[llvm-dev] InstrStage, Interpretation of getUnits()

Pierre-André Saulais via llvm-dev
2015-12-04T22:36:28Z

Hi Rail,

This is a bitfield, each bit represents one functional unit. Unit 0
would be the LSB (1 << 0), unit 1 one bit above LSB (1 << 1),  and
so on
until unit N (1 << N). For example a return value of 9 means that units
0 and 3 are used.

Cheers,
Pierre-Andre

On 04/12/15 22:20, Rail Shafigulin via llvm-dev wrote:
> Here is the code
>
<https://github.com/llvm-mirror/llvm/blob/c68dcdb413079d92118839dbd835e125293f411a/include/llvm/MC/MCInstrItineraries.h#L75>
> for InstrStage::getUnits()
>
> /// \brief Returns the choice of FUs.
> unsigned getUnits() const { return Units_; }
>
> This method returns an integer. How does one interpret it? As far as I
> see it it should tell me what resources are used by a given stage but
> I can't figure out what a return value means. Would anyone care to
help?
>
> Thanks,
>
> --
> Rail Shafigulin
> Software Engineer
> Esencia Technologies
>
>
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