MMIX Instruction Set
Content
Branches
Name:| BZ $X,YZ | PBZ $X,YZ | (Probable) Branch if zero |
| BNZ $X,YZ | PBNZ $X,YZ | (Probable) Branch if nonzero |
| BN $X,YZ | PBN $X,YZ | (Probable) Branch if negative |
| BNN $X,YZ | PBNN $X,YZ | (Probable) Branch if nonnegative |
| BP $X,YZ | PBP $X,YZ | (Probable) Branch if positive |
| BNP $X,YZ | PBNP $X,YZ | (Probable) Branch if nonpositive |
| BOD $X,YZ | PBOD $X,YZ | (Probable) Branch if odd |
| BEV $X,YZ | PBEV $X,YZ | (Probable) Branch if even |
Specification:
With RA ← @+4*YZ for forward branches
and RA ← @+4*(YZ-216) for backward branches, we have:
| BZ: @ | ← RA, | if s($X) = 0 |
| BNZ:@ | ← RA, | if s($X)≠0 |
| BN: @ | ← RA, | if s($X) < 0 |
| BNN:@ | ← RA, | if s($X) ≥ 0 |
| BP: @ | ← RA, | if s($X) > 0 |
| BNP: @ | ← RA, | if s($X) ≤ 0 |
| BOD: @ | ← RA, | if s($X) mod 2 = 1, d.h. s($X) odd |
| BEV: @ | ← RA, | if s($X) mod 2 = 0, d.h. s($X) even |
Timing:
1υ, in case the branch prediction logic makes a correct prediction (good guess), and 3υ otherwise (bad guess).
Description:
Conditional Branches. The assembler determines automatically, whether the branch is forward or backward and chooses the appropriate instruction. Probable branches, with the prefix "P" are a hint for the processor that the branch is probably taken, directing the instruction fetch to the target address.
See also:
