not ELFv2.

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The v2 ABI requires the preprocessor symbol _CALL_ELF to be defined with a value of 2. Some autoconf machinery could check for this and only enable native code on v2.

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Right. For the time being, I just added a check on _CALL_ELF in runtime/power.S, to abort in case of ABI mismatch. We'll see later if this needs to be done in configure.

@xavierleroy xavierleroy mentioned this pull request Oct 16, 2023
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@xavierleroy xavierleroy merged commit 82a04cf into ocaml:trunk Oct 16, 2023
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Thank you, @awilfox.

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@xavierleroy xavierleroy xavierleroy approved these changes

@dustanddreams dustanddreams dustanddreams approved these changes

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Support native compilation on big-endian ppc64
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@awilfox @sideeffect42 @xavierleroy @dustanddreams