diff options
Diffstat (limited to 'lib/CodeGen')
| -rw-r--r-- | lib/CodeGen/RegisterCoalescer.cpp | 25 |
1 files changed, 18 insertions, 7 deletions
diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp index 30997c24ba..db117ed1a0 100644 --- a/lib/CodeGen/RegisterCoalescer.cpp +++ b/lib/CodeGen/RegisterCoalescer.cpp @@ -988,20 +988,31 @@ bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) { return true; } - // If they are already joined we continue. - if (CP.getSrcReg() == CP.getDstReg()) { - DEBUG(dbgs() << "\tCopy already coalesced.\n"); + // Eliminate undefs. + if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) { + DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n"); LIS->RemoveMachineInstrFromMaps(CopyMI); CopyMI->eraseFromParent(); return false; // Not coalescable. } - // Eliminate undefs. - if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) { - DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n"); + // Coalesced copies are normally removed immediately, but transformations + // like removeCopyByCommutingDef() can inadvertently create identity copies. + // When that happens, just join the values and remove the copy. + if (CP.getSrcReg() == CP.getDstReg()) { + LiveInterval &LI = LIS->getInterval(CP.getSrcReg()); + DEBUG(dbgs() << "\tCopy already coalesced: " << LI << '\n'); + LiveRangeQuery LRQ(LI, LIS->getInstructionIndex(CopyMI)); + if (VNInfo *DefVNI = LRQ.valueDefined()) { + VNInfo *ReadVNI = LRQ.valueIn(); + assert(ReadVNI && "No value before copy and no <undef> flag."); + assert(ReadVNI != DefVNI && "Cannot read and define the same value."); + LI.MergeValueNumberInto(DefVNI, ReadVNI); + DEBUG(dbgs() << "\tMerged values: " << LI << '\n'); + } LIS->RemoveMachineInstrFromMaps(CopyMI); CopyMI->eraseFromParent(); - return false; // Not coalescable. + return true; } // Enforce policies. |