litmus5.js - mozsearch

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// Mutually recursive functions implement a multi-entry loop using indirect

// cross-module tail calls.  The functions do not have the same signatures, so

// if all arguments are stack arguments then these use different amounts of

// stack space.

//

// Cross-module mutual recursion must be set up by JS, which is a bit of hair.

// But this should not destroy the ability to tail-call.

//

// The variable ballast is intended to test that we handle various combinations

// of stack and register arguments properly.

//

// The mutable globals accessed after the call are there to attempt to ensure

// that the correct instance is restored after the chain of tail calls.

for ( let ballast=1; ballast < TailCallBallast; ballast++ ) {

    let vals = iota(ballast,1);

    let ps = vals.map(_ => 'i32').join(' ')

    let es = vals.map(i => `(local.get ${i})`).join(' ')

    let sum = vals.reduceRight((p,c) => `(i32.add (local.get ${c}) ${p})`, `(i32.const 0)`)

    let sumv = vals.reduce((p,c) => p+c);

    let odd_cookie = 24680246;

    let oddtext = `

(module

  (table (import "" "table") 2 2 funcref)

  (type $even_t (func (param i32 ${ps}) (result i32)))

  (global $glob (export "g") (mut i32) (i32.const ${odd_cookie}))

  (func $odd_entry (export "odd_entry") (param $n i32) (param ${ps}) (result i32)

    (call $odd (local.get $n) ${es} (i32.const 86))

    (global.get $glob)

    i32.add)

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

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

        (then (return (i32.or (i32.shl ${sum} (i32.const 1)) (i32.const 0))))

        (else (return_call_indirect (type $even_t) (i32.sub (local.get $n) (i32.const 1)) ${es} (i32.const 0))))))`

    let even_cookie = 12345678;

    let eventext = `

(module

  (table (import "" "table") 2 2 funcref)

  (type $odd_t (func (param i32 ${ps} i32) (result i32)))

  (global $glob (export "g") (mut i32) (i32.const ${even_cookie}))

  (func $even_entry (export "even_entry") (param $n i32) (param ${ps}) (result i32)

    (call $even (local.get $n) ${es})

    (global.get $glob)

    i32.add)

  (func $even (export "even") (param $n i32) (param ${ps}) (result i32)

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

        (then (return (i32.or (i32.shl ${sum} (i32.const 1)) (i32.const 1))))

        (else (return_call_indirect (type $odd_t) (i32.sub (local.get $n) (i32.const 1)) ${es} (i32.const 33) (i32.const 1))))))`

    let table = new WebAssembly.Table({initial:2, maximum:2, element:"funcref"})

    let oddins = wasmEvalText(oddtext, {"":{table}});

    let evenins = wasmEvalText(eventext, {"":{table}});

    table.set(0, evenins.exports.even);

    table.set(1, oddins.exports.odd);

    assertEq(evenins.exports.even_entry(TailCallIterations, ...vals), ((sumv*2) + 1) + even_cookie);

    assertEq(oddins.exports.odd_entry(TailCallIterations, ...vals, 33), ((sumv*2) + 0) + odd_cookie);