[PATCH] D33562: MachineLICM: Add new condition for hoisting of caller preserved registers

[Matthias Braun via Phabricator via llvm-commits]

MatzeB added a comment.

Instead of introducing yet another target callback, how about some simple heuristic like `MRI.hasOneDef(Reg) && !MRI.getUsedPhysRegsMask().test(Reg)`[1] allowing hoisting up to the point of that definition (which you can find out with `MRI.def_instr_begin(Reg)` or similar).

[1] We really oughta rename UsedPhysRegMask to something that makes sense (it's simply the union of call regmask operands in the function).


https://reviews.llvm.org/D33562