7.3.3. Cycle information, for cycle-accurate tracing

For more information about cycle-accurate tracing in ETMv3 see Cycle-accurate tracing.

Cycle-accurate mode enables some trace packets to be traced along with the cycle in which they are generated. Cycle information is output using the following packets:

In addition to giving the cycle count for instruction trace, cycle count information is meaningful for the following packets:

You cannot rely on the cycle count information for other packets. The packets for which cycle count information is not relevant are:

Cycle information can only give cycle information for a particular point in the processor pipeline. In complex processors some stages in the pipeline might be capable of advancing independently of others, with the effect that the number of cycles between instructions is not the same at all points in the pipeline. You must be aware of these limitations when interpreting the cycle information.

I-sync packets might contain a cycle count, but you cannot rely on this count to determine the precise cycle of the I-sync packet. However, if you use the cycle count information with the I-sync, plus the other cycle information produced by P-headers, the cycle accuracy is maintained for instructions and for the other packets for which the cycle count information is meaningful.

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