From: cross@spitfire.i.gajendra.net   
      
   In article ,   
   John Dallman  wrote:   
   >In article <10c32cu$ahp$2@reader2.panix.com>,   
   >cross@spitfire.i.gajendra.net (Dan Cross) wrote:   
   >   
   >> Most ARM64 cores also support A32 and T32   
   >   
   >That is changing, reasonably quickly. ARM stopped releasing new cores   
   >that could do A32 or T32 in 2023, having been phasing them out since 2021.   
   >Apple's recent cores and Qualcomm's Oryons are likewise 64-bit only.   
      
   I thought I had heard something to that effect.   
      
   I wonder if this suggests that they'll introduce a compressed   
   instruction set a la Thumb for 64 bit mode; -M profile seems to   
   top out at ARMv8.1; and according to the ARMv8-M ARM, only   
   supports T32.  Presumably at some point they'll introduce an   
   ARMv9 core for the embedded market and this will become an   
   issue.   
      
   Or maybe they won't.  We could be in a world of 32-bit embedded   
   cores in that space for a very long time indeed.   
      
   >> but if Windows is only using A64 it doesn't matter.   
   >   
   >Microsoft supply compilers that can target 32-bit code, and run-time   
   >libraries for 32-bit programs. I've never tried building anything on ARM   
   >Windows for 32-bit so I don't know how well they work. I don't know if   
   >ARM Windows 11, which is always a 64-bit OS, will notice that the   
   >hardware is incapable of running A32/T32, but I hope to have appropriate   
   >hardware fairly soon.   
      
   Interesting.  I'm curious how that experiment ends.   
      
   I was also curious how code density stacks up.  Waterman's   
   dissertation has a chart comparing RV64C to other 64-bit ISAs,   
   and A64 is about 25% less dense than RV64C.   
   (https://people.eecs.berkeley.edu/~krste/papers/EECS-2016-1.pdf,   
   page 62)   
      
   I don't see a particularly good comparison against 32-bit ISAs,   
   though.   
      
   	- Dan C.   
      
   --- SoupGate-Win32 v1.05   
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