[PATCH] D46232: [SystemZ, IPRA] determineCalleeSaves must always add return register and DP.

[Ulrich Weigand via Phabricator via llvm-commits]

uweigand added a comment.

I do not believe we need to do anything special with https://reviews.llvm.org/source/libunwind/.  This is only special if it is used as frame pointer, in which case the code before already adds it as caller-saved:

  if (HasFP)
    SavedRegs.set(SystemZ::R11D);

I agree we need to handle R14, however.  This is for the scenario where we have a leaf function (so the MFFrame.hasCalls() check will return false), but R14 is still clobbered by some *other* instruction in the current function.  In this case we always need to save and restore it, since the return instruction will implicitly rely on the incoming R14 value.


https://reviews.llvm.org/D46232