Missing Opcode for cm.jt

[JAYANTH-IITM]

Opcode is missing for the cm.jt , which is part of zcmt

[JAYANTH-IITM]

Andrew Waterman (@aswaterman) can you please help here

[aswaterman]

The issue is that they overlap each other in the encoding space. If c_index is less than 32, then it is cm.jt, otherwise, it is cm.jalt.

[JAYANTH-IITM]

yes but in rv_zcmt file only " cm.jalt c_index 1..0=2 15..13=5 12..10=0 is there .
cm.jt , the instr itself is not there.

[aswaterman]

How do you propose to solve the problem? If you just add the instruction, you'll get an overlap error. If you define it as a pseudoinstruction, it will execute correctly, but the description is technically incorrect (since it is not a pseudoinstruction).

[IIITM-Jay]

Andrew Waterman (@aswaterman) To differentiate cm.jt and cm.jalt without overlap, if there is any unused bit or an available spare bit , especially in positions that aren’t strictly defined by the existing cm.jalt encoding, then I think that could be used as a "flag" to differentiate cm.jt from cm.jalt.

But I don't think there is any such available bit to have the above solution to work out. Am I correct?

[aswaterman]

Jay Dev Jha (@IIITM-Jay) Correct, there is no such bit. The logic is that if c_index[7:5] != 0 then it's cm.jalt; otherwise it's cm.jt.