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Josh Bleecher Snyder 1c4e9b2eda cmd/compile: improve equality algs for arrays of strings
type T [8]string

Prior to this change, we generated this equality algorithm for T:

func eqT(p, q *T) (r bool) {
    for i := range *p {
        if p[i] == q[i] {
		} else {
            return
        }
    }
    return true
}

This change splits this into two loops, so that we can do the
cheap (length) half early and only then do the expensive (contents) half.

We now generate:

func eqT(p, q *T) (r bool) {
    for i := range *p {
        if len(p[i]) == len(q[i]) {
        } else {
            return
        }
    }
    for j := range *p {
        if runtime.memeq(p[j].ptr, q[j].ptr, len(p[j])) {
        } else {
            return
        }
    }
    return true
}

The generated code is typically ~17% larger because it contains
two loops instead of one. In the future, we might want to unroll
the first loop when the array is small.

Change-Id: I26b2793b90ec6aff21766a411b15a4ff1096c03f
Reviewed-on: https://go-review.googlesource.com/c/go/+/230209
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
2020-04-27 17:20:00 +00:00
.github .github: add link to questions in ISSUE_TEMPLATE 2020-01-06 17:05:31 +00:00
api all: remove scattered remnants of darwin/386 2020-04-08 18:37:38 +00:00
doc os, net: define and use os.ErrDeadlineExceeded 2020-04-25 00:26:48 +00:00
lib/time time/tzdata: new package 2020-04-14 19:34:31 +00:00
misc cmd/cgo: use consistent tag for a particular struct 2020-04-14 18:59:37 +00:00
src cmd/compile: improve equality algs for arrays of strings 2020-04-27 17:20:00 +00:00
test cmd/compile: optimize Move with all-zero ro sym src to Zero 2020-04-24 23:58:10 +00:00
.gitattributes build: force all Windows batch files to CRLF 2020-03-22 08:42:38 +00:00
.gitignore
AUTHORS A: Qais Patankar (individual CLA) 2020-04-25 23:01:43 +00:00
CONTRIBUTING.md
CONTRIBUTORS A+C: add Andy Pan (individual CLA) 2020-04-05 22:58:00 +00:00
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SECURITY.md SECURITY.md: update go versions 2019-09-26 15:34:57 +00:00

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