The hand website provides synchronization time for the Cortex-a9 processor .
Link to the manual
For each command (more precisely, I'm talking about the NEON vector instruction), the time is given in the format table shown below (using the VADD instruction as an example):
NAME FORMAT Cycle Source Result Writeback
VADD Dd,Dn,Dm 1 -,2,2 3 6
I understand what the table is trying to say. For example, a Result with a value of 3 means the result of this instruction will be available in cycle 3, and then another instruction depends on the result of this instruction, you can use the result without stopping without problems.
But my question is:
When does this cycle number begin to count? Does he think after the instructions issued?
In addition, as I know, the problem is the step when the instruction is sent to the processor for execution after the command is extracted and decoded, then why are the decoding and sampling cycles not displayed on the table then? This is very important information, since I need to know the extraction and decoding cycles, to be able to know how many cycles I have to wait to execute the instruction smoothly, which depends on the result of the previous instruction.
A clear and accurate answer or a place to find it will be highly appreciated!
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