compiler-builtins: Enable AArch64 __chkstk for MinGW

[mati865]

Similarly to i686 and X86_64 MinGW targets, Rust needs to provide the right chkstk symbol for AArch64 to avoid relying on the linker to provide it.

CC rust-lang/rust#150725

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[tgross35]

Just to cross reference, does LLVM compiler-rt and/or libgcc provide this?

[mati865]

Yeah, they do. LLVM code might be hard to read without proficiency, so posting symbol dump instead:

$ nm -A /g/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-* | rg chkstk
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-aarch64.a:chkstk.S.obj: 00000000 T #__chkstk_arm64ec
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-aarch64.a:chkstk.S.obj: 00000000 T __chkstk
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-arm.a:chkstk.S.obj: 00000000 T __chkstk
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-i386.a:chkstk.S.obj: 00000000 T __alloca
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-x86_64.a:chkstk.S.obj: 00000000 T ___chkstk_ms

GCC support for AArch64 is experimental, so I didn't bother finding toolchain to check it.

[tgross35]

Thank you!

[mati865]

Thanks. May I ask when typically the builtins subtree is synced to the main repo?

[tgross35]

It's in progress, just had to wait on CI 👍

[mati865]

Oh, no worries. I was just curious how long it takes.