[LLVMdev] Scheduling with RAW hazards
fraser at codeplay.com
Thu May 9 04:02:25 PDT 2013
I have an instruction that takes no operands, and produces two results,
in two consecutive cycles.
I tried both of the following to my Schedule.td file:
InstrItinData<IIMyInstr, [InstrStage<2, [FuncU]>], [1, 2]>,
InstrItinData<IIMyInstr, [InstrStage<1, [FuncU]>, InstrStage<1,
[FuncU]>], [1, 2]>,
From what I can see in examples, these say that the first operand is
ready the cycle after issue, and the second is ready 2 cycles after issue.
But when I issue an instruction that uses both results, it does not obey
this hazard, and is issued the cycle immediately after. Are there any
target hooks I need to implement to get this scheduling correctly?
I noticed that my target was using the default HazardRecognizer, which
is effectively disabled, so I changed it to use the
ScoreboardHazardRecognizer instead. I'm also still using the
SelectionDAG scheduler, but will need to change to the MI scheduler at
some point, to keep up with trunk. Should either of these help?
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