Bug 22897 – Clear bytecode vector after JITing

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Sam Weinig]

Clearing the bytecode vector after JITing will save about 4.8MB on Membuster head.

[Sam Weinig]

Created attachment 26087 [details]
patch

[Darin Adler]

Comment on attachment 26087 [details]
patch

> +        (JSC::CodeBlock::handlerForBytecodeOffset): Don't assert that the offset
> +        is less than the size of the bytecode vector since it may have been cleared
> +        and therefore 0.

I think it would be better to keep around the size of the bytecode vector in a separate variable in debug versions so we could keep these assertions.

r=me

[Geoffrey Garen]

Comment on attachment 26087 [details]
patch

>      m_codeBlock->setJITCode(codeRef);
> +#if !ENABLE(OPCODE_SAMPLING)
> +    m_codeBlock->instructions().clear();
> +#endif

I think it would be better to do this:

#if ENABLE(OPCODE_SAMPLING)
    // Don't clear instructions -- we need them for sampling.
#elsif !defined(NDEBUG)
    if (!s_dumpsGeneratedCode)
        m_codeBlock->instructions().clear();
#else
    m_codeBlock->instructions().clear();
#endif

[Geoffrey Garen]

> I think it would be better to do this:

That way, you can still dump code in debug builds.

[Sam Weinig]

Fixed in r39366.