This commit refactors how the path to the linker that we're going to invoke is
selected. Previously all targets listed *both* a `LinkerFlavor` and a `linker`
(path) option, but this meant that whenever you changed one you had to change
the other. The purpose of this commit is to avoid coupling these where possible.
Target specifications now only unconditionally define the *flavor* of the linker
that they're using by default. If not otherwise specified each flavor now
implies a particular default linker to run. As a result, this means that if
you'd like to test out `ld` for example you should be able to do:
rustc -Z linker-flavor=ld foo.rs
whereas previously you had to do
rustc -Z linker-flavor=ld -C linker=ld foo.rs
This will hopefully make it a bit easier to tinker around with variants that
should otherwise be well known to work, for example with LLD, `ld` on OSX, etc.
This commit imports the LLD project from LLVM to serve as the default linker for
the `wasm32-unknown-unknown` target. The `binaryen` submoule is consequently
removed along with "binaryen linker" support in rustc.
Moving to LLD brings with it a number of benefits for wasm code:
* LLD is itself an actual linker, so there's no need to compile all wasm code
with LTO any more. As a result builds should be *much* speedier as LTO is no
longer forcibly enabled for all builds of the wasm target.
* LLD is quickly becoming an "official solution" for linking wasm code together.
This, I believe at least, is intended to be the main supported linker for
native code and wasm moving forward. Picking up support early on should help
ensure that we can help LLD identify bugs and otherwise prove that it works
great for all our use cases!
* Improvements to the wasm toolchain are currently primarily focused around LLVM
and LLD (from what I can tell at least), so it's in general much better to be
on this bandwagon for bugfixes and new features.
* Historical "hacks" like `wasm-gc` will soon no longer be necessary, LLD
will [natively implement][gc] `--gc-sections` (better than `wasm-gc`!) which
means a postprocessor is no longer needed to show off Rust's "small wasm
binary size".
LLD is added in a pretty standard way to rustc right now. A new rustbuild target
was defined for building LLD, and this is executed when a compiler's sysroot is
being assembled. LLD is compiled against the LLVM that we've got in tree, which
means we're currently on the `release_60` branch, but this may get upgraded in
the near future!
LLD is placed into rustc's sysroot in a `bin` directory. This is similar to
where `gcc.exe` can be found on Windows. This directory is automatically added
to `PATH` whenever rustc executes the linker, allowing us to define a `WasmLd`
linker which implements the interface that `wasm-ld`, LLD's frontend, expects.
Like Emscripten the LLD target is currently only enabled for Tier 1 platforms,
notably OSX/Windows/Linux, and will need to be installed manually for compiling
to wasm on other platforms. LLD is by default turned off in rustbuild, and
requires a `config.toml` option to be enabled to turn it on.
Finally the unstable `#![wasm_import_memory]` attribute was also removed as LLD
has a native option for controlling this.
[gc]: https://reviews.llvm.org/D42511
Disable NEON on musl ARMv7
`armv7-unknown-linux-musleabihf` target diverged a bit from `armv7-unknown-linux-gnueabihf` target. This PR re-syncs them.
Fix#47765.
Fix FreeBSD struct returning ABI.
FreeBSD has had a patch similar to this for a while. See https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=223047.
This reworks 6774e7a to be more specific about what `compute_abi_info` is checking for per target.
Add missing pieces for sparc-linux-gnu support
I noticed that while Rust has CABI support for 32-bit SPARC, there are still some pieces missing to be able to use Rust on a 32-Bit SPARC system like Gentoo which still defaults to a 32-bit port unlike Debian's sparc64 port.
This PR is an attempt to add the missing pieces. I will send the necessary changes for libc in a separate PR.
CC @jrtc27
[MSP430] Don't enable trap_unreachable option by default on msp.
Since MSP430 doesn't meaningfully support faulting on illegal
instructions, LLVM generates a call to abort() function instead
of a trap instruction. Such calls are 4 bytes long, and that is
too much overhead for such small target.
r? @alexcrichton
Since MSP430 doesn't meaningfully support faulting on illegal
instructions, LLVM generates a call to abort() function instead
of a trap instruction. Such calls are 4 bytes long, and that is
too much overhead for such small target.
This commit adds a new option to target specifictions to specify that symbols
should be "hidden" visibility by default in LLVM. While there are no existing
targets that take advantage of this the `wasm32-unknown-unknown` target will
soon start to use this visibility. The LLD linker currently interprets `hidden`
as "don't export this from the wasm module" which is what we want for 90% of our
functions. While the LLD linker does have a "export this symbol" argument which
is what we use for other linkers, it was also somewhat easier to do this change
instead which'll involve less arguments flying around. Additionally there's no
need for non-`hidden` visibility for most of our symbols!
This change should not immediately impact the wasm targets as-is, but rather
this is laying the foundations for soon integrating LLD as a linker for wasm
code.
This commit introduces a separately compiled backend for Emscripten, avoiding
compiling the `JSBackend` target in the main LLVM codegen backend. This builds
on the foundation provided by #47671 to create a new codegen backend dedicated
solely to Emscripten, removing the `JSBackend` of the main codegen backend in
the process.
A new field was added to each target for this commit which specifies the backend
to use for translation, the default being `llvm` which is the main backend that
we use. The Emscripten targets specify an `emscripten` backend instead of the
main `llvm` one.
There's a whole bunch of consequences of this change, but I'll try to enumerate
them here:
* A *second* LLVM submodule was added in this commit. The main LLVM submodule
will soon start to drift from the Emscripten submodule, but currently they're
both at the same revision.
* Logic was added to rustbuild to *not* build the Emscripten backend by default.
This is gated behind a `--enable-emscripten` flag to the configure script. By
default users should neither check out the emscripten submodule nor compile
it.
* The `init_repo.sh` script was updated to fetch the Emscripten submodule from
GitHub the same way we do the main LLVM submodule (a tarball fetch).
* The Emscripten backend, turned off by default, is still turned on for a number
of targets on CI. We'll only be shipping an Emscripten backend with Tier 1
platforms, though. All cross-compiled platforms will not be receiving an
Emscripten backend yet.
This commit means that when you download the `rustc` package in Rustup for Tier
1 platforms you'll be receiving two trans backends, one for Emscripten and one
that's the general LLVM backend. If you never compile for Emscripten you'll
never use the Emscripten backend, so we may update this one day to only download
the Emscripten backend when you add the Emscripten target. For now though it's
just an extra 10MB gzip'd.
Closes#46819
LLVM has since removed the `CodeModel::Default` enum value in favor of an
`Optional` implementationg throughout LLVM. Let's mirror the same change in Rust
and update the various bindings we call accordingly.
Removed in llvm-mirror/llvm@9aafb854c
Though some parts of rust use cc-rs to invoke a compiler/linker, Cargo
seems to make use of the TargetOptions::linker property. Make the out of
the box experience for CloudABI a bit better by using the same compiler
name as cc-rs.
Use the new fs_read_write functions in rustc internals
Uses `fs::read` and `fs::write` (added by #45837) where appropriate, to simplify code and dog-food these new APIs. This also improves performance, when combined with #47324.
Use the right TLS model for CloudABI.
CloudABI doesn't do dynamic linking. For this reason, there is no need
to handle any other TLS model than local-exec. CloudABI's C library
doesn't provide a __tls_get_addr() function to do Dynamic TLS.
By forcing local-exec to be used here, we ensure that we don't generate
function calls to __tls_get_addr().
CloudABI doesn't do dynamic linking. For this reason, there is no need
to handle any other TLS model than local-exec. CloudABI's C library
doesn't provide a __tls_get_addr() function to do Dynamic TLS.
By forcing local-exec to be used here, we ensure that we don't generate
function calls to __tls_get_addr().
This was originally brought in, because the definitions are based on
those of FreeBSD, Linux, etc. Even though CloudABI is based on POSIX, it
uses a subset that is so small that it's not reasonable to call it POSIX.
Now that I'm porting libstd, I'm running into some spots where I have to
explicitly disable code paths that were enabled by cfg(unix).
CloudABI is a sandboxed UNIX-like runtime environment. It is a
programming environment that uses a capability-based security model. In
practice this means that many POSIX interfaces are present, except for
ones that try to access resources out of thin air. For example, open()
is gone, but openat() is present.
Right now I'm at the point where I can compile very basic CloudABI
applications on all four supported architectures (ARM and x86, 32 and 64
bits). The next step will be to get libstd to work. Patches for that are
outside the scope of this change.
More info: https://nuxi.nl/cloudabi/https://github.com/NuxiNL/cloudlibc/
This commit adds a new target to the compiler: wasm32-unknown-unknown. This
target is a reimagining of what it looks like to generate WebAssembly code from
Rust. Instead of using Emscripten which can bring with it a weighty runtime this
instead is a target which uses only the LLVM backend for WebAssembly and a
"custom linker" for now which will hopefully one day be direct calls to lld.
Notable features of this target include:
* There is zero runtime footprint. The target assumes nothing exists other than
the wasm32 instruction set.
* There is zero toolchain footprint beyond adding the target. No custom linker
is needed, rustc contains everything.
* Very small wasm modules can be generated directly from Rust code using this
target.
* Most of the standard library is stubbed out to return an error, but anything
related to allocation works (aka `HashMap`, `Vec`, etc).
* Naturally, any `#[no_std]` crate should be 100% compatible with this new
target.
This target is currently somewhat janky due to how linking works. The "linking"
is currently unconditional whole program LTO (aka LLVM is being used as a
linker). Naturally that means compiling programs is pretty slow! Eventually
though this target should have a linker.
This target is also intended to be quite experimental. I'm hoping that this can
act as a catalyst for further experimentation in Rust with WebAssembly. Breaking
changes are very likely to land to this target, so it's not recommended to rely
on it in any critical capacity yet. We'll let you know when it's "production
ready".
---
Currently testing-wise this target is looking pretty good but isn't complete.
I've got almost the entire `run-pass` test suite working with this target (lots
of tests ignored, but many passing as well). The `core` test suite is still
getting LLVM bugs fixed to get that working and will take some time. Relatively
simple programs all seem to work though!
---
It's worth nothing that you may not immediately see the "smallest possible wasm
module" for the input you feed to rustc. For various reasons it's very difficult
to get rid of the final "bloat" in vanilla rustc (again, a real linker should
fix all this). For now what you'll have to do is:
cargo install --git https://github.com/alexcrichton/wasm-gc
wasm-gc foo.wasm bar.wasm
And then `bar.wasm` should be the smallest we can get it!
---
In any case for now I'd love feedback on this, particularly on the various
integration points if you've got better ideas of how to approach them!
This commit removes the `rand` crate from the standard library facade as
well as the `__rand` module in the standard library. Neither of these
were used in any meaningful way in the standard library itself. The only
need for randomness in libstd is to initialize the thread-local keys of
a `HashMap`, and that unconditionally used `OsRng` defined in the
standard library anyway.
The cruft of the `rand` crate and the extra `rand` support in the
standard library makes libstd slightly more difficult to port to new
platforms, namely WebAssembly which doesn't have any randomness at all
(without interfacing with JS). The purpose of this commit is to clarify
and streamline randomness in libstd, focusing on how it's only required
in one location, hashmap seeds.
Note that the `rand` crate out of tree has almost always been a drop-in
replacement for the `rand` crate in-tree, so any usage (accidental or
purposeful) of the crate in-tree should switch to the `rand` crate on
crates.io. This then also has the further benefit of avoiding
duplication (mostly) between the two crates!
