289567 2025-03-11 14:39:38 -0700 [Yarr] Improve processing of adjacent or near adjacent single characters 2025-03-31 12:40:08 -0700 1 1 1 Unclassified WebKit JavaScriptCore Other Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 msaboff msaboff webkit-bug-importer oldest_to_newest 2102338 0 msaboff 2025-03-11 14:39:38 -0700 There currently is an optimization in the Yarr JIT where we process adjacent single character atoms. For example, /abcd/ is processed as: 1:Term PatternCharacter checked-offset:(4) 'a' <44> 0x12f018b6c: sub x17, x0, #4 <48> 0x12f018b70: ldr w17, [x17, x1] <52> 0x12f018b74: movz w16, #0x6261 <56> 0x12f018b78: movk w16, #0x6463, lsl #16 -> 0x64636261 <60> 0x12f018b7c: cmp w17, w16 <64> 0x12f018b80: b.ne 0x12f018b90 -> <80> 2:Term PatternCharacter checked-offset:(4) 'b' already handled 3:Term PatternCharacter checked-offset:(4) 'c' already handled 4:Term PatternCharacter checked-offset:(4) 'd' already handled but if there is something in between we could check characters that a nearly adjacent individually. For example, /a\dbc/ is currently processed as: 1:Term PatternCharacter checked-offset:(4) 'a' <84> 0x12f015054: sub x17, x0, #4 <88> 0x12f015058: ldrb w6, [x17, x1] <92> 0x12f01505c: cmp w6, #97 <96> 0x12f015060: b.ne 0x12f015098 -> <152> 2:Term PatternCharacter checked-offset:(4) 'b' <100> 0x12f015064: sub x17, x0, #2 <104> 0x12f015068: ldrh w6, [x17, x1] <108> 0x12f01506c: movz w16, #0x6362 -> 25442 <112> 0x12f015070: cmp w6, w16 <116> 0x12f015074: b.ne 0x12f015098 -> <152> 3:Term PatternCharacter checked-offset:(4) 'c' already handled 4:Term PatternCharacterClass checked-offset:(4) <digits> ... Note that we have an existing optimization to move the matching of character classes to after single character atoms. For the second case, we could load 4 characters and mask out the character class character like: 1:Term PatternCharacter checked-offset:(4) 'a' <84> 0x12f014f54: sub x17, x0, #4 <88> 0x12f014f58: ldr w6, [x17, x1] <92> 0x12f014f5c: and w6, w6, #0xffff00ff <96> 0x12f014f60: movz w16, #0x61 <100> 0x12f014f64: movk w16, #0x6362, lsl #16 -> 0x63620061 <104> 0x12f014f68: cmp w6, w16 <108> 0x12f014f6c: b.ne 0x12f014f90 -> <144> 2:Term PatternCharacter checked-offset:(4) 'b' already handled 3:Term PatternCharacter checked-offset:(4) 'c' already handled 4:Term PatternCharacterClass checked-offset:(4) <digits> ... This eliminating a load, compare and branch. The more general case is to use larger load, compare and branch code sequences for single character atoms, including patterns that have mixed in single character width character class atoms. 2102339 1 webkit-bug-importer 2025-03-11 14:40:17 -0700 <rdar://problem/146795365> 2102355 2 msaboff 2025-03-11 15:28:33 -0700 Pull request: https://github.com/WebKit/WebKit/pull/42284 2102491 3 ews-feeder 2025-03-12 01:38:01 -0700 Committed 292003@main (1e14cbbdc2f5): <https://commits.webkit.org/292003@main> Reviewed commits have been landed. Closing PR #42284 and removing active labels. 2107517 4 ews-feeder 2025-03-31 12:40:08 -0700 Committed 289651.362@safari-7621-branch (b78009996aa0): <https://commits.webkit.org/289651.362@safari-7621-branch> Reviewed commits have been landed. Closing PR #2897 and removing active labels.