Hi,  
  
Tim seems to be using a 64 bit VM on the Pi 4. I do not see it on 32 bit VMs on a Pi 3 nor on a Pi 400, so the same hardware.  I do see it on a Arm64 system though.  
  
So it seems, for once, not to be a 32 bit system problem and does seem to be just Arm64.  
  
cheers  
  
bruce  
  
  

> On Sat, May 08, 2021 at 03:25:35PM -0700, tim Rowledge wrote:  
>  > I had to modify Dave's code smidge because #raisedTo: etc get used in the printing of the results of theTranscript>showln: used in ... #raisedToInteger:, which confused things a smidge.  
>  >  
>  > So, renamed to #testRaisedToInteger: -  
>  >  
>  > On Mac 64bit  
>  > TOP LOOP 1 BITPROBE 32  
>  > INNER LOOP 4  
>  > TOP LOOP 4 BITPROBE 16  
>  > INNER LOOP 64  
>  > TOP LOOP 64 BITPROBE 8  
>  > INNER LOOP 16384  
>  > TOP LOOP 16384 BITPROBE 4  
>  > INNER LOOP 1073741824  
>  > TOP LOOP 1073741824 BITPROBE 2  
>  > INNER LOOP 4611686018427387904  
>  > TOP LOOP 4611686018427387904 BITPROBE 1  
>  >  
>  > On Pi4 64bit  
>  >  
>  > TOP LOOP 1 BITPROBE 32  
>  > INNER LOOP 4  
>  > TOP LOOP 4 BITPROBE 16  
>  > INNER LOOP 64  
>  > TOP LOOP 64 BITPROBE 8  
>  > INNER LOOP 16384  
>  > TOP LOOP 16384 BITPROBE 4  
>  > INNER LOOP 1073741824  
>  > TOP LOOP 1073741824 BITPROBE 2  
>  > INNER LOOP 0  
>  > TOP LOOP 0 BITPROBE 1  
>  >  
>  > What we then see is that the Integer>>#digitMultiply:neg: primitive is failing; commenting out the prim gets us the correct answer.  
>  >  
>  > However, to make like that bit more amusing,  
>  > `SmallInteger maxVal squared`  
>  > gives the same answer on both systems (with the prim enabled on Pi 4) so it isn't simply that the largeint plugin is broken overall.  
>  > If I try 16r80000000 squared I *usually* get 0 but once or twice get 4611686018427387904, so clearly something odd is going on. Given that this appears to be platform specific I have to start suspecting something in the ARM64 trampoline code.  
>  >  
>   
>   
>  If the primitive is failing for 16r80000000 squared, then I wonder if we  
>  may be looking at a signed/unsigned arithmetic problem somewhere in the  
>  plugin.  
>   
>  16r80000000 asRegister ==> a TwosComplementRegister with value -2147483648 (10000000000000000000000000000000)  
>   
>  You are running a 32-bit VM on Pi, right? If so, then perhaps the  
>  same failure is happening on other 32-bit VMs but nobody noticed it  
>  until now?  
>   
>  Dave
  

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