On 26.08.2019 14:08, Anders Magnusson wrote: > Hi all, > > I have been looking at some VAX problems lately, and have found out that > there are two architectural things things that probably would help VAX > quite much. > > 1) Change calling convention. > As described in my previous mail, it would solve a very old > well-known performance problem. > What is this change about? Also if we change ABI we could spare one register to TLS. > 2) Make VAX use IEEE floats :-) > Today virtually no floating point exist that is not IEEE. The only > fragment around is probably the VAX floats. > > I have done some checking, and if we accept the difference in > rounding (VAX uses a different way than IEEE) then it would be (almost) > no overhead in the common cases (overhead comes when dealing with INF, > NAN and subnormals). Can VAX support INF, NaN and subnormals? > - Use F and G floats. They have the same format as IEEE single and > double, and are both available on virtually all VAXen. > - Make use of the floating point faults that VAXen can generate to > emulate the features missing on VAX. > > ...in theory also H floats could be used as long double since they > match the IEEE 128-bit quad precision :-) > But since H float is optional it might end up being emulated > (maybe not a big problem?) > > Comments on this? > Do you mean F for float, G for double, H for long double? If that can work, it sounds fine. > -- Ragge
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