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I’m trying to make swiftc build for the ‘xtensa’ architecture (ESP32).

It appears that the latest nightly snapshot (from march 7th) is aware of the ‘xtensa’ architecture, which I understand that LLVM supports from release 16. Or at least I get a different error message when using the latest public release of swift 5.10 and the nightly snapshot.

But I cannot make swiftc accept a target triple like ‘xtensa-none-none-eabi’.

Is there any place I could find a list of supported triples?

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You can start with clang, which could be a first approximation for what architectures LLVM used in swiftc supports: clang -print-targets.

I'm not aware of a flag that makes swiftc print all available triples. An unknown triple that can be parsed in the embedded mode will trigger error output listing available embedded triples:

❯ touch test.swift
❯ swiftc -enable-experimental-feature Embedded \
  -wmo test.swift \
  -target m68k-none-none-eabi
<unknown>:0: error: could not find module 'Swift' for target 'm68k-none-none-eabi'; found: 
riscv32-none-none-eabi, x86_64-unknown-windows-coff, riscv64-none-none-eabi, i686-unknown-none-elf, armv7-apple-none-macho, armv6m-none-none-eabi, aarch64-none-none-elf, wasm64-unknown-none-wasm, arm64-apple-macos, x86_64-unknown-none-elf, arm64-apple-none-macho, armv7-none-none-eabi, armv7em-none-none-eabi, arm64e-apple-macos, x86_64-apple-macos, i686-unknown-windows-coff, armv6-apple-none-macho, armv6m-apple-none-macho, wasm32-unknown-none-wasm, armv7em-apple-none-macho, armv6-none-none-eabi, at: ~/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2024-03-07-a.xctoolchain/usr/lib/swift/embedded/Swift.swiftmodule

Another indicator is triple parsing code in Swift Driver, it doesn't have any mentions of xtensa: swift-driver/Sources/SwiftDriver/Utilities/Triple.swift at main · apple/swift-driver · GitHub

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Thank you, @Max_Desiatov ! :blush:

I saw a post about xtensa support in llvm 16 and thought that I might be lucky that it was supported in Swift:

I found an ESP32 developer board in a drawer and hoped to be able to play around with getting Swift up and running for it. :grin: Without otherwise knowing what that would entail… :grimacing:

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It is worth noting that ESP32 comes in two flavors: riscv32 and xtensa. I don't think xtensa targets are supported yet in the llvm/clang swift uses (yet). The last time I looked at it there was a decent amount of work to do for getting that merged in, but maybe now that merge has occurred it is a bit less.

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The xtensa backend is WIP https://github.com/espressif/llvm-project

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