[tablegen] Extract portions of AsmMatcherEmitter for re-use by another generator. NFC.

[dsanders]

Summary

This change is preparation for a change that will allow targets to verify that the instructions
they emit meet the predicates they specify. This is useful to ensure that C++
legalization/lowering/instruction-selection doesn't incorrectly select code for a different
subtarget than intended. Such cases are not caught by the integrated assembler when emitting
instructions directly to an object file.

[dsanders]

ping

[dsanders]

ping

This is a pre-requisite of D25618 which has been LGTM'd

[qcolombet]

Hi Daniel,

LGTM. Couple of nitpicks below.

Cheers,
-Quentin

utils/TableGen/AsmMatcherEmitter.cpp

1417–1423

I would rather stick to the explicit type here.

utils/TableGen/SubtargetFeatureInfo.cpp

31

Just a thought, shouldn't this string be an argument?
Indeed, if we really want to reuse the functionality we shouldn't bake assembler specific stuff in.

I'm fine with a comment saying that if we want to extend the reusability we would need to pass an additional parameter.

utils/TableGen/SubtargetFeatureInfo.h

43

Add comments on what TargetName and ClassName are used.
Also, don't copy the string -> StringRef or const &

[dsanders]

• explicit type
• std::string->StringRef
• Comment on parameters and AssemblerMatcherPredicate string

[dsanders]

Be slightly clearer in a comment

[dsanders]

utils/TableGen/SubtargetFeatureInfo.cpp

31

I agree that the name 'AssemblerMatcherPredicate' doesn't make as much sense as it used to but not because of the 'Assembler' part. The new use is still part of an assembler, it just receives the IR directly instead of parsing it from text. The bit that I think may be dubious is the 'Matcher' part because no matching occurs in the new use. At this point, I think it's really a 'MCPredicate' but I'm not convinced it's worth renaming just yet.

I'll add the comment in case someone adds other kinds of predicates in the future.

utils/TableGen/AsmMatcherEmitter.cpp

 //      to the regular operand parsing.
 //
 //   3. For a match success, each operand class that has a 'ParserMethod'
 //      becomes part of a switch from where the custom method is called.
 //
 //===----------------------------------------------------------------------===//
 
 #include "CodeGenTarget.h"
+#include "SubtargetFeatureInfo.h"
 #include "llvm/ADT/CachedHashString.h"
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"

 #define DEBUG_TYPE "asm-matcher-emitter"
 
 static cl::opt<std::string>
 MatchPrefix("match-prefix", cl::init(""),
             cl::desc("Only match instructions with the given prefix"));
 
 namespace {
 class AsmMatcherInfo;
-struct SubtargetFeatureInfo;
 
 // Register sets are used as keys in some second-order sets TableGen creates
 // when generating its data structures. This means that the order of two
 // RegisterSets can be seen in the outputted AsmMatcher tables occasionally, and
 // can even affect compiler output (at least seen in diagnostics produced when
 // all matches fail). So we use a type that sorts them consistently.
 typedef std::set<Record*, LessRecordByID> RegisterSet;
 
struct MatchableInfo {
   void dump() const;
 
 private:
   void tokenizeAsmString(AsmMatcherInfo const &Info,
                          AsmVariantInfo const &Variant);
   void addAsmOperand(StringRef Token, bool IsIsolatedToken = false);
 };
 
-/// SubtargetFeatureInfo - Helper class for storing information on a subtarget
-/// feature which participates in instruction matching.
-struct SubtargetFeatureInfo {
-  /// \brief The predicate record for this feature.
-  Record *TheDef;
-
-  /// \brief An unique index assigned to represent this feature.
-  uint64_t Index;
-
-  SubtargetFeatureInfo(Record *D, uint64_t Idx) : TheDef(D), Index(Idx) {}
-
-  /// \brief The name of the enumerated constant identifying this feature.
-  std::string getEnumName() const {
-    return "Feature_" + TheDef->getName();
-  }
-
-  void dump() const {
-    errs() << getEnumName() << " " << Index << "\n";
-    TheDef->dump();
-  }
-};
-
 struct OperandMatchEntry {
   unsigned OperandMask;
   const MatchableInfo* MI;
   ClassInfo *CI;
 
   static OperandMatchEntry create(const MatchableInfo *mi, ClassInfo *ci,
                                   unsigned opMask) {
     OperandMatchEntry X;
private:
   void buildAliasOperandReference(MatchableInfo *II, StringRef OpName,
                                   MatchableInfo::AsmOperand &Op);
 
 public:
   AsmMatcherInfo(Record *AsmParser,
                  CodeGenTarget &Target,
                  RecordKeeper &Records);
 
-  /// buildInfo - Construct the various tables used during matching.
+  /// Construct the various tables used during matching.
   void buildInfo();
 
   /// buildOperandMatchInfo - Build the necessary information to handle user
   /// defined operand parsing methods.
   void buildOperandMatchInfo();
 
   /// getSubtargetFeature - Lookup or create the subtarget feature info for the
   /// given operand.
for (const auto &OCM : OpClassMask) {
       OperandMatchInfo.push_back(OperandMatchEntry::create(MI.get(), CI,
                                                            OpMask));
     }
   }
 }
 
 void AsmMatcherInfo::buildInfo() {
   // Build information about all of the AssemblerPredicates.
-  std::vector<Record*> AllPredicates =
-    Records.getAllDerivedDefinitions("Predicate");
-  for (Record *Pred : AllPredicates) {
-    // Ignore predicates that are not intended for the assembler.
-    if (!Pred->getValueAsBit("AssemblerMatcherPredicate"))
-      continue;
-
-    if (Pred->getName().empty())
-      PrintFatalError(Pred->getLoc(), "Predicate has no name!");
-
-    SubtargetFeatures.insert(std::make_pair(
-        Pred, SubtargetFeatureInfo(Pred, SubtargetFeatures.size())));
-    DEBUG(SubtargetFeatures.find(Pred)->second.dump());
-    assert(SubtargetFeatures.size() <= 64 && "Too many subtarget features!");
-  }
+  const std::vector<std::pair<Record *, SubtargetFeatureInfo>>
+      &SubtargetFeaturePairs = SubtargetFeatureInfo::getAll(Records);
+  SubtargetFeatures.insert(SubtargetFeaturePairs.begin(),
+                           SubtargetFeaturePairs.end());
+  for (const auto &Pair : SubtargetFeatures)
+    DEBUG(Pair.second.dump());
 
   bool HasMnemonicFirst = AsmParser->getValueAsBit("HasMnemonicFirst");
 
   // Parse the instructions; we need to do this first so that we can gather the
   // singleton register classes.
   SmallPtrSet<Record*, 16> SingletonRegisters;
   unsigned VariantCount = Target.getAsmParserVariantCount();
   for (unsigned VC = 0; VC != VariantCount; ++VC) {
if (!Info.SubtargetFeatures.empty()) {
     OS << "  }\n";
   } else {
     // Nothing to emit, so skip the switch
     OS << "  return \"(unknown)\";\n";
   }
   OS << "}\n\n";
 }
 
-/// emitComputeAvailableFeatures - Emit the function to compute the list of
-/// available features given a subtarget.
-static void emitComputeAvailableFeatures(AsmMatcherInfo &Info,
-                                         raw_ostream &OS) {
-  std::string ClassName =
-    Info.AsmParser->getValueAsString("AsmParserClassName");
-
-  OS << "uint64_t " << Info.Target.getName() << ClassName << "::\n"
-     << "ComputeAvailableFeatures(const FeatureBitset& FB) const {\n";
-  OS << "  uint64_t Features = 0;\n";
-  for (const auto &SF : Info.SubtargetFeatures) {
-    const SubtargetFeatureInfo &SFI = SF.second;
-
-    OS << "  if (";
-    std::string CondStorage =
-      SFI.TheDef->getValueAsString("AssemblerCondString");
-    StringRef Conds = CondStorage;
-    std::pair<StringRef,StringRef> Comma = Conds.split(',');
-    bool First = true;
-    do {
-      if (!First)
-        OS << " && ";
-
-      bool Neg = false;
-      StringRef Cond = Comma.first;
-      if (Cond[0] == '!') {
-        Neg = true;
-        Cond = Cond.substr(1);
-      }
-
-      OS << "(";
-      if (Neg)
-        OS << "!";
-      OS << "FB[" << Info.Target.getName() << "::" << Cond << "])";
-
-      if (Comma.second.empty())
-        break;
-
-      First = false;
-      Comma = Comma.second.split(',');
-    } while (true);
-
-    OS << ")\n";
-    OS << "    Features |= " << SFI.getEnumName() << ";\n";
-  }
-  OS << "  return Features;\n";
-  OS << "}\n\n";
-}
-
 static std::string GetAliasRequiredFeatures(Record *R,
                                             const AsmMatcherInfo &Info) {
   std::vector<Record*> ReqFeatures = R->getValueAsListOfDefs("Predicates");
   std::string Result;
   unsigned NumFeatures = 0;
   for (unsigned i = 0, e = ReqFeatures.size(); i != e; ++i) {
     const SubtargetFeatureInfo *F = Info.getSubtargetFeature(ReqFeatures[i]);
 
#endif // NDEBUG
 
   // Emit the subclass predicate routine.
   emitIsSubclass(Target, Info.Classes, OS);
 
   // Emit the routine to validate an operand against a match class.
   emitValidateOperandClass(Info, OS);
 
   // Emit the available features compute function.
-  emitComputeAvailableFeatures(Info, OS);
+  SubtargetFeatureInfo::emitComputeAvailableFeatures(
+      Info.Target.getName(), ClassName, Info.SubtargetFeatures, OS);
 
   StringToOffsetTable StringTable;
 
   size_t MaxNumOperands = 0;
   unsigned MaxMnemonicIndex = 0;
   bool HasDeprecation = false;
   for (const auto &MI : Info.Matchables) {
     MaxNumOperands = std::max(MaxNumOperands, MI->AsmOperands.size());

utils/TableGen/CMakeLists.txt

add_tablegen(llvm-tblgen LLVM
   FixedLenDecoderEmitter.cpp
   InstrInfoEmitter.cpp
   IntrinsicEmitter.cpp
   OptParserEmitter.cpp
   PseudoLoweringEmitter.cpp
   RegisterInfoEmitter.cpp
   SearchableTableEmitter.cpp
   SubtargetEmitter.cpp
+  SubtargetFeatureInfo.cpp
   TableGen.cpp
   X86DisassemblerTables.cpp
   X86ModRMFilters.cpp
   X86RecognizableInstr.cpp
   CTagsEmitter.cpp
   )

utils/TableGen/SubtargetFeatureInfo.h

+//===- SubtargetFeatureInfo.h - Helpers for subtarget features ------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_UTIL_TABLEGEN_SUBTARGETFEATUREINFO_H
+#define LLVM_UTIL_TABLEGEN_SUBTARGETFEATUREINFO_H
+
+#include "llvm/TableGen/Error.h"
+#include "llvm/TableGen/Record.h"
+
+#include <map>
+
+namespace llvm {
+class Record;
+class RecordKeeper;
+
+/// Helper class for storing information on a subtarget feature which
+/// participates in instruction matching.
+struct SubtargetFeatureInfo {
+  /// \brief The predicate record for this feature.
+  Record *TheDef;
+
+  /// \brief An unique index assigned to represent this feature.
+  uint64_t Index;
+
+  SubtargetFeatureInfo(Record *D, uint64_t Idx) : TheDef(D), Index(Idx) {}
+
+  /// \brief The name of the enumerated constant identifying this feature.
+  std::string getEnumName() const { return "Feature_" + TheDef->getName(); }
+
+  void dump() const;
+  static std::vector<std::pair<Record *, SubtargetFeatureInfo>>
+  getAll(const RecordKeeper &Records);
+
+  /// Emit the function to compute the list of available features given a
+  /// subtarget.
+  ///
+  /// \param TargetName The name of the target as used in class prefixes (e.g.
+  ///                   <TargetName>Subtarget)
+  /// \param ClassName  The name of the class (without the <Target> prefix)
+  ///                   that will contain the generated functions.
+  /// \param SubtargetFeatures A map of TableGen records to the
+  ///                          SubtargetFeatureInfo equivalent.
+  static void emitComputeAvailableFeatures(
+      StringRef TargetName, StringRef ClassName,
+      std::map<Record *, SubtargetFeatureInfo, LessRecordByID>
+          &SubtargetFeatures,
+      raw_ostream &OS);
+};
+} // end namespace llvm
+
+#endif // LLVM_UTIL_TABLEGEN_SUBTARGETFEATUREINFO_H

utils/TableGen/SubtargetFeatureInfo.cpp

+//===- SubtargetFeatureInfo.cpp - Helpers for subtarget features ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "SubtargetFeatureInfo.h"
+
+#include "llvm/TableGen/Record.h"
+
+#include <map>
+
+using namespace llvm;
+
+void SubtargetFeatureInfo::dump() const {
+  errs() << getEnumName() << " " << Index << "\n";
+  TheDef->dump();
+}
+
+std::vector<std::pair<Record *, SubtargetFeatureInfo>>
+SubtargetFeatureInfo::getAll(const RecordKeeper &Records) {
+  std::vector<std::pair<Record *, SubtargetFeatureInfo>> SubtargetFeatures;
+  std::vector<Record *> AllPredicates =
+      Records.getAllDerivedDefinitions("Predicate");
+  for (Record *Pred : AllPredicates) {
+    // Ignore predicates that are not intended for the assembler.
+    //
+    // The "AssemblerMatcherPredicate" string should be promoted to an argument
+    // if we re-use the machinery for non-assembler purposes in future.
+    if (!Pred->getValueAsBit("AssemblerMatcherPredicate"))
+      continue;
+
+    if (Pred->getName().empty())
+      PrintFatalError(Pred->getLoc(), "Predicate has no name!");
+
+    SubtargetFeatures.emplace_back(
+        Pred, SubtargetFeatureInfo(Pred, SubtargetFeatures.size()));
+  }
+  return SubtargetFeatures;
+}
+
+void SubtargetFeatureInfo::emitComputeAvailableFeatures(
+    StringRef TargetName, StringRef ClassName,
+    std::map<Record *, SubtargetFeatureInfo, LessRecordByID> &SubtargetFeatures,
+    raw_ostream &OS) {
+  OS << "uint64_t " << TargetName << ClassName << "::\n"
+     << "ComputeAvailableFeatures(const FeatureBitset& FB) const {\n";
+  OS << "  uint64_t Features = 0;\n";
+  for (const auto &SF : SubtargetFeatures) {
+    const SubtargetFeatureInfo &SFI = SF.second;
+
+    OS << "  if (";
+    std::string CondStorage =
+        SFI.TheDef->getValueAsString("AssemblerCondString");
+    StringRef Conds = CondStorage;
+    std::pair<StringRef, StringRef> Comma = Conds.split(',');
+    bool First = true;
+    do {
+      if (!First)
+        OS << " && ";
+
+      bool Neg = false;
+      StringRef Cond = Comma.first;
+      if (Cond[0] == '!') {
+        Neg = true;
+        Cond = Cond.substr(1);
+      }
+
+      OS << "(";
+      if (Neg)
+        OS << "!";
+      OS << "FB[" << TargetName << "::" << Cond << "])";
+
+      if (Comma.second.empty())
+        break;
+
+      First = false;
+      Comma = Comma.second.split(',');
+    } while (true);
+
+    OS << ")\n";
+    OS << "    Features |= " << SFI.getEnumName() << ";\n";
+  }
+  OS << "  return Features;\n";
+  OS << "}\n\n";
+}