9ac7d01288
This commit is intended to do almost everything necessary for processing the alias section of module linking. Most of this is internal refactoring, the highlights being: * Type contents are now stored separately from a `wasmtime_env::Module`. Given that modules can freely alias types and have them used all over the place, it seemed best to have one canonical location to type storage which everywhere else points to (with indices). A new `TypeTables` structure is produced during compilation which is shared amongst all member modules in a wasm blob. * Instantiation is heavily refactored to account for module linking. The main gotcha here is that imports are now listed as "initializers". We have a sort of pseudo-bytecode-interpreter which interprets the initialization of a module. This is more complicated than just matching imports at this point because in the module linking proposal the module, alias, import, and instance sections may all be interleaved. This means that imports aren't guaranteed to show up at the beginning of the address space for modules/instances. Otherwise most of the changes here largely fell out from these two design points. Aliases are recorded as initializers in this scheme. Copying around type information and/or just knowing type information during compilation is also pretty easy since everything is just a pointer into a `TypeTables` and we don't have to actually copy any types themselves. Lots of various refactorings were necessary to accomodate these changes. Tests are hoped to cover a breadth of functionality here, but not necessarily a depth. There's still one more piece of the module linking proposal missing which is exporting instances/modules, which will come in a future PR. It's also worth nothing that there's one large TODO which isn't implemented in this change that I plan on opening an issue for. With module linking when a set of modules comes back from compilation each modules has all the trampolines for the entire set of modules. This is quite a lot of duplicate trampolines across module-linking modules. We'll want to refactor this at some point to instead have only one set of trampolines per set of module linking modules and have them shared from there. I figured it was best to separate out this change, however, since it's purely related to resource usage, and doesn't impact non-module-linking modules at all. cc #2094
70 lines
2.6 KiB
Rust
70 lines
2.6 KiB
Rust
//! Object file generation.
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use super::trampoline::build_trampoline;
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use cranelift_frontend::FunctionBuilderContext;
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use object::write::Object;
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use serde::{Deserialize, Serialize};
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use wasmtime_debug::DwarfSection;
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use wasmtime_environ::entity::PrimaryMap;
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use wasmtime_environ::isa::{unwind::UnwindInfo, TargetIsa};
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use wasmtime_environ::wasm::{FuncIndex, SignatureIndex};
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use wasmtime_environ::{CompiledFunctions, ModuleTranslation, TypeTables};
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use wasmtime_obj::{ObjectBuilder, ObjectBuilderTarget};
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pub use wasmtime_obj::utils;
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/// Unwind information for object files functions (including trampolines).
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#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
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pub enum ObjectUnwindInfo {
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Func(FuncIndex, UnwindInfo),
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Trampoline(SignatureIndex, UnwindInfo),
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}
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// Builds ELF image from the module `Compilation`.
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pub(crate) fn build_object(
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isa: &dyn TargetIsa,
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translation: &ModuleTranslation,
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types: &TypeTables,
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funcs: &CompiledFunctions,
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dwarf_sections: Vec<DwarfSection>,
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) -> Result<(Object, Vec<ObjectUnwindInfo>), anyhow::Error> {
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const CODE_SECTION_ALIGNMENT: u64 = 0x1000;
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let mut unwind_info = Vec::new();
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// Preserve function unwind info.
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unwind_info.extend(funcs.iter().filter_map(|(index, func)| {
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func.unwind_info
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.as_ref()
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.map(|info| ObjectUnwindInfo::Func(translation.module.func_index(index), info.clone()))
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}));
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let mut trampolines = PrimaryMap::with_capacity(types.native_signatures.len());
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let mut cx = FunctionBuilderContext::new();
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// Build trampolines for every signature.
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//
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// TODO: for the module linking proposal this builds too many native
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// signatures. This builds trampolines for all signatures for all modules
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// for each module. That's a lot of trampolines! We should instead figure
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// out a way to share trampolines amongst all modules when compiling
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// module-linking modules.
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for (i, native_sig) in types.native_signatures.iter() {
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let func = build_trampoline(isa, &mut cx, native_sig, std::mem::size_of::<u128>())?;
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// Preserve trampoline function unwind info.
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if let Some(info) = &func.unwind_info {
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unwind_info.push(ObjectUnwindInfo::Trampoline(i, info.clone()))
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}
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trampolines.push(func);
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}
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let target = ObjectBuilderTarget::new(isa.triple().architecture)?;
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let mut builder = ObjectBuilder::new(target, &translation.module, funcs);
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builder
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.set_code_alignment(CODE_SECTION_ALIGNMENT)
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.set_trampolines(trampolines)
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.set_dwarf_sections(dwarf_sections);
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let obj = builder.build()?;
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Ok((obj, unwind_info))
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}
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