The <Unknown> Data Object and Its Elements

Under various circumstances, event data can not be mapped to a particular data object. In such cases, the data is mapped to the special data object named <Unknown> and one of its elements as described below.

• Module with trigger PC not compiled with -xhwcprof

  No event-causing instruction or data object was identified because the object code was not compiled with hardware counter profiling support.

• Backtracking failed to find a valid branch target

  No event-causing instruction was identified because the hardware profiling support information provided in the compilation object was insufficient to verify the validity of backtracking.

• Backtracking traversed a branch target

  No event-causing instruction or data object was identified because backtracking encountered a control transfer target in the instruction stream.

• No identifying descriptor provided by the compiler

  Backtracking determined the likely causal memory-referencing instruction, but its associated data object was not specified by the compiler.

• No type information

  Backtracking determined the likely event-causing instruction, but the instruction was not identified by the compiler as a memory-referencing instruction.

• Not determined from the symbolic information provided by the compiler

  Backtracking determined the likely causal memory-referencing instruction, but it was not identified by the compiler and associated data object determination is therefore not possible. Compiler temporaries are generally unidentified.

• Backtracking was prevented by a jump or call instruction

  No event-causing instructions were identified because backtracking encountered a branch or call instruction in the instruction stream.

• Backtracking did not find trigger PC

  No event-causing instructions were found within the maximum backtracking range.

• Could not determine VA because registers changed after trigger instruction

  The virtual address of the data object was not determined because registers were overwritten during hardware counter skid.

• Memory-referencing instruction did not specify a valid VA

  The virtual address of the data object did not appear to be valid.