Pipeline Execution of Instruction Types / Functional Unit Constraints

4.2.15 MPYSP2DP Instruction

The MPYSP2DP instruction uses the E1 through E5 phases of the pipeline to complete its operations (see Table 4−17). src1 and src2 are read on E1. The lower 32 bits of the result are written on E4, and the upper 32 bits of the result are written on E5. The MPYSP2DP instruction is executed on the .M unit. The functional unit latency for the MPYSP2DP instruction is 2. Figure 4−27 shows the fetch, decode, and execute phases of the pipeline that the MPYSP2DP instruction uses.

Table 4−17. MPYSP2DP Instruction Execution

Pipeline Stage

E1

E2

E3

E4

E5

 

 

 

 

 

 

Read

src1

 

 

 

 

 

src2

 

 

 

 

Written

 

 

 

dst_l

dst_h

Unit in use

.M

 

 

 

 

 

 

 

 

 

 

Figure 4−27. MPYSP2DP Instruction Phases

PG

PS PW

PR DP

DC

E1

E2

E3

E4

E5

4 delay slots

4.3 Functional Unit Constraints

If you want to optimize your instruction pipeline, consider the instructions that are executed on each unit. Sources and destinations are read and written differently for each instruction. If you analyze these differences, you can make further optimization improvements by considering what happens during the execution phases of instructions that use the same functional unit in each execution packet.

The following sections provide information about what happens during each execute phase of the instructions within a category for each of the functional units.

SPRU733

Pipeline

4-33

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Texas Instruments TMS320C67X/C67X+ DSP manual Functional Unit Constraints, MPYSP2DP Instruction