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'.