Clang defaults to an x86_64 triple on Windows ARM64

[jakepetroules]

$ echo %PROCESSOR_ARCHITECTURE%
ARM64

$ clang -v
clang version 19.1.4
Target: x86_64-unknown-windows-msvc
Thread model: posix
InstalledDir: C:\Users\jakepetroules\AppData\Local\Programs\Swift\Toolchains\6.1.0+Asserts\usr\bin
Build config: +assertions

This seems wrong. I would expect the default triple to be aarch64-unknown-windows-msvc, just like swiftc.

[compnerd]

Can you link to the installer that was used? The x64 toolchain should/will default to x64 on arm64. Only the arm64 toolchain will default to arm64.

[jakepetroules]

This was an x64 toolchain. If that's the expected behavior, this can be closed. However, swiftc defaults to aarch64 even with the x64 toolchain, which seems inconsistent.

[compnerd]

That does seem inconsistent, I would expect that the swift toolchain defaults to x86_64 there as well. This might be something we need to change in swift-driver (CC: @artemcm)

[jroelofs]

Clang's default triple is configurable at build time, so if anything, this is an issue with the build script used to build the clang that comes with that toolchain.