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Switch statement containing integer constant cases and case bodies just
returning a constant should be optimizable to a simpler and faster table
lookup instead of a jump table.
That is, a switch like this:
switch x {
case 0: return 10
case 1: return 20
case 2: return 30
case 3: return 40
default: return -1
}
Could be optimized to this:
var table = [4]int{10, 20, 30, 40}
if uint(x) < 4 { return table[x] }
return -1
The resulting code is smaller and faster, especially on platforms where
jump tables are not supported.
goos: windows
goarch: arm64
pkg: cmd/compile/internal/test
│ .\old.txt │ .\new.txt │
│ sec/op │ sec/op vs base │
SwitchLookup8Predictable-12 2.708n ± 6% 2.249n ± 5% -16.97% (p=0.000 n=10)
SwitchLookup8Unpredictable-12 8.758n ± 7% 3.272n ± 4% -62.65% (p=0.000 n=10)
SwitchLookup32Predictable-12 2.672n ± 5% 2.373n ± 6% -11.21% (p=0.000 n=10)
SwitchLookup32Unpredictable-12 9.372n ± 7% 3.385n ± 6% -63.89% (p=0.000 n=10)
geomean 4.937n 2.772n -43.84%
Fixes #78203
Change-Id: I74fa3d77ef618412951b2e5c3cb6ebc760ce4ff1
Reviewed-on: https://go-review.googlesource.com/c/go/+/756340
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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This commit is aimed at improving the readability and consistency
of the code base. Extraneous newline characters were present after
some return statements, creating unnecessary separation in the code.
Fixes #64610
Change-Id: Ic1b05bf11761c4dff22691c2f1c3755f66d341f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/548316
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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A future change to gofmt will rewrite
// Doc comment.
//go:foo
to
// Doc comment.
//
//go:foo
Apply that change preemptively to all comments (not necessarily just doc comments).
For #51082.
Change-Id: Iffe0285418d1e79d34526af3520b415a12203ca9
Reviewed-on: https://go-review.googlesource.com/c/go/+/384260
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
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[git-generate]
cd src/cmd/compile/internal/gc
rf '
mv bench_test.go constFold_test.go dep_test.go \
fixedbugs_test.go iface_test.go float_test.go global_test.go \
inl_test.go lang_test.go logic_test.go \
reproduciblebuilds_test.go shift_test.go ssa_test.go \
truncconst_test.go zerorange_test.go \
cmd/compile/internal/test
'
mv testdata ../test
Change-Id: I041971b7e9766673f7a331679bfe1c8110dcda66
Reviewed-on: https://go-review.googlesource.com/c/go/+/279480
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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