[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286945 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 89 insertions, 0 deletions

diff --git a/utils/TableGen/SubtargetFeatureInfo.cpp b/utils/TableGen/SubtargetFeatureInfo.cpp
new file mode 100644
index 00000000000..2f9e881ef3a
--- /dev/null
+++ b/utils/TableGen/SubtargetFeatureInfo.cpp
@@ -0,0 +1,89 @@
+//===- 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";
+}