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

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.

Reviewers: qcolombet

Subscribers: qcolombet, beanz, mgorny, llvm-commits, modocache

Differential Revision: https://reviews.llvm.org/D25614

llvm-svn: 286945

1 files changed, 57 insertions, 0 deletions

diff --git a/llvm/utils/TableGen/SubtargetFeatureInfo.h b/llvm/utils/TableGen/SubtargetFeatureInfo.h
new file mode 100644
index 00000000000..ddd04d5bb45
--- /dev/null
+++ b/llvm/utils/TableGen/SubtargetFeatureInfo.h
@@ -0,0 +1,57 @@
+//===- 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