From: joemonk64@gmail.com   
      
   On Monday, August 23, 2021 at 7:50:23 PM UTC-5, muta...@gmail.com wrote:   
   > On Tuesday, August 24, 2021 at 3:34:40 AM UTC+10, Joe Monk wrote:    
   >    
   > > > Its not possible. RX instruction format only allows 12 bits for the   
   displacement... to keep things in a 4K page :)    
   > > >    
   > > > You can write single CSECT programs today. Nothing stopping that.    
   > > >    
   > > RXY is the instruction format for 20-bit displacements...   
   > Which allows a 1 MiB CSECT, right?    
   >    
   > If you exceed 1 MiB, what do you do? New base    
   > registers, same as you would do for RX instructions?    
   >    
   > Regardless, the idea would be to have a register    
   > dedicated to a less than 1 MiB data section, right?    
   >    
   > And what executable formats do this?    
   >    
   > Thanks. Paul.   
      
   From z/arch pop:   
      
   The long-displacement facility provides a 20-bit signed-displacement field in   
   69 previously existing instructions (by using a previously unused byte in the   
   instructions) and 44 new instructions. A 20-bit signed displacement allows   
   relative addressing of    
   up to 524,287 bytes beyond the location designated by a base register or   
   base-and-index-register pair and up to 524,288 bytes before that location. The   
   enhanced previously existing instructions generally are ones that handle   
   64-bit binary integers. The    
   new instructions generally are new versions of instructions for 32-bit binary   
   integers. The new instructions also include (1)a LOAD BYTE instruction that   
   sign- extends a byte from storage to form a 32-bit or 64-bit result in a   
   general register and (2)    
   new floating-point LOAD and STORE instructions. The long-displace- ment   
   facility provides register-constraint relief by reducing the need for base   
   registers, code size reduction by allowing fewer instructions to be used, and   
   additional improved    
   performance through removal of possible address-generation interlocks.   
      
   Joe   
      
   --- SoupGate-Win32 v1.05   
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