cde6a675bc
While profiling parsing, I noticed that scanIdentifier was extremely hot, and could be optimized: it is responsible for a significant fraction of scanning and had a lot of unnecessary branching, bounds checks, and function calls. This CL implements some of those optimizations, while trying to strike a balance between optimization and readability. It achieves this by optimizing for the common case of ASCII identifiers, falling back on the slower scan when encountering the first non-ASCII character. Benchmark results: name old time/op new time/op delta Scan-12 16.9µs ± 4% 15.8µs ± 5% -6.92% (p=0.000 n=20+18) ScanFiles/go/types/expr.go-12 793µs ± 4% 672µs ± 6% -15.23% (p=0.000 n=20+20) ScanFiles/go/parser/parser.go-12 1.08ms ± 6% 0.90ms ± 4% -16.68% (p=0.000 n=20+20) ScanFiles/net/http/server.go-12 1.44ms ± 4% 1.23ms ± 5% -14.58% (p=0.000 n=18+20) ScanFiles/go/scanner/errors.go-12 40.7µs ± 2% 32.6µs ± 3% -20.01% (p=0.000 n=19+20) Change-Id: If78380004248e3ea75cfc78eb7f38f528124dced Reviewed-on: https://go-review.googlesource.com/c/go/+/308611 Trust: Robert Findley <rfindley@google.com> Trust: Robert Griesemer <gri@golang.org> Run-TryBot: Robert Findley <rfindley@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org> |
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