Static branch predictors ?

Tim Frink <>
Tue, 4 Mar 2008 14:32:13 +0000 (UTC)

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Static branch predictors ? (Tim Frink) (2008-03-04)
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From: Tim Frink <>
Newsgroups: comp.compilers
Date: Tue, 4 Mar 2008 14:32:13 +0000 (UTC)
Organization: CS Department, University of Dortmund, Germany
Keywords: optimize, question
Posted-Date: 04 Mar 2008 09:35:05 EST


Many of today's DSPs do not use a dynamic branch prediction but a
static one due to energy efficacy and predictability reasons. The
predicted outcome of a jump depends on the instruction, i.e. a 16-bit
conditional jump instruction is predicted as taken while a 32-bit
instruction with a forward displacement is predicted as not taken.

If the outcome of a jump would be known in advance, one could use the
appropriate jump instructions to avoid misprediction, thus
accelerating the program execution. I assume that profiling data could
be used for that to figure out the more probable jump behavior.

This idea is probably not new, so I wonder if you know any
compilers/optimizers that apply this technique? Do you have own
experiences or know any papers/reports where any results are

[I'm pretty sure that Multiflow did branch prediction in profile
feedback in the 1980s. -John]

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