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9.34.1.2 Register Names

The OpenRISC register file contains 32 general purpose registers.

• The 32 general purpose registers are referred to as ‘rn’.
• The stack pointer register ‘r1’ can be referenced using the alias ‘sp’.
• The frame pointer register ‘r2’ can be referenced using the alias ‘fp’.
• The link register ‘r9’ can be referenced using the alias ‘lr’.

Floating point operations use the same general purpose registers. The instructions lf.itof.s (single precision) and lf.itof.d (double precision) can be used to convert integer values to floating point. Likewise, instructions lf.ftoi.s (single precision) and lf.ftoi.d (double precision) can be used to convert floating point to integer.

OpenRISC also contains privileged special purpose registers (SPRs). The SPRs are accessed using the l.mfspr and l.mtspr instructions.