3. Basic extensions

3.1 RV64I basic instruction set

The 64-bit version for integer data, called RV64I, defines a 64-bit version, where registers x0 to x31 and the program counter have 64 bits and 64-bit addresses can be used.

Instructions defined for RV32I now operate on 64-bit data.

Twelve additional instructions can be used to manipulate 32-bit data:

• three arithmetic instructions (addw, addwi, subw) with sign extension on the 32 most significant bits;

• the three shift operations according to the contents of a register and three shift operations according to an immediate ;

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