Don't break bundles when adding DBG_VALUE

[npjdesres]

Summary

LiveDebugValues should test whether an instruction is within a bundle before inserting a DBG_VALUE instruction.

[davide]

This change has no test associated. Can you please add one?
Also, this patch is oddly formatted, can you please run clang-format on it?

[probinson]

lib/CodeGen/LiveDebugValues.cpp

671

Please add a FIXME to preserve these DBG_VALUEs. I don't know how to do that, but losing them is not great.

[wolfgangp]

lib/CodeGen/LiveDebugValues.cpp

671

I agree with Paul here. The DBG_VALUE instruction should be inserted after the bundle then.

[npjdesres]

Thank you so far, and sorry for the radio silence. I'll work on a testcase and revising this patch, but things just picked up in my office, so it may be next week.

[materi]

lib/CodeGen/LiveDebugValues.cpp

671

But we must not put the DBG_VALUE after the bundle if the bundle also modifies the frame pointer. We recently had such a bug in my out-of-tree back-end.

I think moving a DBG_VALUE will require some analysis to make sure the live range is not moved.

lib/CodeGen/LiveDebugValues.cpp

while (!Worklist.empty()) {
         // examine spill instructions to see whether they spill registers that
         // correspond to user variables.
         for (auto &MI : *MBB)
           OLChanged |= transfer(MI, OpenRanges, OutLocs, VarLocIDs, Spills,
                                 /*transferSpills=*/true);
 
         // Add any DBG_VALUE instructions necessitated by spills.
         for (auto &SP : Spills)
+          if( ! SP.SpillInst->isBundledWithSucc() ) // Don't break bundles.
             MBB->insertAfter(MachineBasicBlock::iterator(*SP.SpillInst),
                              SP.DebugInst);
         Spills.clear();
 
         DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
                                "OutLocs after propagating", dbgs()));
         DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs,
                                "InLocs after propagating", dbgs()));
 
         if (OLChanged) {