v8/test/mjsunit/regress/regress-988973.js

// Copyright 2019 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

"".match(/(?:(?=a)b){5}abcde/);
Reland "[regexp] Better quick checks on loop entry nodes" This is a reland of 4b15b984adc63816dff95d78fd1719405116cb89 Updates since original: fix an arithmetic overflow bug, remove an invalid DCHECK, add a unit test that would trigger that DCHECK. Original change's description: > [regexp] Better quick checks on loop entry nodes > > Like the predecessor change https://crrev.com/c/v8/v8/+/1702125 , this > change is inspired by attempting to exit earlier from generated RegExp > code, when no further matches are possible because any match would be > too long. The motivating example this time is the following expression, > which tests whether a string of Unicode playing cards has five of the > same suit in a row: > > /([🂡-🂮]{5})\|([🂱-🂾]{5})\|([🃁-🃎]{5})\|([🃑-🃞]{5})/u > > A human reading this expression can readily see that any match requires > at least 10 characters (5 surrogate pairs), but the LoopChoiceNode for > each repeated option reports its minimum distance to the end of a match > as zero. This is correct, because the LoopChoiceNode's behavior depends > on additional state (the loop counter). However, the preceding node, a > SET_REGISTER action that initializes the loop counter, could confidently > state that it consumes at least 10 characters. Furthermore, when we try > to emit a quick check for that action, we could follow only paths from > the LoopChoiceNode that are possible based on the minimum iteration > count. This change implements both of those "could"s. > > I expect this improvement to apply pretty broadly to expressions that > use minimum repetition counts and that don't meet the criteria for > unrolling. In this particular case, I get about 12% improvement on the > overall UniPoker test, due to reducing the execution time of this > expression by 85% and the execution time of another similar expression > that checks for n-of-a-kind by 20%. > > Bug: v8:9305 > > Change-Id: I319e381743967bdf83324be75bae943fbb5dd496 > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1704941 > Commit-Queue: Seth Brenith <seth.brenith@microsoft.com> > Reviewed-by: Jakob Gruber <jgruber@chromium.org> > Cr-Commit-Position: refs/heads/master@{#62963} Bug: v8:9305 Change-Id: I992070d383009013881bf778242254c27134b650 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1726674 Reviewed-by: Jakob Gruber <jgruber@chromium.org> Commit-Queue: Seth Brenith <seth.brenith@microsoft.com> Cr-Commit-Position: refs/heads/master@{#63009} 2019-07-30 22:13:30 +00:00			`// Copyright 2019 the V8 project authors. All rights reserved.`
			`// Use of this source code is governed by a BSD-style license that can be`
			`// found in the LICENSE file.`

			`"".match(/(?:(?=a)b){5}abcde/);`