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Remove extern "wasm" ABI

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Remove the unstable `extern "wasm"` ABI (`wasm_abi` feature tracked
in #83788).

As discussed in https://github.com/rust-lang/rust/pull/127513#issuecomment-2220410679
and following, this ABI is a failed experiment that did not end
up being used for anything. Keeping support for this ABI in LLVM 19
would require us to switch wasm targets to the `experimental-mv`
ABI, which we do not want to do.

It should be noted that `Abi::Wasm` was internally used for two
things: The `-Z wasm-c-abi=legacy` ABI that is still used by
default on some wasm targets, and the `extern "wasm"` ABI. Despite
both being `Abi::Wasm` internally, they were not the same. An
explicit `extern "wasm"` additionally enabled the `+multivalue`
feature.

I've opted to remove `Abi::Wasm` in this patch entirely, instead
of keeping it as an ABI with only internal usage. Both
`-Z wasm-c-abi` variants are now treated as part of the normal
C ABI, just with different different treatment in
adjust_for_foreign_abi.
This commit is contained in:
Nikita Popov 2024-07-10 17:20:21 +02:00
parent 0fdfb61795
commit 8a50bcbdce
25 changed files with 87 additions and 382 deletions
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14
compiler/rustc_codegen_llvm/src/attributes.rs
View file

@ -6,7 +6,6 @@ use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, PatchableFuncti
use rustc_middle::ty::{self, TyCtxt};
use rustc_session::config::{FunctionReturn, OptLevel};
use rustc_span::symbol::sym;
use rustc_target::spec::abi::Abi;
use rustc_target::spec::{FramePointer, SanitizerSet, StackProbeType, StackProtector};
use smallvec::SmallVec;
@ -482,7 +481,7 @@ pub fn from_fn_attrs<'ll, 'tcx>(
return;
}
let mut function_features = function_features
let function_features = function_features
.iter()
.flat_map(|feat| {
llvm_util::to_llvm_features(cx.tcx.sess, feat).into_iter().map(|f| format!("+{f}"))
@ -504,17 +503,6 @@ pub fn from_fn_attrs<'ll, 'tcx>(
let name = name.as_str();
to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-name", name));
}
// The `"wasm"` abi on wasm targets automatically enables the
// `+multivalue` feature because the purpose of the wasm abi is to match
// the WebAssembly specification, which has this feature. This won't be
// needed when LLVM enables this `multivalue` feature by default.
if !cx.tcx.is_closure_like(instance.def_id()) {
let abi = cx.tcx.fn_sig(instance.def_id()).skip_binder().abi();
if abi == Abi::Wasm {
function_features.push("+multivalue".to_string());
}
}
}
let global_features = cx.tcx.global_backend_features(()).iter().map(|s| s.as_str());