Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/api/src/trampoline/func.rs

@@ -0,0 +1,291 @@
+//! Support for a calling of an imported function.
+
+use crate::r#ref::HostRef;
+use anyhow::Result;
+use cranelift_codegen::ir::types;
+use cranelift_codegen::ir::{InstBuilder, StackSlotData, StackSlotKind, TrapCode};
+use cranelift_codegen::Context;
+use cranelift_codegen::{binemit, ir, isa};
+use cranelift_entity::{EntityRef, PrimaryMap};
+use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
+use cranelift_wasm::{DefinedFuncIndex, FuncIndex};
+use wasmtime_environ::{CompiledFunction, Export, Module};
+use wasmtime_jit::CodeMemory;
+use wasmtime_runtime::{InstanceHandle, VMContext, VMFunctionBody};
+
+use alloc::boxed::Box;
+use alloc::rc::Rc;
+use alloc::string::ToString;
+use alloc::vec::Vec;
+use core::cmp;
+
+use crate::{Callable, FuncType, Store, Trap, Val};
+
+use super::create_handle::create_handle;
+
+struct TrampolineState {
+    func: Rc<dyn Callable + 'static>,
+    trap: Option<HostRef<Trap>>,
+    #[allow(dead_code)]
+    code_memory: CodeMemory,
+}
+
+unsafe extern "C" fn stub_fn(vmctx: *mut VMContext, call_id: u32, values_vec: *mut i64) -> u32 {
+    let mut instance = InstanceHandle::from_vmctx(vmctx);
+
+    let (args, returns_len) = {
+        let module = instance.module_ref();
+        let signature = &module.signatures[module.functions[FuncIndex::new(call_id as usize)]];
+
+        let mut args = Vec::new();
+        for i in 1..signature.params.len() {
+            args.push(Val::read_value_from(
+                values_vec.offset(i as isize - 1),
+                signature.params[i].value_type,
+            ))
+        }
+        (args, signature.returns.len())
+    };
+
+    let mut returns = vec![Val::default(); returns_len];
+    let func = &instance
+        .host_state()
+        .downcast_mut::<TrampolineState>()
+        .expect("state")
+        .func;
+
+    match func.call(&args, &mut returns) {
+        Ok(()) => {
+            for i in 0..returns_len {
+                // TODO check signature.returns[i].value_type ?
+                returns[i].write_value_to(values_vec.offset(i as isize));
+            }
+            0
+        }
+        Err(trap) => {
+            // TODO read custom exception
+            InstanceHandle::from_vmctx(vmctx)
+                .host_state()
+                .downcast_mut::<TrampolineState>()
+                .expect("state")
+                .trap = Some(trap);
+            1
+        }
+    }
+}
+
+/// Create a trampoline for invoking a Callable.
+fn make_trampoline(
+    isa: &dyn isa::TargetIsa,
+    code_memory: &mut CodeMemory,
+    fn_builder_ctx: &mut FunctionBuilderContext,
+    call_id: u32,
+    signature: &ir::Signature,
+) -> *const VMFunctionBody {
+    // Mostly reverse copy of the similar method from wasmtime's
+    // wasmtime-jit/src/compiler.rs.
+    let pointer_type = isa.pointer_type();
+    let mut stub_sig = ir::Signature::new(isa.frontend_config().default_call_conv);
+
+    // Add the `vmctx` parameter.
+    stub_sig.params.push(ir::AbiParam::special(
+        pointer_type,
+        ir::ArgumentPurpose::VMContext,
+    ));
+
+    // Add the `call_id` parameter.
+    stub_sig.params.push(ir::AbiParam::new(types::I32));
+
+    // Add the `values_vec` parameter.
+    stub_sig.params.push(ir::AbiParam::new(pointer_type));
+
+    // Add error/trap return.
+    stub_sig.returns.push(ir::AbiParam::new(types::I32));
+
+    let values_vec_len = 8 * cmp::max(signature.params.len() - 1, signature.returns.len()) as u32;
+
+    let mut context = Context::new();
+    context.func =
+        ir::Function::with_name_signature(ir::ExternalName::user(0, 0), signature.clone());
+
+    let ss = context.func.create_stack_slot(StackSlotData::new(
+        StackSlotKind::ExplicitSlot,
+        values_vec_len,
+    ));
+    let value_size = 8;
+
+    {
+        let mut builder = FunctionBuilder::new(&mut context.func, fn_builder_ctx);
+        let block0 = builder.create_ebb();
+
+        builder.append_ebb_params_for_function_params(block0);
+        builder.switch_to_block(block0);
+        builder.seal_block(block0);
+
+        let values_vec_ptr_val = builder.ins().stack_addr(pointer_type, ss, 0);
+        let mflags = ir::MemFlags::trusted();
+        for i in 1..signature.params.len() {
+            if i == 0 {
+                continue;
+            }
+
+            let val = builder.func.dfg.ebb_params(block0)[i];
+            builder.ins().store(
+                mflags,
+                val,
+                values_vec_ptr_val,
+                ((i - 1) * value_size) as i32,
+            );
+        }
+
+        let vmctx_ptr_val = builder.func.dfg.ebb_params(block0)[0];
+        let call_id_val = builder.ins().iconst(types::I32, call_id as i64);
+
+        let callee_args = vec![vmctx_ptr_val, call_id_val, values_vec_ptr_val];
+
+        let new_sig = builder.import_signature(stub_sig.clone());
+
+        let callee_value = builder
+            .ins()
+            .iconst(pointer_type, stub_fn as *const VMFunctionBody as i64);
+        let call = builder
+            .ins()
+            .call_indirect(new_sig, callee_value, &callee_args);
+
+        let call_result = builder.func.dfg.inst_results(call)[0];
+        builder.ins().trapnz(call_result, TrapCode::User(0));
+
+        let mflags = ir::MemFlags::trusted();
+        let mut results = Vec::new();
+        for (i, r) in signature.returns.iter().enumerate() {
+            let load = builder.ins().load(
+                r.value_type,
+                mflags,
+                values_vec_ptr_val,
+                (i * value_size) as i32,
+            );
+            results.push(load);
+        }
+        builder.ins().return_(&results);
+        builder.finalize()
+    }
+
+    let mut code_buf: Vec<u8> = Vec::new();
+    let mut reloc_sink = RelocSink {};
+    let mut trap_sink = binemit::NullTrapSink {};
+    let mut stackmap_sink = binemit::NullStackmapSink {};
+    context
+        .compile_and_emit(
+            isa,
+            &mut code_buf,
+            &mut reloc_sink,
+            &mut trap_sink,
+            &mut stackmap_sink,
+        )
+        .expect("compile_and_emit");
+
+    let mut unwind_info = Vec::new();
+    context.emit_unwind_info(isa, &mut unwind_info);
+
+    code_memory
+        .allocate_for_function(&CompiledFunction {
+            body: code_buf,
+            jt_offsets: context.func.jt_offsets,
+            unwind_info,
+        })
+        .expect("allocate_for_function")
+        .as_ptr()
+}
+
+pub fn create_handle_with_function(
+    ft: &FuncType,
+    func: &Rc<dyn Callable + 'static>,
+    store: &HostRef<Store>,
+) -> Result<InstanceHandle> {
+    let sig = ft.get_cranelift_signature().clone();
+
+    let isa = {
+        let isa_builder =
+            cranelift_native::builder().expect("host machine is not a supported target");
+        let flag_builder = cranelift_codegen::settings::builder();
+        isa_builder.finish(cranelift_codegen::settings::Flags::new(flag_builder))
+    };
+
+    let mut fn_builder_ctx = FunctionBuilderContext::new();
+    let mut module = Module::new();
+    let mut finished_functions: PrimaryMap<DefinedFuncIndex, *const VMFunctionBody> =
+        PrimaryMap::new();
+    let mut code_memory = CodeMemory::new();
+
+    //let pointer_type = types::Type::triple_pointer_type(&HOST);
+    //let call_conv = isa::CallConv::triple_default(&HOST);
+
+    let sig_id = module.signatures.push(sig.clone());
+    let func_id = module.functions.push(sig_id);
+    module
+        .exports
+        .insert("trampoline".to_string(), Export::Function(func_id));
+    let trampoline = make_trampoline(
+        isa.as_ref(),
+        &mut code_memory,
+        &mut fn_builder_ctx,
+        func_id.index() as u32,
+        &sig,
+    );
+    code_memory.publish();
+
+    finished_functions.push(trampoline);
+
+    let trampoline_state = TrampolineState {
+        func: func.clone(),
+        trap: None,
+        code_memory,
+    };
+
+    create_handle(
+        module,
+        Some(store.borrow_mut()),
+        finished_functions,
+        Box::new(trampoline_state),
+    )
+}
+
+/// We don't expect trampoline compilation to produce any relocations, so
+/// this `RelocSink` just asserts that it doesn't recieve any.
+struct RelocSink {}
+
+impl binemit::RelocSink for RelocSink {
+    fn reloc_ebb(
+        &mut self,
+        _offset: binemit::CodeOffset,
+        _reloc: binemit::Reloc,
+        _ebb_offset: binemit::CodeOffset,
+    ) {
+        panic!("trampoline compilation should not produce ebb relocs");
+    }
+    fn reloc_external(
+        &mut self,
+        _offset: binemit::CodeOffset,
+        _reloc: binemit::Reloc,
+        _name: &ir::ExternalName,
+        _addend: binemit::Addend,
+    ) {
+        panic!("trampoline compilation should not produce external symbol relocs");
+    }
+    fn reloc_constant(
+        &mut self,
+        _code_offset: binemit::CodeOffset,
+        _reloc: binemit::Reloc,
+        _constant_offset: ir::ConstantOffset,
+    ) {
+        panic!("trampoline compilation should not produce constant relocs");
+    }
+    fn reloc_jt(
+        &mut self,
+        _offset: binemit::CodeOffset,
+        _reloc: binemit::Reloc,
+        _jt: ir::JumpTable,
+    ) {
+        panic!("trampoline compilation should not produce jump table relocs");
+    }
+}