LLVM Scheduler Target Description

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hi, Recently working on LLVM Target Scheduler Target Description file, I have a question on InstrStage Class.

As shown on Scheduler Tutorial, it says

"/// { 2, x|y, 1 }

/// indicates that the stage occupies either FU x or FU y for 2

/// consecutive cycles and that the next stage starts one cycle

/// after this stage starts. That is, the stage requirements

/// overlap in time."

​If I understood right, this mean that this instruction takes 2 cycles to complete.

After first cycle passes, the another instruction (which has same InstrItinClass name) can be in this stage.

My questions are:

  1. Am I understanding in right way?

  2. What does the FuncUnit means in this case? Does this mean a module such as ALU, FPU?

  3. when I set third operand as 0, this mean the instruction can start simultaneously?

P.S. Always thanks LLVM Community for giving warm kind knowledge.