litmus3.js - mozsearch

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// Mutually recursive functions implement a multi-entry loop using tail calls,

// with exception handling.

//

// The functions do not have the same signatures, so if all arguments are stack

// arguments then these use different amounts of stack space.

//

// The "even" function will throw when the input is zero, so when an exception

// bubbles out of return_call it must not be caught by the exception handler in

// "odd", but must instead be delegated to the caller, which is JS code.

var ins = wasmEvalText(`

(module

  (tag $t)

  (func $odd (export "odd") (param $n i32) (param $dummy i32) (result i32)

    try (result i32)

    (if (result i32) (i32.eqz (local.get $n))

        (then (return (i32.const 0)))

        (else (return_call $even (i32.sub (local.get $n) (i32.const 1)))))

    catch_all

      unreachable

    end)

  (func $even (export "even") (param $n i32) (result i32)

    (if (result i32) (i32.eqz (local.get $n))

        (then (throw $t))

        (else (return_call $odd (i32.sub (local.get $n) (i32.const 1)) (i32.const 33)))))

`);

assertErrorMessage(() => ins.exports.even(TailCallIterations), WebAssembly.Exception, /.*/);

assertEq(ins.exports.odd(TailCallIterations, 33), 0);

assertEq(ins.exports.even(TailCallIterations+1), 0);

assertErrorMessage(() => ins.exports.odd(TailCallIterations+1, 33), WebAssembly.Exception, /.*/);