gdb: MIPS Register packet Format

 
 E.5.2.1 MIPS Register Packet Format
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 The following 'g'/'G' packets have previously been defined.  In the
 below, some thirty-two bit registers are transferred as sixty-four bits.
 Those registers should be zero/sign extended (which?)  to fill the space
 allocated.  Register bytes are transferred in target byte order.  The
 two nibbles within a register byte are transferred most-significant -
 least-significant.
 
 MIPS32
      All registers are transferred as thirty-two bit quantities in the
      order: 32 general-purpose; sr; lo; hi; bad; cause; pc; 32
      floating-point registers; fsr; fir; fp.
 
 MIPS64
      All registers are transferred as sixty-four bit quantities
      (including thirty-two bit registers such as 'sr').  The ordering is
      the same as 'MIPS32'.