1780010 - Improve generated code for EqualChars and some further clean-ups

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement, P1)

Description

[André Bargull [:anba]]

EqualChars generates sub-optimal code when comparing Latin1Char* against char*: https://godbolt.org/z/5oG6hhd9G.

Also perform some additional clean-ups around EqualChars callers. For example:

• Use std::string_view where applicable.
• Replace sizeof where applicable.

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 1: Special-case Latin1Char with char comparison in EqualChars. r=jandem!

Compilers don't emit memcmp when the both inputs aren't exactly the same type.

Comment 2

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 2: Replace ArrayEqual with EqualChars. r=jandem!

This makes the code a bit more uniform.

The previous part should make bug 1589591 obsolete, so it seems useful to make
the code more uniform.

Depends on D152040

Comment 3

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 3: Use EqualChars to compare Infinity/NaN for TypedArray indices. r=jandem!

Part 1 ensures we generate fast code when comparing against constant char*
strings, so we no longer need the more complicated code.

Depends on D152042

Comment 4

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 4: Store "Infinity" as string_view in js_strtod. r=jandem!

std::string_view stores a pointer and its length, so we no longer have to
use two different variables. std::string_view methods are also const_expr,
so the compiler will inline them at compile-time.

Depends on D152043

Comment 5

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 5: Use string_view in more places. r=jandem!

builtin/Object.cpp:

• Using string_view avoids the call to strlen when Consume isn't inlined.

jsapi-tests/testCompileNonSyntactic.cpp:
shell/jsoptparse.cpp:
xpconnect/src/XPCWrappedNativeJSOps.cpp:

• Using string_view avoids the sizeof - 1 pattern.

Depends on D152044

Comment 6

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 6: Replace sizeof with std::string_view for function strings. r=jandem!

std::char_traits<char>::length is longer than sizeof - 1, but avoids knowing
how the sizeof - 1 pattern works.

Depends on D152045

Comment 7

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 7: Replace sizeof with std::end(). r=jandem!

Depends on D152047

Comment 8

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 8: Replace sizeof with enhanced for-loop. r=jandem!

Depends on D152048

Comment 9

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 9: Replace sizeof with std::size(). r=jandem!

Depends on D152049

Comment 10

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 10: Use initialiser syntax instead of memset to zero allocate. r=jandem!

Noticed while checking for more sizeof uses across the code base.

Depends on D152051

Comment 11

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 11: Use calloc instead of malloc + memset to zero allocate memory. r=jandem!

Noticed because the last part changed memset callers.

Depends on D152052

Comment 13

[André Bargull [:anba]]

Attachment: Bug 1780010 - Part 12: Don't pass an explicit string length when the compiler can compute it. r=jandem!

Comment 14

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/de03ad94fa30
Part 1: Special-case Latin1Char with char comparison in EqualChars. r=jandem
https://hg.mozilla.org/integration/autoland/rev/03deb487524f
Part 2: Replace ArrayEqual with EqualChars. r=jandem
https://hg.mozilla.org/integration/autoland/rev/caec1c0fd0cf
Part 3: Use EqualChars to compare Infinity/NaN for TypedArray indices. r=jandem
https://hg.mozilla.org/integration/autoland/rev/4617fbe2c524
Part 4: Store "Infinity" as string_view in js_strtod. r=jandem
https://hg.mozilla.org/integration/autoland/rev/253fba58019e
Part 5: Use string_view in more places. r=jandem
https://hg.mozilla.org/integration/autoland/rev/effe68106173
Part 6: Replace sizeof with std::string_view for function strings. r=jandem
https://hg.mozilla.org/integration/autoland/rev/d5a41f935dc1
Part 7: Replace sizeof with std::end(). r=jandem
https://hg.mozilla.org/integration/autoland/rev/eb4437561337
Part 8: Replace sizeof with enhanced for-loop. r=jandem
https://hg.mozilla.org/integration/autoland/rev/ee6bcfc78607
Part 9: Replace sizeof with std::size(). r=jandem
https://hg.mozilla.org/integration/autoland/rev/d66a2324bd75
Part 10: Use initialiser syntax instead of memset to zero allocate. r=jandem
https://hg.mozilla.org/integration/autoland/rev/6c88654690bf
Part 11: Use calloc instead of malloc + memset to zero allocate memory. r=jandem
https://hg.mozilla.org/integration/autoland/rev/18d92d17a23b
Part 12: Don't pass an explicit string length when the compiler can compute it. r=jandem

Comment 15

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/de03ad94fa30
https://hg.mozilla.org/mozilla-central/rev/03deb487524f
https://hg.mozilla.org/mozilla-central/rev/caec1c0fd0cf
https://hg.mozilla.org/mozilla-central/rev/4617fbe2c524
https://hg.mozilla.org/mozilla-central/rev/253fba58019e
https://hg.mozilla.org/mozilla-central/rev/effe68106173
https://hg.mozilla.org/mozilla-central/rev/d5a41f935dc1
https://hg.mozilla.org/mozilla-central/rev/eb4437561337
https://hg.mozilla.org/mozilla-central/rev/ee6bcfc78607
https://hg.mozilla.org/mozilla-central/rev/d66a2324bd75
https://hg.mozilla.org/mozilla-central/rev/6c88654690bf
https://hg.mozilla.org/mozilla-central/rev/18d92d17a23b