[PATCH] D105742: [AMDGPU] Make V_CVT_I32_F64/V_CVT_F64_I32 rematerializable.

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added a comment.

RA has `VirtRegAuxInfo::weightCalcHelper()` function which halves a weight of a LI if it is rematerializable, which in turn leads to different RA decisions. We will generally have a lot of small codegen changes, not just rematerialization instead of spilling:

  // If all of the definitions of the interval are re-materializable,
  // it is a preferred candidate for spilling.
  // FIXME: this gets much more complicated once we support non-trivial
  // re-materialization.
  if (isRematerializable(LI, LIS, VRM, *MF.getSubtarget().getInstrInfo()))
    TotalWeight *= 0.5F;

It may be beneficial to only do it if we have `isAsCheapAsAMove` or at least use a different weight multiplier. This is however a different and much more intrusive change.


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  https://reviews.llvm.org/D105742/new/

https://reviews.llvm.org/D105742