[TableGen] Emit separate computeRequiredFeatures() function

[kpdev42]

Summary

A function is already emitted in *GenInstrInfo.inc that takes Opcode
number and a set of supported Features and reports fatal error if some
of the required features are missing.

The information about features required by the particular opcode can be
reused by llvm-exegesis, so move its computation info a separate
computeRequiredFeatures() function. Then verifyInstructionPredicates()
can just compare the sets of available and required features computed by
the other functions.

This commit moves the definition of FeatureBitsets[] as well as CEFBS_*
enumerator values (that are indices into FeatureBitsets[] array) inside
the computeRequiredFeatures() function because these are implementation
details of that function. The inclusion of potentially huge
computeRequiredFeatures() function is now controlled by a dedicated
macro that is set for simplicity by TableGen-erated code itself if
defined(ENABLE_INSTR_PREDICATE_VERIFIER) && !defined(NDEBUG).

~~

Huawei RRI, OS Lab

[courbet]

llvm/utils/TableGen/InstrInfoEmitter.cpp

748

Won't this force emitting a copy in each compilation unit that includes the generated file ? Using inline instead would allow deduping the symbol.

[kpdev42]

Address review comment

[kpdev42]

llvm/utils/TableGen/InstrInfoEmitter.cpp

748

Changed (here and in computeRequiredFeatures)

llvm/utils/TableGen/InstrInfoEmitter.cpp

 }
 
 void InstrInfoEmitter::emitFeatureVerifier(raw_ostream &OS,
                                            const CodeGenTarget &Target) {
   const auto &All = SubtargetFeatureInfo::getAll(Records);
   std::map<Record *, SubtargetFeatureInfo, LessRecordByID> SubtargetFeatures;
   SubtargetFeatures.insert(All.begin(), All.end());
 
-  OS << "#ifdef ENABLE_INSTR_PREDICATE_VERIFIER\n"
-     << "#undef ENABLE_INSTR_PREDICATE_VERIFIER\n"
-     << "#include <sstream>\n\n";
-
-  OS << "namespace llvm {\n";
-  OS << "namespace " << Target.getName() << "_MC {\n\n";
+  OS << "#if defined(ENABLE_INSTR_PREDICATE_VERIFIER) && !defined(NDEBUG)\n"
+     << "#define GET_COMPUTE_FEATURES\n"
+     << "#endif\n";
+  OS << "#ifdef GET_COMPUTE_FEATURES\n"
+     << "#undef GET_COMPUTE_FEATURES\n"
+     << "namespace llvm {\n"
+     << "namespace " << Target.getName() << "_MC {\n\n";
 
   // Emit the subtarget feature enumeration.
   SubtargetFeatureInfo::emitSubtargetFeatureBitEnumeration(SubtargetFeatures,
                                                            OS);
-
-  // Emit the name table for error messages.
-  OS << "#ifndef NDEBUG\n";
-  SubtargetFeatureInfo::emitNameTable(SubtargetFeatures, OS);
-  OS << "#endif // NDEBUG\n\n";
-
   // Emit the available features compute function.
+  OS << "static ";
   SubtargetFeatureInfo::emitComputeAssemblerAvailableFeatures(
       Target.getName(), "", "computeAvailableFeatures", SubtargetFeatures, OS);
 
   std::vector<std::vector<Record *>> FeatureBitsets;
   for (const CodeGenInstruction *Inst : Target.getInstructionsByEnumValue()) {
     FeatureBitsets.emplace_back();
     for (Record *Predicate : Inst->TheDef->getValueAsListOfDefs("Predicates")) {
       const auto &I = SubtargetFeatures.find(Predicate);
for (auto Pair : zip(A, B)) {
       if (std::get<0>(Pair)->getName() > std::get<1>(Pair)->getName())
         return false;
     }
     return false;
   });
   FeatureBitsets.erase(
       std::unique(FeatureBitsets.begin(), FeatureBitsets.end()),
       FeatureBitsets.end());
-  OS << "#ifndef NDEBUG\n"
-     << "// Feature bitsets.\n"
-     << "enum : " << getMinimalTypeForRange(FeatureBitsets.size()) << " {\n"
-     << "  CEFBS_None,\n";
+  OS << "static FeatureBitset computeRequiredFeatures(unsigned Opcode) {\n"
+     << "  enum : " << getMinimalTypeForRange(FeatureBitsets.size()) << " {\n"
+     << "    CEFBS_None,\n";
   for (const auto &FeatureBitset : FeatureBitsets) {
     if (FeatureBitset.empty())
       continue;
-    OS << "  " << getNameForFeatureBitset(FeatureBitset) << ",\n";
+    OS << "    " << getNameForFeatureBitset(FeatureBitset) << ",\n";
   }
-  OS << "};\n\n"
-     << "static constexpr FeatureBitset FeatureBitsets[] = {\n"
-     << "  {}, // CEFBS_None\n";
+  OS << "  };\n\n"
+     << "  static constexpr FeatureBitset FeatureBitsets[] = {\n"
+     << "    {}, // CEFBS_None\n";
   for (const auto &FeatureBitset : FeatureBitsets) {
     if (FeatureBitset.empty())
       continue;
-    OS << "  {";
+    OS << "    {";
     for (const auto &Feature : FeatureBitset) {
       const auto &I = SubtargetFeatures.find(Feature);
       assert(I != SubtargetFeatures.end() && "Didn't import predicate?");
       OS << I->second.getEnumBitName() << ", ";
     }
     OS << "},\n";
   }
-  OS << "};\n"
-     << "#endif // NDEBUG\n\n";
-
-  // Emit the predicate verifier.
-  OS << "void verifyInstructionPredicates(\n"
-     << "    unsigned Opcode, const FeatureBitset &Features) {\n"
-     << "#ifndef NDEBUG\n"
+  OS << "  };\n"
      << "  static " << getMinimalTypeForRange(FeatureBitsets.size())
      << " RequiredFeaturesRefs[] = {\n";
   unsigned InstIdx = 0;
   for (const CodeGenInstruction *Inst : Target.getInstructionsByEnumValue()) {
     OS << "    CEFBS";
     unsigned NumPredicates = 0;
     for (Record *Predicate : Inst->TheDef->getValueAsListOfDefs("Predicates")) {
       const auto &I = SubtargetFeatures.find(Predicate);
       if (I != SubtargetFeatures.end()) {
         OS << '_' << I->second.TheDef->getName();
         NumPredicates++;
       }
     }
     if (!NumPredicates)
       OS << "_None";
     OS << ", // " << Inst->TheDef->getName() << " = " << InstIdx << "\n";
     InstIdx++;
   }
-  OS << "  };\n\n";
-  OS << "  assert(Opcode < " << InstIdx << ");\n";
+  OS << "  };\n\n"
+     << "  assert(Opcode < " << InstIdx << ");\n"
+     << "  return FeatureBitsets[RequiredFeaturesRefs[Opcode]];\n"
+     << "}\n\n";
+
+  OS << "} // end namespace " << Target.getName() << "_MC\n"
+     << "} // end namespace llvm\n"
+     << "#endif // GET_COMPUTE_FEATURES\n\n";
+
+  OS << "#ifdef ENABLE_INSTR_PREDICATE_VERIFIER\n"
+     << "#undef ENABLE_INSTR_PREDICATE_VERIFIER\n"
+     << "#include <sstream>\n\n";
+
+  OS << "namespace llvm {\n";
+  OS << "namespace " << Target.getName() << "_MC {\n\n";
+
+  // Emit the name table for error messages.
+  OS << "#ifndef NDEBUG\n";
+  SubtargetFeatureInfo::emitNameTable(SubtargetFeatures, OS);
+  OS << "#endif // NDEBUG\n\n";
+
+  // Emit the predicate verifier.
+  OS << "void verifyInstructionPredicates(\n"
+     << "    unsigned Opcode, const FeatureBitset &Features) {\n"
+     << "#ifndef NDEBUG\n";
   OS << "  FeatureBitset AvailableFeatures = "
         "computeAvailableFeatures(Features);\n";
-  OS << "  const FeatureBitset &RequiredFeatures = "
-        "FeatureBitsets[RequiredFeaturesRefs[Opcode]];\n";
+  OS << "  FeatureBitset RequiredFeatures = "
+     << "computeRequiredFeatures(Opcode);\n";
   OS << "  FeatureBitset MissingFeatures =\n"
      << "      (AvailableFeatures & RequiredFeatures) ^\n"
      << "      RequiredFeatures;\n"
      << "  if (MissingFeatures.any()) {\n"
      << "    std::ostringstream Msg;\n"
      << "    Msg << \"Attempting to emit \" << &" << Target.getName()
      << "InstrNameData[" << Target.getName() << "InstrNameIndices[Opcode]]\n"
      << "        << \" instruction but the \";\n"