Messages in this thread | | | Date | Sat, 9 Nov 2013 00:46:11 -0600 | Subject | Re: [PATCH v2] ARM: Use udiv/sdiv for __aeabi_{u}idiv library functions | From | Matt Sealey <> |
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On Fri, Nov 8, 2013 at 5:00 PM, Stephen Boyd <sboyd@codeaurora.org> wrote: > If we're running on a v7 ARM CPU, detect if the CPU supports the > sdiv/udiv instructions and replace the signed and unsigned > division library functions with an sdiv/udiv instruction. > > Running the perf messaging benchmark in pipe mode > > $ perf bench sched messaging -p > > shows a modest improvement on my v7 CPU. > > before: > (5.060 + 5.960 + 5.971 + 5.643 + 6.029 + 5.665 + 6.050 + 5.870 + 6.117 + 5.683) / 10 = 5.805 > > after: > (4.884 + 5.549 + 5.749 + 6.001 + 5.460 + 5.103 + 5.956 + 6.112 + 5.468 + 5.093) / 10 = 5.538 > > (5.805 - 5.538) / 5.805 = 4.6%
Even with the change to the output constraint suggested by Mans, you get absolutely identical benchmark results? There's a lot of variance in any case..
BTW has there been any evaluation of the penalty for the extra branching, or the performance hit for the ARMv7-without-division cases?
Ta, Matt Sealey <neko@bakuhatsu.net>
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