Re-commit: [globalisel] Tablegen-erate current Register Bank Information

Summary:
Adds a RegisterBank tablegen class that can be used to declare the register
banks and an associated tablegen pass to generate the necessary code.

Changes since last commit:
The new tablegen pass is now correctly guarded by LLVM_BUILD_GLOBAL_ISEL and
this should fix the buildbots however it may not be the whole fix. The previous
buildbot failures suggest there may be a memory bug lurking that I'm unable to
reproduce (including when using asan) or spot in the source. If they re-occur
on this commit then I'll need assistance from the bot owners to track it down.

Reviewers: t.p.northover, ab, rovka, qcolombet

Reviewed By: qcolombet

Subscribers: aditya_nandakumar, rengolin, kristof.beyls, vkalintiris, mgorny, dberris, llvm-commits, rovka

Differential Revision: https://reviews.llvm.org/D27338



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292367 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 309 insertions, 0 deletions

diff --git a/utils/TableGen/RegisterBankEmitter.cpp b/utils/TableGen/RegisterBankEmitter.cpp
new file mode 100644
index 00000000000..a33c9a87cac
--- /dev/null
+++ b/utils/TableGen/RegisterBankEmitter.cpp
@@ -0,0 +1,309 @@
+//===- RegisterBankEmitter.cpp - Generate a Register Bank Desc. -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This tablegen backend is responsible for emitting a description of a target
+// register bank for a code generator.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/BitVector.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/TableGen/Error.h"
+#include "llvm/TableGen/Record.h"
+#include "llvm/TableGen/TableGenBackend.h"
+
+#include "CodeGenRegisters.h"
+
+#define DEBUG_TYPE "register-bank-emitter"
+
+using namespace llvm;
+
+namespace {
+class RegisterBank {
+
+  /// A vector of register classes that are included in the register bank.
+  typedef std::vector<const CodeGenRegisterClass *> RegisterClassesTy;
+
+private:
+  const Record &TheDef;
+
+  /// The register classes that are covered by the register bank.
+  RegisterClassesTy RCs;
+
+  /// The register class with the largest register size.
+  const CodeGenRegisterClass *RCWithLargestRegsSize;
+
+public:
+  RegisterBank(const Record &TheDef)
+      : TheDef(TheDef), RCs(), RCWithLargestRegsSize(nullptr) {}
+
+  /// Get the human-readable name for the bank.
+  std::string getName() const { return TheDef.getValueAsString("Name"); }
+  /// Get the name of the enumerator in the ID enumeration.
+  std::string getEnumeratorName() const { return (TheDef.getName() + "ID").str(); }
+
+  /// Get the name of the array holding the register class coverage data;
+  std::string getCoverageArrayName() const {
+    return (TheDef.getName() + "CoverageData").str();
+  }
+
+  /// Get the name of the global instance variable.
+  StringRef getInstanceVarName() const { return TheDef.getName(); }
+
+  const Record &getDef() const { return TheDef; }
+
+  /// Get the register classes listed in the RegisterBank.RegisterClasses field.
+  std::vector<const CodeGenRegisterClass *>
+  getExplictlySpecifiedRegisterClasses(
+      CodeGenRegBank &RegisterClassHierarchy) const {
+    std::vector<const CodeGenRegisterClass *> RCs;
+    for (const auto &RCDef : getDef().getValueAsListOfDefs("RegisterClasses"))
+      RCs.push_back(RegisterClassHierarchy.getRegClass(RCDef));
+    return RCs;
+  }
+
+  /// Add a register class to the bank without duplicates.
+  void addRegisterClass(const CodeGenRegisterClass *RC) {
+    if (std::find_if(RCs.begin(), RCs.end(),
+                     [&RC](const CodeGenRegisterClass *X) {
+                       return X == RC;
+                     }) != RCs.end())
+      return;
+
+    // FIXME? We really want the register size rather than the spill size
+    //        since the spill size may be bigger on some targets with
+    //        limited load/store instructions. However, we don't store the
+    //        register size anywhere (we could sum the sizes of the subregisters
+    //        but there may be additional bits too) and we can't derive it from
+    //        the VT's reliably due to Untyped.
+    if (RCWithLargestRegsSize == nullptr)
+      RCWithLargestRegsSize = RC;
+    else if (RCWithLargestRegsSize->SpillSize < RC->SpillSize)
+      RCWithLargestRegsSize = RC;
+    assert(RCWithLargestRegsSize && "RC was nullptr?");
+
+    RCs.emplace_back(RC);
+  }
+
+  const CodeGenRegisterClass *getRCWithLargestRegsSize() const {
+    return RCWithLargestRegsSize;
+  }
+
+  iterator_range<typename RegisterClassesTy::const_iterator>
+  register_classes() const {
+    return llvm::make_range(RCs.begin(), RCs.end());
+  }
+};
+
+class RegisterBankEmitter {
+private:
+  RecordKeeper &Records;
+  CodeGenRegBank RegisterClassHierarchy;
+
+  void emitHeader(raw_ostream &OS, const StringRef TargetName,
+                  const std::vector<RegisterBank> &Banks);
+  void emitBaseClassDefinition(raw_ostream &OS, const StringRef TargetName,
+                               const std::vector<RegisterBank> &Banks);
+  void emitBaseClassImplementation(raw_ostream &OS, const StringRef TargetName,
+                                   std::vector<RegisterBank> &Banks);
+
+public:
+  RegisterBankEmitter(RecordKeeper &R)
+      : Records(R), RegisterClassHierarchy(Records) {}
+
+  void run(raw_ostream &OS);
+};
+
+} // end anonymous namespace
+
+/// Emit code to declare the ID enumeration and external global instance
+/// variables.
+void RegisterBankEmitter::emitHeader(raw_ostream &OS,
+                                     const StringRef TargetName,
+                                     const std::vector<RegisterBank> &Banks) {
+  // <Target>RegisterBankInfo.h
+  OS << "namespace llvm {\n"
+     << "namespace " << TargetName << " {\n"
+     << "enum {\n";
+  for (const auto &Bank : Banks)
+    OS << "  " << Bank.getEnumeratorName() << ",\n";
+  OS << "  NumRegisterBanks,\n"
+     << "};\n"
+     << "} // end namespace " << TargetName << "\n"
+     << "} // end namespace llvm\n";
+}
+
+/// Emit declarations of the <Target>GenRegisterBankInfo class.
+void RegisterBankEmitter::emitBaseClassDefinition(
+    raw_ostream &OS, const StringRef TargetName,
+    const std::vector<RegisterBank> &Banks) {
+  OS << "private:\n"
+     << "  static RegisterBank *RegBanks[];\n\n"
+     << "protected:\n"
+     << "  " << TargetName << "GenRegisterBankInfo();\n"
+     << "\n";
+}
+
+/// Visit each register class belonging to the given register bank.
+///
+/// A class belongs to the bank iff any of these apply:
+/// * It is explicitly specified
+/// * It is a subclass of a class that is a member.
+/// * It is a class containing subregisters of the registers of a class that
+///   is a member. This is known as a subreg-class.
+///
+/// This function must be called for each explicitly specified register class.
+///
+/// \param RC The register class to search.
+/// \param Kind A debug string containing the path the visitor took to reach RC.
+/// \param VisitFn The action to take for each class visited. It may be called
+///                multiple times for a given class if there are multiple paths
+///                to the class.
+static void visitRegisterBankClasses(
+    CodeGenRegBank &RegisterClassHierarchy, const CodeGenRegisterClass *RC,
+    const Twine Kind,
+    std::function<void(const CodeGenRegisterClass *, StringRef)> VisitFn) {
+  // Visit each explicitly named class.
+  VisitFn(RC, Kind.str());
+
+  for (const auto &PossibleSubclass : RegisterClassHierarchy.getRegClasses()) {
+    Twine TmpKind = Kind + " (" + PossibleSubclass.getName() + ")";
+
+    // Visit each subclass of an explicitly named class.
+    if (RC != &PossibleSubclass && RC->hasSubClass(&PossibleSubclass))
+      visitRegisterBankClasses(RegisterClassHierarchy, &PossibleSubclass,
+                               TmpKind + " " + RC->getName() + " subclass",
+                               VisitFn);
+
+    // Visit each class that contains only subregisters of RC with a common
+    // subregister-index.
+    //
+    // More precisely, PossibleSubclass is a subreg-class iff Reg:SubIdx is in
+    // PossibleSubclass for all registers Reg from RC using any
+    // subregister-index SubReg
+    for (const auto &SubIdx : RegisterClassHierarchy.getSubRegIndices()) {
+      BitVector BV(RegisterClassHierarchy.getRegClasses().size());
+      PossibleSubclass.getSuperRegClasses(&SubIdx, BV);
+      if (BV.test(RC->EnumValue)) {
+        Twine TmpKind2 = TmpKind + " " + RC->getName() +
+                         " class-with-subregs: " + RC->getName();
+        VisitFn(&PossibleSubclass, TmpKind2.str());
+      }
+    }
+  }
+}
+
+void RegisterBankEmitter::emitBaseClassImplementation(
+    raw_ostream &OS, StringRef TargetName,
+    std::vector<RegisterBank> &Banks) {
+
+  OS << "namespace llvm {\n"
+     << "namespace " << TargetName << " {\n";
+  for (const auto &Bank : Banks) {
+    std::vector<std::vector<const CodeGenRegisterClass *>> RCsGroupedByWord(
+        (RegisterClassHierarchy.getRegClasses().size() + 31) / 32);
+
+    for (const auto &RC : Bank.register_classes())
+      RCsGroupedByWord[RC->EnumValue / 32].push_back(RC);
+
+    OS << "const uint32_t " << Bank.getCoverageArrayName() << "[] = {\n";
+    unsigned LowestIdxInWord = 0;
+    for (const auto &RCs : RCsGroupedByWord) {
+      OS << "    // " << LowestIdxInWord << "-" << (LowestIdxInWord + 31) << "\n";
+      for (const auto &RC : RCs) {
+        Twine QualifiedRegClassID =
+            TargetName + "::" + RC->getName() + "RegClassID";
+        OS << "    (1u << (" << QualifiedRegClassID << " - "
+           << LowestIdxInWord << ")) |\n";
+      }
+      OS << "    0,\n";
+      LowestIdxInWord += 32;
+    }
+    OS << "};\n";
+  }
+  OS << "\n";
+
+  for (const auto &Bank : Banks) {
+    Twine QualifiedBankID = TargetName + "::" + Bank.getEnumeratorName();
+    unsigned Size = Bank.getRCWithLargestRegsSize()->SpillSize;
+    OS << "RegisterBank " << Bank.getInstanceVarName() << "(/* ID */ "
+       << QualifiedBankID << ", /* Name */ \"" << Bank.getName()
+       << "\", /* Size */ " << Size << ", "
+       << "/* CoveredRegClasses */ " << Bank.getCoverageArrayName()
+       << ", /* NumRegClasses */ "
+       << RegisterClassHierarchy.getRegClasses().size() << ");\n";
+  }
+  OS << "} // end namespace " << TargetName << "\n"
+     << "\n";
+
+  OS << "RegisterBank *" << TargetName
+     << "GenRegisterBankInfo::RegBanks[] = {\n";
+  for (const auto &Bank : Banks)
+    OS << "    &" << TargetName << "::" << Bank.getInstanceVarName() << ",\n";
+  OS << "};\n\n";
+
+  OS << TargetName << "GenRegisterBankInfo::" << TargetName
+     << "GenRegisterBankInfo()\n"
+     << "    : RegisterBankInfo(RegBanks, " << TargetName
+     << "::NumRegisterBanks) {\n"
+     << "  // Assert that RegBank indices match their ID's\n"
+     << "  unsigned Index = 0;\n"
+     << "#ifndef NDEBUG\n"
+     << "  for (const auto &RB : RegBanks)\n"
+     << "    assert(Index++ == RB->getID() && \"Index != ID\");\n"
+     << "#endif // NDEBUG\n"
+     << "}\n"
+     << "} // end namespace llvm\n";
+}
+
+void RegisterBankEmitter::run(raw_ostream &OS) {
+  std::vector<Record*> Targets = Records.getAllDerivedDefinitions("Target");
+  if (Targets.size() != 1)
+    PrintFatalError("ERROR: Too many or too few subclasses of Target defined!");
+  StringRef TargetName = Targets[0]->getName();
+
+  std::vector<RegisterBank> Banks;
+  for (const auto &V : Records.getAllDerivedDefinitions("RegisterBank")) {
+    RegisterBank Bank(*V);
+
+    for (const CodeGenRegisterClass *RC :
+         Bank.getExplictlySpecifiedRegisterClasses(RegisterClassHierarchy)) {
+      visitRegisterBankClasses(
+          RegisterClassHierarchy, RC, "explicit",
+          [&Bank](const CodeGenRegisterClass *RC, StringRef Kind) {
+            DEBUG(dbgs() << "Added " << RC->getName() << "(" << Kind << ")\n");
+            Bank.addRegisterClass(RC);
+          });
+    }
+
+    Banks.push_back(Bank);
+  }
+
+  emitSourceFileHeader("Register Bank Source Fragments", OS);
+  OS << "#ifdef GET_REGBANK_DECLARATIONS\n"
+     << "#undef GET_REGBANK_DECLARATIONS\n";
+  emitHeader(OS, TargetName, Banks);
+  OS << "#endif // GET_REGBANK_DECLARATIONS\n\n"
+     << "#ifdef GET_TARGET_REGBANK_CLASS\n"
+     << "#undef GET_TARGET_REGBANK_CLASS\n";
+  emitBaseClassDefinition(OS, TargetName, Banks);
+  OS << "#endif // GET_TARGET_REGBANK_CLASS\n\n"
+     << "#ifdef GET_TARGET_REGBANK_IMPL\n"
+     << "#undef GET_TARGET_REGBANK_IMPL\n";
+  emitBaseClassImplementation(OS, TargetName, Banks);
+  OS << "#endif // GET_TARGET_REGBANK_IMPL\n";
+}
+
+namespace llvm {
+
+void EmitRegisterBank(RecordKeeper &RK, raw_ostream &OS) {
+  RegisterBankEmitter(RK).run(OS);
+}
+
+} // end namespace llvm