TableGen/GlobalISel: Address fixme

[arsenm]

Summary

Don't call computeAvailableFunctionFeatures for every instruction.

[paquette]

LGTM

[arsenm]

f937b43fdb30b67facf616ad394976b08001ee89

llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h

public:
   ///     for I in all mutated/inserted instructions:
   ///       !isPreISelGenericOpcode(I.getOpcode())
   virtual bool select(MachineInstr &I) = 0;
 
   CodeGenCoverage *CoverageInfo = nullptr;
   GISelKnownBits *KnownBits = nullptr;
   MachineFunction *MF = nullptr;
 
+  virtual void setupGeneratedPerFunctionState(MachineFunction &MF) {
+    llvm_unreachable("TableGen should have emitted implementation");
+  }
+
   /// Setup per-MF selector state.
   virtual void setupMF(MachineFunction &mf,
                        GISelKnownBits &KB,
                        CodeGenCoverage &covinfo) {
     CoverageInfo = &covinfo;
     KnownBits = &KB;
     MF = &mf;
+    setupGeneratedPerFunctionState(mf);
   }
 
 protected:
   using ComplexRendererFns =
       Optional<SmallVector<std::function<void(MachineInstrBuilder &)>, 4>>;
   using RecordedMIVector = SmallVector<MachineInstr *, 4>;
   using NewMIVector = SmallVector<MachineInstrBuilder, 4>;
 

llvm/utils/TableGen/GlobalISelEmitter.cpp

void GlobalISelEmitter::run(raw_ostream &OS) {
   SubtargetFeatureInfoMap FunctionFeatures;
   std::copy_if(SubtargetFeatures.begin(), SubtargetFeatures.end(),
                std::inserter(FunctionFeatures, FunctionFeatures.end()),
                [](const SubtargetFeatureInfoMap::value_type &X) {
                  return X.second.mustRecomputePerFunction();
                });
 
   SubtargetFeatureInfo::emitComputeAvailableFeatures(
-      Target.getName(), "InstructionSelector", "computeAvailableModuleFeatures",
       ModuleFeatures, OS);
 
+
+  OS << "void " << Target.getName() << "InstructionSelector"
+    "::setupGeneratedPerFunctionState(MachineFunction &MF) {\n"
+    "  AvailableFunctionFeatures = computeAvailableFunctionFeatures("
+    "(const " << Target.getName() << "Subtarget*)&MF.getSubtarget(), &MF);\n"
+    "}\n";
+
   if (Target.getName() == "X86" || Target.getName() == "AArch64") {
     // TODO: Implement PGSO.
     OS << "static bool shouldOptForSize(const MachineFunction *MF) {\n";
     OS << "    return MF->getFunction().hasOptSize();\n";
     OS << "}\n\n";
   }
 
   SubtargetFeatureInfo::emitComputeAvailableFeatures(
llvm::stable_sort(Rules, [&](const RuleMatcher &A, const RuleMatcher &B) {
     return false;
   });
 
   OS << "bool " << Target.getName()
      << "InstructionSelector::selectImpl(MachineInstr &I, CodeGenCoverage "
         "&CoverageInfo) const {\n"
      << "  MachineFunction &MF = *I.getParent()->getParent();\n"
      << "  MachineRegisterInfo &MRI = MF.getRegInfo();\n"
-     << "  // FIXME: This should be computed on a per-function basis rather "
-        "than per-insn.\n"
-     << "  AvailableFunctionFeatures = computeAvailableFunctionFeatures(&STI, "
-        "&MF);\n"
      << "  const PredicateBitset AvailableFeatures = getAvailableFeatures();\n"
      << "  NewMIVector OutMIs;\n"
      << "  State.MIs.clear();\n"
      << "  State.MIs.push_back(&I);\n\n"
      << "  if (executeMatchTable(*this, OutMIs, State, ISelInfo"
      << ", getMatchTable(), TII, MRI, TRI, RBI, AvailableFeatures"
      << ", CoverageInfo)) {\n"
      << "    return true;\n"
OS << "#ifdef GET_GLOBALISEL_PREDICATES_DECL\n"
      << "}\n"
      << "PredicateBitset\n"
      << "computeAvailableModuleFeatures(const " << Target.getName()
      << "Subtarget *Subtarget) const;\n"
      << "PredicateBitset\n"
      << "computeAvailableFunctionFeatures(const " << Target.getName()
      << "Subtarget *Subtarget,\n"
      << "                                 const MachineFunction *MF) const;\n"
+     << "void setupGeneratedPerFunctionState(MachineFunction &MF) override;\n"
      << "#endif // ifdef GET_GLOBALISEL_PREDICATES_DECL\n";
 
   OS << "#ifdef GET_GLOBALISEL_PREDICATES_INIT\n"
      << "AvailableModuleFeatures(computeAvailableModuleFeatures(&STI)),\n"
      << "AvailableFunctionFeatures()\n"
      << "#endif // ifdef GET_GLOBALISEL_PREDICATES_INIT\n";
 }