5.11. Tracing Java code, ETMv1.3 only

Support for Jazelle state tracing is included in ETMv1.3 or later. A branch into or out of Jazelle state forces a full 5-packet instruction address to be generated. Bit [7] of the fifth address packet indicates the new state of the J-bit. When tracing Java bytes, one or more pipeline status messages might be generated for a particular bytecode, based on the number of interesting loads and stores that occur. Exactly the same number of pipeline status messages is generated if the bytecode is retraced.

TraceEnable is sampled on the first interesting load or store if appropriate, otherwise it is sampled at the end of the bytecode. If TraceEnable is not asserted at this point, tracing is disabled.

ViewData is sampled on the first interesting load or store, and all remaining loads or stores for that bytecode are traced. Each bytecode might therefore result in one or two traced instructions.

Decompression of Java trace in ETMv1 requires a knowledge of the Jazelle architecture, that is confidential. If you want to decompress Java trace, contact ARM Limited for more information.

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