Very detailed, thanks a lot
在 2023年10月10日星期二，'dmerc...@google.com' via v8-dev <v8-dev@googlegroups.com>
写道：
> Hi,
>
> Interestingly, even
>
> function Foo(s) {
> return s + "42";
> }
>
> Is enough to reach this case.
> Basically, as Leszek said, this happens when we have generic JSAdd and we
> can infer that one of the inputs is a String.
>
> In your example ("a + b"), we don't go into this path because we cannot
> infer the types of the inputs (the inputs are just Parameter[1] and
> Parameter[2], and we don't have feedback for parameters, just for
> operations). Still, because we have String feedback on the JSAdd, we decide
> a few lines later that we'll check that the inputs are string and we'll
> emit a StringConcat: https://chromium.googlesource.
> com/v8/v8.git/+/refs/tags/12.0.52/src/compiler/js-typed-lowering.cc#581.
>
> Cheers,
> Darius
>
>
> On Tuesday, October 10, 2023 at 1:50:32 PM UTC+2 les...@chromium.org
> wrote:
>
>> Hi,
>>
>> Most likely there would need to be some type inference inferring that one
>> of the inputs is a string, like an operation with known string result, e.g.
>>
>> function add2(a, b) {
>> let x = a + "string";
>> return x + b; // This would become JSAdd(x, JSToString(b))
>> }
>>
>> Hope that helps,
>> Leszek
>>
>> On Tue, Oct 10, 2023 at 12:52 PM zljj...@gmail.com <zljj...@gmail.com>
>> wrote:
>>
>>> Hi,
>>> https://chromium.googlesource.com/v8/v8.git/+/refs/tags/12.
>>> 0.52/src/compiler/js-typed-lowering.cc#565
>>> How to enter this optimaization path: JSAdd(x:string, y) => JSAdd(x,
>>> JSToString(y)) or
>>> JSAdd(x, y:string) => JSAdd(JSToString(x), y) ? The code below cannot
>>> enter this optimazation path, for input type is unknow.
>>>
>>> function add2(a, b) {
>>> return a + b;
>>> }
>>> // should create feedback vector at first, or type info can not collect.
>>> %PrepareFunctionForOptimization(add2);
>>> console.log(add2(1, "hello"));
>>> %OptimizeFunctionOnNextCall(add2);
>>> console.log(add2(2, "world"));
>>>
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