4d10d4ad84
For riscv64/rva22u64 and above, we can intrinsify math/bits.OnesCount
using the CPOP/CPOPW machine instructions. Since the native Go
implementation of OnesCount is relatively expensive, it is also
worth emitting a check for Zbb support when compiled for rva20u64.
On a Banana Pi F3, with GORISCV64=rva22u64:
│ oc.1 │ oc.2 │
│ sec/op │ sec/op vs base │
OnesCount-8 16.930n ± 0% 4.389n ± 0% -74.08% (p=0.000 n=10)
OnesCount8-8 5.642n ± 0% 5.016n ± 0% -11.10% (p=0.000 n=10)
OnesCount16-8 9.404n ± 0% 5.015n ± 0% -46.67% (p=0.000 n=10)
OnesCount32-8 13.165n ± 0% 4.388n ± 0% -66.67% (p=0.000 n=10)
OnesCount64-8 16.300n ± 0% 4.388n ± 0% -73.08% (p=0.000 n=10)
geomean 11.40n 4.629n -59.40%
On a Banana Pi F3, compiled with GORISCV64=rva20u64 and with Zbb
detection enabled:
│ oc.3 │ oc.4 │
│ sec/op │ sec/op vs base │
OnesCount-8 16.930n ± 0% 5.643n ± 0% -66.67% (p=0.000 n=10)
OnesCount8-8 5.642n ± 0% 5.642n ± 0% ~ (p=0.447 n=10)
OnesCount16-8 10.030n ± 0% 6.896n ± 0% -31.25% (p=0.000 n=10)
OnesCount32-8 13.170n ± 0% 5.642n ± 0% -57.16% (p=0.000 n=10)
OnesCount64-8 16.300n ± 0% 5.642n ± 0% -65.39% (p=0.000 n=10)
geomean 11.55n 5.873n -49.16%
On a Banana Pi F3, compiled with GORISCV64=rva20u64 but with Zbb
detection disabled:
│ oc.3 │ oc.5 │
│ sec/op │ sec/op vs base │
OnesCount-8 16.93n ± 0% 29.47n ± 0% +74.07% (p=0.000 n=10)
OnesCount8-8 5.642n ± 0% 5.643n ± 0% ~ (p=0.191 n=10)
OnesCount16-8 10.03n ± 0% 15.05n ± 0% +50.05% (p=0.000 n=10)
OnesCount32-8 13.17n ± 0% 18.18n ± 0% +38.04% (p=0.000 n=10)
OnesCount64-8 16.30n ± 0% 21.94n ± 0% +34.60% (p=0.000 n=10)
geomean 11.55n 15.84n +37.16%
For hardware without Zbb, this adds ~5ns overhead, while for hardware
with Zbb we achieve a performance gain up of up to 11ns. It is worth
noting that OnesCount8 is cheap enough that it is preferable to stick
with the generic version in this case.
Change-Id: Id657e40e0dd1b1ab8cc0fe0f8a68df4c9f2d7da5
Reviewed-on: https://go-review.googlesource.com/c/go/+/660856
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>
Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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