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[RegAllocGreedy] IMPLICIT_DEF values shouldn't prefer registers
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Authored by john.brawn on Dec 13 2018, 6:11 AM.

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Summary

It costs nothing to spill an IMPLICIT_DEF value (the only spill code that's generated is a KILL of the value), so when creating split constraints if the live-out value is IMPLICIT_DEF the exit constraint should be DontCare instead of PrefReg.

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rL LLVM

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john.brawn created this revision.Dec 13 2018, 6:11 AM

It looks good to me, but @arsenm could you also take a look?

This revision is now accepted and ready to land.Dec 13 2018, 1:25 PM
This revision was automatically updated to reflect the committed changes.