I think that's a result of those add blocks being used in trellises (could be wrong on that assumption).
If we add saturating adds we should follow most architecture conventions and explicitly call it saturating. On Sunday, March 6, 2016, Andy Walls <a...@silverblocksystems.net> wrote: > On Sun, 2016-03-06 at 16:33 -0500, West, Nathan wrote: > > > > > By the way, if you choose to do this please don't be afraid to ask > > questions; this is a pretty well defined problem, but [...] > > Hi Nathan, > > Since you mentioned it, a question popped to my mind: > > The current add_const blocks let integer overflow happen, so that > integer numbers wrap around. In DSP, saturation math is often what is > desired, not overflow. We'd rather the numbers clip at the max or min > value, rather than experience some huge jump. SIMD instruction sets > provide instructions that perform saturation math, e.g. the MMX > intrinsic __m64 _m_paddsw(__m64 a, __m64 b) for adding 4 sets of 16 bit > integers. > > Should the new volk routines, meant to speed up the integer version of > add_const blocks, perform saturation math, or stick with the current > overflow behavior? > > > Cheers, > > > > Nathan > > Regards, > Andy > >
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