wasmer_compiler_cranelift/trampoline/
function_call.rs

1// This file contains code from external sources.
2// Attributions: https://github.com/wasmerio/wasmer/blob/main/docs/ATTRIBUTIONS.md
3
4//! A trampoline generator for calling Wasm functions easily.
5//!
6//! That way, you can start calling Wasm functions doing things like:
7//! ```ignore
8//! let my_func = instance.exports.get("func");
9//! my_func.call([1, 2])
10//! ```
11use crate::{
12    CraneliftCallbacks,
13    translator::{compiled_function_unwind_info, signature_to_cranelift_ir},
14};
15use cranelift_codegen::{
16    Context,
17    ir::{self, InstBuilder},
18    isa::TargetIsa,
19};
20use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
21use std::mem;
22use target_lexicon::Architecture;
23use wasmer_compiler::{misc::CompiledKind, types::function::FunctionBody};
24use wasmer_types::{CompileError, FunctionType};
25
26/// Create a trampoline for invoking a WebAssembly function.
27pub fn make_trampoline_function_call(
28    callbacks: &Option<CraneliftCallbacks>,
29    isa: &dyn TargetIsa,
30    arch: Architecture,
31    fn_builder_ctx: &mut FunctionBuilderContext,
32    func_type: &FunctionType,
33) -> Result<FunctionBody, CompileError> {
34    let pointer_type = isa.pointer_type();
35    let frontend_config = isa.frontend_config();
36    let signature = signature_to_cranelift_ir(func_type, frontend_config);
37    let mut wrapper_sig = ir::Signature::new(frontend_config.default_call_conv);
38
39    // Add the callee `vmctx` parameter.
40    wrapper_sig.params.push(ir::AbiParam::special(
41        pointer_type,
42        ir::ArgumentPurpose::VMContext,
43    ));
44
45    // Add the `callee_address` parameter.
46    wrapper_sig.params.push(ir::AbiParam::new(pointer_type));
47
48    // Add the `values_vec` parameter.
49    wrapper_sig.params.push(ir::AbiParam::new(pointer_type));
50
51    let mut context = Context::new();
52    context.func = ir::Function::with_name_signature(ir::UserFuncName::user(0, 0), wrapper_sig);
53
54    let value_size = mem::size_of::<u128>();
55    {
56        let mut builder = FunctionBuilder::new(&mut context.func, fn_builder_ctx);
57        let block0 = builder.create_block();
58
59        builder.append_block_params_for_function_params(block0);
60        builder.switch_to_block(block0);
61        builder.seal_block(block0);
62
63        let (vmctx_ptr_val, callee_value, values_vec_ptr_val) = {
64            let params = builder.func.dfg.block_params(block0);
65            (params[0], params[1], params[2])
66        };
67
68        // Load the argument values out of `values_vec`.
69        let mflags = ir::MemFlags::trusted();
70        let callee_args = signature
71            .params
72            .iter()
73            .enumerate()
74            .map(|(i, r)| {
75                match i {
76                    0 => vmctx_ptr_val,
77                    _ =>
78                    // i - 1 because vmctx is not passed through `values_vec`.
79                    {
80                        builder.ins().load(
81                            r.value_type,
82                            mflags,
83                            values_vec_ptr_val,
84                            ((i - 1) * value_size) as i32,
85                        )
86                    }
87                }
88            })
89            .collect::<Vec<_>>();
90
91        let new_sig = builder.import_signature(signature);
92
93        let call = builder
94            .ins()
95            .call_indirect(new_sig, callee_value, &callee_args);
96
97        let results = builder.func.dfg.inst_results(call).to_vec();
98
99        // Store the return values into `values_vec`.
100        let mflags = ir::MemFlags::trusted();
101        for (i, r) in results.iter().enumerate() {
102            builder
103                .ins()
104                .store(mflags, *r, values_vec_ptr_val, (i * value_size) as i32);
105        }
106
107        builder.ins().return_(&[]);
108        builder.finalize()
109    }
110
111    if let Some(callbacks) = callbacks.as_ref() {
112        callbacks.preopt_ir(
113            &CompiledKind::FunctionCallTrampoline(func_type.clone()),
114            context.func.display().to_string().as_bytes(),
115        );
116    }
117
118    let mut code_buf = Vec::new();
119    let mut ctrl_plane = Default::default();
120    let compiled = context
121        .compile(isa, &mut ctrl_plane)
122        .map_err(|error| CompileError::Codegen(error.inner.to_string()))?;
123    code_buf.extend_from_slice(compiled.code_buffer());
124
125    if let Some(callbacks) = callbacks.as_ref() {
126        callbacks.obj_memory_buffer(
127            &CompiledKind::FunctionCallTrampoline(func_type.clone()),
128            &code_buf,
129        );
130        callbacks.asm_memory_buffer(
131            &CompiledKind::FunctionCallTrampoline(func_type.clone()),
132            arch,
133            &code_buf,
134        )?;
135    }
136
137    let unwind_info = compiled_function_unwind_info(isa, &context)?.maybe_into_to_windows_unwind();
138
139    Ok(FunctionBody {
140        body: code_buf,
141        unwind_info,
142    })
143}
wasmer_compiler_cranelift/trampoline/function_call.rs

wasmer_compiler_cranelift/trampoline/
function_call.rs
