[webkit-changes] [WebKit/WebKit] 0f30a2: [JSC] Relanding 280425 at main with tweaks

[Yusuke Suzuki]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 0f30a2dccb2841b4fe0fb2a3bb10c399a366bf71
      https://github.com/WebKit/WebKit/commit/0f30a2dccb2841b4fe0fb2a3bb10c399a366bf71
  Author: Yusuke Suzuki <ysuzuki at apple.com>
  Date:   2024-08-23 (Fri, 23 Aug 2024)

  Changed paths:
    A JSTests/microbenchmarks/regexp-match-alphanumeric.js
    A JSTests/microbenchmarks/regexp-match-multiple-single-chars.js
    A JSTests/microbenchmarks/regexp-match-separators.js
    M Source/JavaScriptCore/assembler/MacroAssembler.h
    M Source/JavaScriptCore/assembler/MacroAssemblerARM64.h
    M Source/JavaScriptCore/assembler/MacroAssemblerARMv7.h
    M Source/JavaScriptCore/assembler/MacroAssemblerRISCV64.h
    M Source/JavaScriptCore/assembler/MacroAssemblerX86_64.h
    M Source/JavaScriptCore/yarr/YarrJIT.cpp

  Log Message:
  -----------
  [JSC] Relanding 280425 at main with tweaks
https://bugs.webkit.org/show_bug.cgi?id=278566
rdar://134575576

Reviewed by David Degazio.

This patch is relanding David's 280425 at main again with some assertions and fixes.

1. higherMatchStart computation was using `<` before. But it should be `<=` since the range's `hi` is included.
2. Use std::span for range computations.
3. Add std::sort explicitly for ranges and matches. We think this is sorted, but we are skeptical about whether we have a case not being sorted.
   To catch that, we also added ASSERT(std::is_sorted) to allow fuzzers etc. to catch these patterns.

Original commit message:

    Changes how YarrJIT handles character class matches via the following:

     1. Optimize single-range checks from two branches into subtract + branch.

     2. Use a bit-vector test to quickly match a set of individual characters,
        as opposed to the current strategy of O(n) sequential equality checks.

     3. Make the logic of matchCharacterClassRange more recursive. We use the
        optimized single-range test if there is only a single range, and use
        the new bit-vector test if the whole set of ranges and character matches
        fits within a small-enough range. Moreover, the binary search is now
        totally recursive, meaning we can use these specialized checks for
        recursive checks within the binary search too, whereas currently binary
        search is kind of all-or-nothing.

     4. A few small optimizations are removed - YarrJIT no longer special-cases
        ASCII letters in character class matches, since character set matching
        is now faster. Turning adjacent character matches into length-two ranges
        is also removed during CharacterClass construction since this doesn't
        really do anything other than make the binary search do extra work (I'd
        be really surprised if this was ever particularly profitable).

    Overall, this seems to be a somewhat modest but appreciable perf win on
    microbenchmarks. On the added ASCII alphanumeric test I'm seeing about 10%
    improvement with this new approach, and on the single-chars test I'm seeing
    more like 20% improvement. I've added a test for a set of separator chars
    too, and we have maybe a small ~2% improvement on my machine - this is pretty
    small and hopefully improvable? Not so exciting, but let's have the
    microbenchmark in the tree anyway.

* JSTests/microbenchmarks/regexp-match-alphanumeric.js: Added.
* JSTests/microbenchmarks/regexp-match-multiple-single-chars.js: Added.
* JSTests/microbenchmarks/regexp-match-separators.js: Added.
(let.src):
(dot):
(test):
(i.let.re):
* Source/JavaScriptCore/assembler/MacroAssembler.h:
(JSC::MacroAssembler::lshiftPtr):
(JSC::MacroAssembler::lshift32):
* Source/JavaScriptCore/assembler/MacroAssemblerARM64.h:
(JSC::MacroAssemblerARM64::lshift32):
(JSC::MacroAssemblerARM64::lshift64):
* Source/JavaScriptCore/assembler/MacroAssemblerARMv7.h:
(JSC::MacroAssemblerARMv7::lshift32):
* Source/JavaScriptCore/assembler/MacroAssemblerRISCV64.h:
(JSC::MacroAssemblerRISCV64::lshift32):
* Source/JavaScriptCore/assembler/MacroAssemblerX86_64.h:
(JSC::MacroAssemblerX86_64::lshift64):
* Source/JavaScriptCore/yarr/YarrJIT.cpp:

Canonical link: https://commits.webkit.org/282671@main



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