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

[Ulrich Weigand via Phabricator via llvm-commits]

uweigand added a comment.

This looks like a generic problem to me, many platforms have registers that are reserved only in some functions but not others.   If function A where a register is reserved calls function B where the register is not reserved, something must ensure that the register is preserved across the call to B.  Usually, this is the case because such registers need to be callee-saved.  But if function B is optimized via IPRA to not save the register, we have a problem ...

Can you check how this is solved on other platforms?  I guess X86 likewise should use a conditionally-reserved register as frame pointer ...


https://reviews.llvm.org/D46232