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2c1b5130aa
This CL adds intrinsics for the 64-bit addition and subtraction functions in math/bits. These intrinsics use the condition code to propagate the carry or borrow bit. To make the carry chains more efficient I've removed the 'clobberFlags' property from most of the load and store operations. Originally these ops did clobber flags when using offsets that didn't fit in a signed 20-bit integer, however that is no longer true. As with other platforms the intrinsics are faster when executed in a chain rather than a loop because currently we need to spill and restore the carry bit between each loop iteration. We may be able to reduce the need to do this on s390x (e.g. by using compare-and-branch instructions that do not clobber flags) in the future. name old time/op new time/op delta Add64 1.21ns ± 2% 2.03ns ± 2% +67.18% (p=0.000 n=7+10) Add64multiple 2.98ns ± 3% 1.03ns ± 0% -65.39% (p=0.000 n=10+9) Sub64 1.23ns ± 4% 2.03ns ± 1% +64.85% (p=0.000 n=10+10) Sub64multiple 3.73ns ± 4% 1.04ns ± 1% -72.28% (p=0.000 n=10+8) Change-Id: I913bbd5e19e6b95bef52f5bc4f14d6fe40119083 Reviewed-on: https://go-review.googlesource.com/c/go/+/174303 Run-TryBot: Michael Munday <mike.munday@ibm.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Cherry Zhang <cherryyz@google.com> |
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