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Will register window mechanism slow down the execution of ecos program for SPARC?


Hi all:
     I just wonder about whether the register windows will slow down the
execution of ecos program.
In sparc each time for context switching the old thread context will be
saved this includes all the regiter windows(because this is done by an
register window overflow trap), even not all register windows have been
already used, consider a situation that just 2 register windows are used but
8 register windows are saved(6 of those are not used). also when restoring
all register windows will be restored (done by register window underflow
trap). Also this happens when a seperate interrupt stack is used. The
purpose of introducing register window is to speed up the calling to an
subfunction, but now in ecos it seems to be an shortcoming compared to other
target without register window for subfunction calling in the context
switching and restoring. maybe I got it wrong then sorry about this. Thanks
a lot.



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