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Table
disp<15:14> | Meaning | Predicted | Prediction | |
Target<15:0> | Stack Action | |||
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00 | JMP | PC + {4*disp<13:0>} | – | |
01 | JSR | PC + {4*disp<13:0>} | Push PC | |
10 | RET | Prediction stack | Pop | |
11 | JSR_COROUTINE | Prediction stack | Pop, push PC | |
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The design in Table
Note that the above information is used only as a hint; correct setting of these bits can improve performance but is not needed for correct operation. See Section A.2.2 for more information on branch prediction.
An unconditional long jump can be performed by:
JMP R31,(Rb),hint
Coroutine linkage can be performed by specifying the same register in both the Ra and Rb operands. When disp<15:14> equals ‘10’ (RET) or ‘11’ (JSR_COROUTINE) (that is, the tar- get address prediction, if any, would come from a predictor implementation stack), then bits <13:0> are reserved for software and must be ignored by all implementations. All encodings for bits <13:0> are used by Compaq software or Reserved to Compaq, as follows:
Encoding | Meaning |
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000016 | Indicates |
000116 | Indicates procedure return |
| All other encodings are reserved to Compaq. |
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Instruction Descriptions