39e57e3e9a
* Migrate back to `std::` stylistically This commit moves away from idioms such as `alloc::` and `core::` as imports of standard data structures and types. Instead it migrates all crates to uniformly use `std::` for importing standard data structures and types. This also removes the `std` and `core` features from all crates to and removes any conditional checking for `feature = "std"` All of this support was previously added in #407 in an effort to make wasmtime/cranelift "`no_std` compatible". Unfortunately though this change comes at a cost: * The usage of `alloc` and `core` isn't idiomatic. Especially trying to dual between types like `HashMap` from `std` as well as from `hashbrown` causes imports to be surprising in some cases. * Unfortunately there was no CI check that crates were `no_std`, so none of them actually were. Many crates still imported from `std` or depended on crates that used `std`. It's important to note, however, that **this does not mean that wasmtime will not run in embedded environments**. The style of the code today and idioms aren't ready in Rust to support this degree of multiplexing and makes it somewhat difficult to keep up with the style of `wasmtime`. Instead it's intended that embedded runtime support will be added as necessary. Currently only `std` is necessary to build `wasmtime`, and platforms that natively need to execute `wasmtime` will need to use a Rust target that supports `std`. Note though that not all of `std` needs to be supported, but instead much of it could be configured off to return errors, and `wasmtime` would be configured to gracefully handle errors. The goal of this PR is to move `wasmtime` back to idiomatic usage of features/`std`/imports/etc and help development in the short-term. Long-term when platform concerns arise (if any) they can be addressed by moving back to `no_std` crates (but fixing the issues mentioned above) or ensuring that the target in Rust has `std` available. * Start filling out platform support doc
93 lines
3.4 KiB
Rust
93 lines
3.4 KiB
Rust
#![allow(clippy::cast_ptr_alignment)]
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use cranelift_codegen::isa::TargetFrontendConfig;
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use cranelift_entity::EntityRef;
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use cranelift_wasm::GlobalInit;
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use more_asserts::assert_le;
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use std::collections::hash_map::Entry;
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use std::collections::HashMap;
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use std::ptr;
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use wasmtime_environ::{Module, TargetSharedSignatureIndex, VMOffsets};
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pub struct TableRelocation {
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pub index: usize,
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pub offset: usize,
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}
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pub fn layout_vmcontext(
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module: &Module,
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target_config: &TargetFrontendConfig,
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) -> (Box<[u8]>, Box<[TableRelocation]>) {
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let ofs = VMOffsets::new(target_config.pointer_bytes(), &module);
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let out_len = ofs.size_of_vmctx() as usize;
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let mut out = vec![0; out_len];
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// Assign unique indicies to unique signatures.
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let mut signature_registry = HashMap::new();
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let mut signature_registry_len = signature_registry.len();
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for (index, sig) in module.signatures.iter() {
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let offset = ofs.vmctx_vmshared_signature_id(index) as usize;
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let target_index = match signature_registry.entry(sig) {
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Entry::Occupied(o) => *o.get(),
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Entry::Vacant(v) => {
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assert_le!(signature_registry_len, std::u32::MAX as usize);
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let id = TargetSharedSignatureIndex::new(signature_registry_len as u32);
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signature_registry_len += 1;
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*v.insert(id)
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}
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};
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unsafe {
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let to = out.as_mut_ptr().add(offset) as *mut TargetSharedSignatureIndex;
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ptr::write(to, target_index);
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}
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}
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let num_tables_imports = module.imported_tables.len();
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let mut table_relocs = Vec::with_capacity(module.table_plans.len() - num_tables_imports);
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for (index, table) in module.table_plans.iter().skip(num_tables_imports) {
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let def_index = module.defined_table_index(index).unwrap();
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let offset = ofs.vmctx_vmtable_definition(def_index) as usize;
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let current_elements = table.table.minimum;
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unsafe {
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assert_eq!(
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::std::mem::size_of::<u32>() as u8,
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ofs.size_of_vmtable_definition_current_elements(),
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"vmtable_definition_current_elements expected to be u32"
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);
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let to = out
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.as_mut_ptr()
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.add(offset)
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.add(ofs.vmtable_definition_current_elements() as usize);
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ptr::write(to as *mut u32, current_elements);
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}
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table_relocs.push(TableRelocation {
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index: def_index.index(),
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offset,
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});
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}
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let num_globals_imports = module.imported_globals.len();
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for (index, global) in module.globals.iter().skip(num_globals_imports) {
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let def_index = module.defined_global_index(index).unwrap();
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let offset = ofs.vmctx_vmglobal_definition(def_index) as usize;
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let to = unsafe { out.as_mut_ptr().add(offset) };
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match global.initializer {
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GlobalInit::I32Const(x) => unsafe {
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ptr::write(to as *mut i32, x);
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},
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GlobalInit::I64Const(x) => unsafe {
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ptr::write(to as *mut i64, x);
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},
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GlobalInit::F32Const(x) => unsafe {
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ptr::write(to as *mut u32, x);
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},
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GlobalInit::F64Const(x) => unsafe {
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ptr::write(to as *mut u64, x);
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},
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_ => panic!("unsupported global type"),
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}
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}
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(out.into_boxed_slice(), table_relocs.into_boxed_slice())
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}
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