`powerpc64-unknown-freebsd` version in ports has patches to ELF version support and target description

[estebank]

The packaged version of rust in FreeBSD patches their release with

--- compiler/rustc_target/src/abi/call/powerpc64.rs.orig    2020-03-09 22:11:17 UTC
+++ compiler/rustc_target/src/abi/call/powerpc64.rs
@@ -123,7 +123,7 @@ where
         ELFv2
     } else {
         match cx.data_layout().endian {
-            Endian::Big => ELFv1,
+            Endian::Big => ELFv2,
             Endian::Little => ELFv2,
         }
     };

https://cgit.freebsd.org/ports/tree/lang/rust/files/patch-compiler_rustc__target_src_abi_call_powerpc64.rs

Immediately before that we have the following:

    let abi = if cx.target_spec().env == "musl" {
        ELFv2
    } else {

We can add yet another check for them there so that powerpc64-unknown-freebsd always uses ELFv2. The platform list page shows this one as "PPC64 FreeBSD (ELFv1 and ELFv2)" on Tier 3.

I do not know if doing this change would cause other issues, maybe with lowest FreeBSD version support?

They've been carrying this patch since 2019.

---

https://github.com/freebsd/freebsd-ports/blob/9c64647054c81b8876c7f4f987189427b5858ad6/lang/rust/files/patch-compiler_rustc__target_src_spec_powerpc64__unknown__freebsd.rs#L1-L14

Since 2020.

[awilfox]

I noticed this while I was working on #128579. Technically, at least per LLVM, this should only be the case in FreeBSD >=13.

  /// Tests whether the target 64-bit PowerPC big endian ABI is ELFv2.
  bool isPPC64ELFv2ABI() const {
    return (getArch() == Triple::ppc64 &&
            ((getOS() == Triple::FreeBSD &&
              (getOSMajorVersion() >= 13 || getOSVersion().empty())) ||
             getOS() == Triple::OpenBSD || isMusl()));
  }

It also appears to be the ABI of choice for OpenBSD on both endians, though I'm not sure how well OpenBSD supports big endian 64-bit Power.