1591359 - [BinAST] Optimize HuffmanDictionary.{fields_,listLengths_} initialization code

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P3)

Description

[Tooru Fujisawa [:arai]]

Currently (even after bug 1590683 patch), HuffmanDictionary::HuffmanDictionary ctor code is like the following:

    pushq  %rbp
    movq   %rsp, %rbp
    movb   $0x0, 0x58(%rdi)
    movb   $0x0, 0xb8(%rdi)
    movb   $0x0, 0x118(%rdi)
    movb   $0x0, 0x178(%rdi)
    movb   $0x0, 0x1d8(%rdi)
    movb   $0x0, 0x238(%rdi)
    movb   $0x0, 0x298(%rdi)
    movb   $0x0, 0x2f8(%rdi)
    movb   $0x0, 0x358(%rdi)
    movb   $0x0, 0x3b8(%rdi)
    movb   $0x0, 0x418(%rdi)
... (skip 284 lines of movb)
    movb   $0x0, 0x6ef8(%rdi)
    movb   $0x0, 0x6f58(%rdi)
    popq   %rbp
    retq

This is initialization of arrays of Variants, HuffmanDictionary.{fields_,listLengths_}, and each operation sets the tag to HuffmanTableUnreachable.

Given we don't need HuffmanTableValue to be Variant after bug 1590683, but just want unused GenericHuffmanTable uninitialized,
if we store the tag (flag) and the uninitialized array of GenericHuffmanTable separately,
the operation can be done with smaller code and also maybe quickly.
(we need some special code to manage array of uninitialized/initialized instances tho)

also, if we use something else than Array, we can remove BINAST_PARAM_NUMBER_OF_* macros.

Comment 1

[Tooru Fujisawa [:arai]]

when parsing 200 small files, HuffmanDictionary ctor takes 1.1% of the total time.

Comment 2

[Tooru Fujisawa [:arai]]

Attachment: Bug 1591359 - Part 1: Separate HuffmanTableValue& array into TableStatus array and uninitialized GenericHuffmanTable array. r?Yoric

Comment 3

[Tooru Fujisawa [:arai]]

Attachment: Bug 1591359 - Part 2: Rename HuffmanTableUnreachable to TableImplementationUninitialized. r?Yoric

Depends on D50597

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/50a9344008a3
Part 1: Separate HuffmanTableValue& array into TableStatus array and uninitialized GenericHuffmanTable array. r=Yoric
https://hg.mozilla.org/integration/autoland/rev/d9cf158e085b
Part 2: Rename HuffmanTableUnreachable to TableImplementationUninitialized. r=Yoric

Comment 5

[Stefan Hindli [:stefan_hindli]]

https://hg.mozilla.org/mozilla-central/rev/50a9344008a3
https://hg.mozilla.org/mozilla-central/rev/d9cf158e085b