[DFAPacketizer] Fix large compile-time regression for VLIW targets

D68992 / rL375086 refactored the packetizer and removed a bunch of logic. Unfortunately it creates an Automaton object whenever a DFAPacketizer is required. These objects have no longevity, and in particular on a debug build the population of the Automaton's transition map from the underlying table is very slow (because it is called ~10 times per MachineFunction, in the testcase I'm looking at).

This patch changes Automaton to wrap its underlying constant data in std::shared_ptr, which allows trivial copy construction. The DFAPacketizer creation function now creates a static archetypical Automaton and copies that whenever a new DFAPacketizer is required.

This takes a testcase down from ~20s to ~0.5s in debug mode.

llvm-svn: 375240

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/utils/TableGen/DFAPacketizerEmitter.cpp b/llvm/utils/TableGen/DFAPacketizerEmitter.cpp
index 0d3c6fdc933..ccb4ef1b967 100644
--- a/llvm/utils/TableGen/DFAPacketizerEmitter.cpp
+++ b/llvm/utils/TableGen/DFAPacketizerEmitter.cpp
@@ -538,10 +538,10 @@ void DFAPacketizerEmitter::emitForItineraries(
   OS << "DFAPacketizer *" << SubTargetClassName << "::"
      << "create" << DFAName
      << "DFAPacketizer(const InstrItineraryData *IID) const {\n"
-     << "  Automaton<uint64_t> A(ArrayRef<" << TargetAndDFAName
+     << "  static Automaton<uint64_t> A(ArrayRef<" << TargetAndDFAName
      << "Transition>(" << TargetAndDFAName << "Transitions), "
      << TargetAndDFAName << "TransitionInfo);\n"
-     << "  return new DFAPacketizer(IID, std::move(A));\n"
+     << "  return new DFAPacketizer(IID, A);\n"
      << "\n}\n\n";
 }