pseudocode suggests that replaced sequence is longer than necessary

[jnk0le]

The pseudocode suggest as if the proposed instructions were replacing 4 instruction sequence:

    beqz rs2, 1f
    mv rd, rs1
    j 2f
1:
    mv rd, zero
2:

even though it can be implemented in 3 instructions:

    mv rd, zero
    beqz rs2, 1f
    mv rd, rs1
1:

Of course it doesn't reflect exactly what those instructions are doing, but there is nowhere any mention about the sequence those instructions replace, so the pseudocode defacto takes its role.

[ptomsich]

This pseudocode is intended to clarify the semantic dependencies on the input operands: the zero-result is predictable from the value of $rs2.

Also note that the shorter sequence proposed does not work for regno(rd) == regno(rs1).

[ptomsich]

/close

[jnk0le]

Also note that the shorter sequence proposed does not work for regno(rd) == regno(rs1).

then the inverted sequence should work:

    mv rd, rs1
    bnez rs2, 1f
    mv rd, zero
1:

but in case of regno(rd) == regno(rs1) compilers would emit 2 instruction sequence instead:

    bnez rs2, 1f
    mv rd, zero
1:

I think that "equivalent sequences" could be covered by other chapter. Table in 2.1 is a one good place.