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Resource Constraints
Instruction Set3-26 SPRU733
3.7.8 Constraints on Floating-Point Instructions
If an instruction has a multicycle functional unit latency, it locks the functional
unit for the necessary number of cycles. Any new instruction dispatched to that
functional unit during this locking period causes undefined results. If an
instruction with a multicycle functional unit latency has a condition that is evalu-
ated as false during E1, it still locks the functional unit for subsequent cycles.
An instruction of the following types scheduled on cycle i has the following
constraints:
DP compare No other instruction can use the functional unit on cycles
i and i + 1.
ADDDP/SUBDP No other instruction can use the functional unit on cycles
i and i + 1.
MPYI No other instruction can use the functional unit on cycles
i, i + 1, i + 2, and i + 3.
MPYID No other instruction can use the functional unit on cycles
i, i + 1, i + 2, and i + 3.
MPYDP No other instruction can use the functional unit on cycles
i, i + 1, i + 2, and i + 3.
MPYSPDP No other instruction can use the functional unit on cycles
i and i + 1.
MPYSP2DP No other instruction can use the functional unit on cycles
i and i + 1.
If a cross path is used to read a source in an instruction with a multicycle func-
tional unit latency, you must ensure that no other instructions executing on the
same side uses the cross path.
An instruction of the following types scheduled on cycle i using a cross path
to read a source, has the following constraints:
DP compare No other instruction on the same side can used the cross
path on cycles i and i + 1.
ADDDP/SUBDP No other instruction on the same side can use the cross
path on cycles i and i + 1.
MPYI No other instruction on the same side can use the cross
path on cycles i, i + 1, i + 2, and i + 3.
MPYID No other instruction on the same side can use the cross
path on cycles i, i + 1, i + 2, and i + 3.