9711289d06
The change is made since for switch statements with lots of cases, where each case is a constant integer, the emitted bytecode is still a series of jumps, when we can instead use a jump table. If there are 6 or more cases (similar to GCC) of Smi literals, and if the max Smi case minus the min Smi case is not more than 3 times the number of cases, we use a jump table up front to handle Smi's, and then use traditional if-else logic for the rest of the cases. We then use the jump table in interpreter/bytecode-jump-table to do the optimization. This tries to go off issue 9738 in v8's issue tracker. It is not exactly the same, since that recommends doing the work at JIT-time, but has similar ideas. It also partially goes off issue 10764. Bug: v8:9738 Change-Id: Ic805682ee3abf9ce464bb733b427fa0c83a6e10c Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2904926 Reviewed-by: Leszek Swirski <leszeks@chromium.org> Commit-Queue: Leszek Swirski <leszeks@chromium.org> Cr-Commit-Position: refs/heads/master@{#75323}
30 lines
761 B
JavaScript
30 lines
761 B
JavaScript
// Copyright 2017 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// running on old version takes approximately 50 seconds, so 50,000 milliseconds
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new BenchmarkSuite('Big-Switch', [50000], [
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new Benchmark('Big-Switch', false, false, 0, BigSwitch),
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]);
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function BigSwitch() {
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"use strict";
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const n = 100000;
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const c = (a, b) => Array(a).fill().map((a, c) => b(c));
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Function('n, c',
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`
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const a = c(n, a => a);
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let ctr = 0;
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for(let i = 0; i !== (1+n); i++){
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switch(i){
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${c(n, a => `case ${a}: ctr += i; break;`).join('\n')}
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default: ctr += i; break;
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}
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}
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return ctr;
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`)(n,c);
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}
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