Minimal WASM JIT proof-of-concept

c-test-jit.c

#include <binaryen-c.h>
#include <emscripten.h>

#include <stdio.h>

typedef int (*iii_t)(int, int);

int adder_func(int a, int b) {
    return a + b;
}

int main() {
    BinaryenModuleRef m = BinaryenModuleCreate();
  
    // Create a function type for: i32 (i32, i32)
    BinaryenType params[2] = { BinaryenTypeInt32(), BinaryenTypeInt32() };
    BinaryenFunctionTypeRef iii = BinaryenAddFunctionType(m, "iii", BinaryenTypeInt32(), params, 2);
  
    // Get the 0 and 1 arguments, and forward them to `func`
    BinaryenExpressionRef adder_ptr, adder_res;
    BinaryenExpressionRef operands[2];
    operands[0] = BinaryenGetLocal(m, 0, BinaryenTypeInt32());
    operands[1] = BinaryenGetLocal(m, 1, BinaryenTypeInt32());
    adder_ptr = BinaryenConst(m, BinaryenLiteralInt32((uintptr_t)adder_func));
    adder_res = BinaryenCallIndirect(m, adder_ptr, operands, 2, "iii");
  
    // Create the wrapper function (no local variables, no basic blocks)
    BinaryenAddFunction(m, "adder_wrapper", iii, NULL, 0, adder_res);
    BinaryenAddFunctionExport(m, "adder_wrapper", "adder_wrapper");

    BinaryenAddMemoryImport(m, NULL, "env", "memory", 0);
    BinaryenAddTableImport(m, NULL, "env", "table");

    // Print module and generate bytecode
    BinaryenModuleAllocateAndWriteResult result;
    assert(BinaryenModuleValidate(m));
    BinaryenModuleOptimize(m);
    BinaryenModulePrint(m);
    result = BinaryenModuleAllocateAndWrite(m, NULL);

    // Link module
    uint32_t adder_wrapper_index = EM_ASM_INT({
        var jit_binary = new Uint8Array(wasmMemory.buffer, $0, $1);
        var jit_module = new WebAssembly.Module(jit_binary);
        var jit_instance = new WebAssembly.Instance(jit_module, {
            env: {
                memory: wasmMemory,
                table: wasmTable,
            }
        });
        var adder_wrapper = jit_instance.exports["adder_wrapper"];
        var adder_wrapper_index = addWasmFunction(adder_wrapper);
        return adder_wrapper_index;
    }, result.binary, result.binaryBytes);

    // Clean up the module, which owns all objects above, and free the bytecode
    BinaryenModuleDispose(m);
    free(result.binary);

    // Execute code!
    int a = 3;
    int b = 4;
    iii_t adder_wrapper = (iii_t)adder_wrapper_index;
    printf("adder_wrapper(%d, %d) = %d\n", a, b, adder_wrapper(a, b));    

    return 0;
}