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192b675f17
On amd64 ReverseBytes16 is lowered to a rotate instruction. However arm64 doesn't
have 16-bit rotate instruction, but has a REV16W instruction which can be used
for ReverseBytes16. This CL adds a rule to turn the patterns like (x<<8) | (x>>8)
(the type of x is uint16, and "|" can also be "^" or "+") to a REV16W instruction.
Code:
func reverseBytes16(i uint16) uint16 { return bits.ReverseBytes16(i) }
Before:
0x0004 00004 (test.go:6) MOVHU "".i(FP), R0
0x0008 00008 ($GOROOT/src/math/bits/bits.go:262) UBFX $8, R0, $8, R1
0x000c 00012 ($GOROOT/src/math/bits/bits.go:262) ORR R0<<8, R1, R0
0x0010 00016 (test.go:6) MOVH R0, "".~r1+8(FP)
0x0014 00020 (test.go:6) RET (R30)
After:
0x0000 00000 (test.go:6) MOVHU "".i(FP), R0
0x0004 00004 (test.go:6) REV16W R0, R0
0x0008 00008 (test.go:6) MOVH R0, "".~r1+8(FP)
0x000c 00012 (test.go:6) RET (R30)
Benchmarks:
name old time/op new time/op delta
ReverseBytes-224 1.000000ns +- 0% 1.000000ns +- 0% ~ (all equal)
ReverseBytes16-224 1.500000ns +- 0% 1.000000ns +- 0% -33.33% (p=0.000 n=9+10)
ReverseBytes32-224 1.000000ns +- 0% 1.000000ns +- 0% ~ (all equal)
ReverseBytes64-224 1.000000ns +- 0% 1.000000ns +- 0% ~ (all equal)
Change-Id: I87cd41b2d8e549bf39c601f185d5775bd42d739c
Reviewed-on: https://go-review.googlesource.com/c/157757
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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The test directory contains tests of the Go tool chain and runtime. It includes black box tests, regression tests, and error output tests. They are run as part of all.bash.
To run just these tests, execute:
../bin/go run run.go
Standard library tests should be written as regular Go tests in the appropriate package.
The tool chain and runtime also have regular Go tests in their packages. The main reasons to add a new test to this directory are:
- it is most naturally expressed using the test runner; or
- it is also applicable to
gccgoand other Go tool chains.