Improve support for completely unknown architectures #10107
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This commit is a step in the direction of trying to make Wasmtime more portable by default. The goal here is to enable Wasmtime to compile for architectures that it has no prior knowledge of. There's a few miscellaneous locations through Wasmtime where we need architecture-specific intrinsics and such but that's all in service of Cranelift itself. Without Cranelift support none of them are necessary. This commit plumbs a custom `#[cfg]` from Wasmtime's `build.rs` script into the crate about whether there's a supported Cranelift backend. If this isn't available some architecture-specific intrinsics are turned off and not included. An example is that `vm::arch` entirely disappears which is only in service of `UnwindHost`, which also disappears. Furthermore the `helpers.c` file also entirely disappears as it's not necessary on unknown architectures. To help keep this working I've added CI to build Wasmtime for `powerpc64le-unknown-linux-gnu`. Wasmtime currently has no support for this architecture, although if it grows such support in the future this'll need to be changed to some other unsupported architecture.
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| // When Cranelift has support for the host then we might be running native | ||
| // compiled code meaning we need to read the actual stack pointer. If | ||
| // Cranelift can't be used though then we're guaranteed to be running pulley | ||
| // in which case this stack poitner isn't actually used as Pulley has custom | ||
| // mechanisms for stack overflow. | ||
| #[cfg(has_cranelift_host_backend)] |
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Can we rename this has_host_compiler_backend? While we don't have any target supported on Winch but not Cranelift now, it doesn't seem like it would be impossible in the future, so we should just try to be a little more precise about what we are saying.
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This commit is a step in the direction of trying to make Wasmtime more portable by default. The goal here is to enable Wasmtime to compile for architectures that it has no prior knowledge of. There's a few miscellaneous locations through Wasmtime where we need architecture-specific intrinsics and such but that's all in service of Cranelift itself. Without Cranelift support none of them are necessary.
This commit plumbs a custom
#[cfg]from Wasmtime'sbuild.rsscript into the crate about whether there's a supported Cranelift backend. If this isn't available some architecture-specific intrinsics are turned off and not included. An example is thatvm::archentirely disappears which is only in service ofUnwindHost, which also disappears. Furthermore thehelpers.cfile also entirely disappears as it's not necessary on unknown architectures.To help keep this working I've added CI to build Wasmtime for
powerpc64le-unknown-linux-gnu. Wasmtime currently has no support for this architecture, although if it grows such support in the future this'll need to be changed to some other unsupported architecture.