From: user5857@newsgrouper.org.invalid   
      
   Stephen Fuld  posted:   
      
   > On 10/29/2025 11:47 AM, MitchAlsup wrote:   
   > >   
   > > BGB  posted:   
   >   
   > snip   
   > >> But, yeah, occasionally dealing with 128-bit data is a major case for 64   
   > >> GPRs and paired-registers registers.   
   > >   
   > > There is always the DBLE pseudo-instruction.   
   > >   
   > >            DBLE   Rd,Rs1,Rs2,Rs3   
   > >   
   > > All DBLE does is to provide more registers for the wide computation   
   > > in such a way that compiler is not forced to pair or share any reg-   
   > > isters. The other thing DBLE does is to tell the decoder that the   
   > > next instruction is 2× as wide as its OpCode states. In lower end   
   > > machines (and in GPUs) DBLE is sequenced as if it were an instruction.   
   > > In higher end machines, DBLE would be CoIssued with its mate.   
   >   
   > So if DBLE says the next instruction is double width, does that mean   
   > that all "128 bit instructions" require 64 bits in the instruction   
   > stream?  So a sequence of say four 128 bit arithmetic instructions would   
   > require the I space of 8 instructions?   
      
   It is a 64-bit machine that provides a small modicum of support for   
   larger sizes. It is not and never will be a 128-bit machine--that is   
   what vVM is for.   
      
   Key words "small modicum"   
      
   DBLE simply supplies registers to the pipeline and width to decode.   
      
   > If so, I guess it is a tradeoff for not requiring register pairing, e.g.   
   > Rn and Rn+1.   
      
   DBLE supports 128-bits in the ISA at the total cost of 1 instruction   
   added per use. In many situations (especially integer) CARRY is the   
   better option because it throws a shadow of width over a number of   
   instructions and thereby has lower code foot print costs. So, a 256   
   bit shift is only 5 instructions instead of 8. And realistically, if   
   you want wider than that, you have already run out of registers.   
      
   --- SoupGate-Win32 v1.05   
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