[PATCH] D39386: [Power9] Allow gpr callee saved spills in prologue to vector registers rather than stack

[Francis Visoiu Mistrih via Phabricator via llvm-commits]

thegameg added inline comments.


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Comment at: lib/Target/PowerPC/PPCFrameLowering.cpp:1990
+            MachineBasicBlock *BB = &*I;
+            BB->addLiveIn(VolatileVFRegNo[i]);
+          }
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syzaara wrote:
> thegameg wrote:
> > I may be missing something, but why is this needed? Won't it be def'd anyway?
> Without this, we will get machine verify errors in the epilogue that we are using an undefined physical register. This can be fixed by adding the register as live into the block. However, adding it to only the epilogue isn't enough since other blocks may clobber the register in between the prologue and epilogue.
Ah, right, I see. There is a function called `updateLiveness` in PrologEpilogInserter, which propagates the liveness of CSRs. You might want to look into that.


https://reviews.llvm.org/D39386