Skip to content

Update calling conventions for wasm functions slightly #6676

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Jul 6, 2023
Merged

Update calling conventions for wasm functions slightly #6676

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
25f6444
Update calling conventions for wasm functions slightly
alexcrichton Jun 30, 2023
b5fe111
Fix compile
alexcrichton Jun 30, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
33 changes: 21 additions & 12 deletions crates/cranelift/src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ use cranelift_codegen::ir;
use cranelift_codegen::isa::{CallConv, TargetIsa};
use cranelift_entity::PrimaryMap;
use cranelift_wasm::{DefinedFuncIndex, WasmFuncType, WasmType};
use target_lexicon::CallingConvention;
use target_lexicon::Architecture;
use wasmtime_cranelift_shared::CompiledFunctionMetadata;

pub use builder::builder;
Expand Down Expand Up @@ -126,18 +126,27 @@ fn array_call_signature(isa: &dyn TargetIsa) -> ir::Signature {

/// Get the internal Wasm calling convention signature for the given type.
fn wasm_call_signature(isa: &dyn TargetIsa, wasm_func_ty: &WasmFuncType) -> ir::Signature {
let call_conv = if isa.triple().default_calling_convention().ok()
== Some(CallingConvention::AppleAarch64)
{
// FIXME: We need an Apple-specific calling convention, so that
// Cranelift's ABI implementation generates unwinding directives
// about pointer authentication usage, so we can't just use
// `CallConv::Fast`.
CallConv::AppleAarch64
} else {
CallConv::Fast
};
// NB: this calling convention in the near future is expected to be
// unconditionally switched to the "tail" calling convention once all
// platforms have support for tail calls.
//
// Also note that the calling convention for wasm functions is purely an
// internal implementation detail of cranelift and Wasmtime. Native Rust
// code does not interact with raw wasm functions and instead always
// operates through trampolines either using the `array_call_signature` or
// `native_call_signature` where the default platform ABI is used.
let call_conv = match isa.triple().architecture {
// On s390x the "wasmtime" calling convention is used to give vectors
// little-endian lane order at the ABI layer which should reduce the
// need for conversion when operating on vector function arguments. By
// default vectors on s390x are otherwise in big-endian lane order which
// would require conversions.
Architecture::S390x => CallConv::WasmtimeSystemV,

// All other platforms pick "fast" as the calling convention since it's
// presumably, well, the fastest.
_ => CallConv::Fast,
};
let mut sig = blank_sig(isa, call_conv);
let cvt = |ty: &WasmType| ir::AbiParam::new(value_type(isa, *ty));
sig.params.extend(wasm_func_ty.params().iter().map(&cvt));
Expand Down