[RISCV]Add support for resolving encoding conflicts among vendor specific CSRs

Garvit Gupta · Garvit Gupta · commit 26421c45cceb · 2024-07-01T05:49:14.000-07:00
This patch adds the framework for resolving encoding conflicts among CSRs.

Specifically, this patch adds a support for emitting a new lookup function for
the primary key which return a pair of iterators pointing to first and last
value hence giving a range of values which satisfies the query.

While printing the CSR name during objdump, iterate over the range and print the
name of only that CSR which satisifes the feature requirement of subtarget.

Below is the signature of the new function that will be emitted for primary key:

```
llvm::iterator_range&lt;const SysReg *&gt;lookupSysRegByEncoding(uint16_t Encoding) {
  SysReg Key;
  Key.Encoding = Encoding;
  auto Table = ArrayRef(SysRegsList);
  auto It = std::equal_range(Table.begin(), Table.end(), Key,
    [](const SysReg &amp;LHS, const SysReg &amp;RHS) {
      if (LHS.Encoding &lt; RHS.Encoding)
        return true;
      if (LHS.Encoding &gt; RHS.Encoding)
        return false;
      return false;
    });

  return llvm::make_range(It.first, It.second);
}
```
diff --git a/llvm/include/llvm/TableGen/SearchableTable.td b/llvm/include/llvm/TableGen/SearchableTable.td
@@ -114,6 +114,9 @@ class GenericTable {
 
   // See SearchIndex.EarlyOut
   bit PrimaryKeyEarlyOut = false;
+
+  // See SearchIndex.ReturnRange
+  bit PrimaryKeyReturnRange = false;
 }
 
 // Define a record derived from this class to generate an additional search
@@ -135,6 +138,11 @@ class SearchIndex {
   //
   // Can only be used when the first field is an integral (non-string) type.
   bit EarlyOut = false;
+
+  // If true, will generate a different function signature which will return a
+  // iterator range of pointers giving the starting and end value of the range.
+  // e.g. lookupSysRegByEncoding returns multiple CSRs for same encoding.
+  bit ReturnRange = false;
 }
 
 // Legacy table type with integrated enum.
diff --git a/llvm/test/TableGen/EncodingConflict.td b/llvm/test/TableGen/EncodingConflict.td
@@ -0,0 +1,108 @@
+// RUN: llvm-tblgen -gen-searchable-tables -I %p/../../include %s | FileCheck %s
+
+include "llvm/TableGen/SearchableTable.td"
+
+class SysReg<string name, bits<12> op> {
+  string Name = name;
+  bits<12> Encoding = op;
+  code FeaturesRequired = [{ {} }];
+}
+
+def List1 : GenericTable {
+  let FilterClass = "SysReg";
+  let Fields = [
+     "Name", "Encoding", "FeaturesRequired",
+  ];
+
+  let PrimaryKey = [ "Encoding" ];
+  let PrimaryKeyName = "lookupSysRegByEncoding";
+  let PrimaryKeyReturnRange = true;
+}
+
+let FeaturesRequired = [{ {Feature1} }] in {
+def : SysReg<"csr1", 0x7C0>;
+}
+
+let FeaturesRequired = [{ {Feature2} }] in {
+def : SysReg<"csr2", 0x7C0>;
+}
+
+// CHECK: #ifdef GET_List1_DECL
+// CHECK-NEXT: llvm::iterator_range<const SysReg *>lookupSysRegByEncoding(uint16_t Encoding);
+// CHECK-NEXT: #endif
+
+// CHECK: #ifdef GET_List1_IMPL
+// CHECK-NEXT: constexpr SysReg List1[] = {
+// CHECK-NEXT:   { "csr1", 0x7C0,  {Feature1}  }, // 0
+// CHECK-NEXT:   { "csr2", 0x7C0,  {Feature2}  }, // 1
+// CHECK-NEXT:  };
+
+// CHECK: llvm::iterator_range<const SysReg *>lookupSysRegByEncoding(uint16_t Encoding) {
+// CHECK-NEXT:   SysReg Key;
+// CHECK-NEXT:   Key.Encoding = Encoding;
+// CHECK-NEXT:   auto Table = ArrayRef(List1);
+// CHECK-NEXT:   auto It = std::equal_range(Table.begin(), Table.end(), Key,
+// CHECK-NEXT:     [](const SysReg &LHS, const SysReg &RHS) {
+// CHECK-NEXT:       if (LHS.Encoding < RHS.Encoding)
+// CHECK-NEXT:         return true;
+// CHECK-NEXT:       if (LHS.Encoding > RHS.Encoding)
+// CHECK-NEXT:         return false;
+// CHECK-NEXT:       return false;
+// CHECK-NEXT:     });
+
+// CHECK:   return llvm::make_range(It.first, It.second);
+// CHECK-NEXT: }
+// CHECK-NEXT: #endif
+
+def List2 : GenericTable {
+  let FilterClass = "SysReg";
+  let Fields = [
+     "Name", "Encoding", "FeaturesRequired",
+  ];
+}
+
+def lookupSysRegByName : SearchIndex {
+  let Table = List2;
+  let Key = [ "Name" ];
+  let ReturnRange = true;
+}
+
+// CHECK: #ifdef GET_List2_DECL
+// CHECK-NEXT: llvm::iterator_range<const SysReg *>lookupSysRegByName(StringRef Name);
+// CHECK-NEXT: #endif
+
+// CHECK: #ifdef GET_List2_IMPL
+// CHECK-NEXT: constexpr SysReg List2[] = {
+// CHECK-NEXT:   { "csr1", 0x7C0,  {Feature1}  }, // 0
+// CHECK-NEXT:   { "csr2", 0x7C0,  {Feature2}  }, // 1
+// CHECK-NEXT:  };
+
+// CHECK: llvm::iterator_range<const SysReg *>lookupSysRegByName(StringRef Name) {
+// CHECK-NEXT:   struct IndexType {
+// CHECK-NEXT:     const char * Name;
+// CHECK-NEXT:     unsigned _index;
+// CHECK-NEXT:   };
+// CHECK-NEXT:   static const struct IndexType Index[] = {
+// CHECK-NEXT:     { "CSR1", 0 },
+// CHECK-NEXT:     { "CSR2", 1 },
+// CHECK-NEXT:   };
+
+// CHECK:   IndexType Key;
+// CHECK-NEXT:   Key.Name = Name.upper();
+// CHECK-NEXT:   auto Table = ArrayRef(Index);
+// CHECK-NEXT:   auto It = std::equal_range(Table.begin(), Table.end(), Key,
+// CHECK-NEXT:     [](const IndexType &LHS, const IndexType &RHS) {
+// CHECK-NEXT:       int CmpName = StringRef(LHS.Name).compare(RHS.Name);
+// CHECK-NEXT:       if (CmpName < 0) return true;
+// CHECK-NEXT:       if (CmpName > 0) return false;
+// CHECK-NEXT:       return false;
+// CHECK-NEXT:     });
+
+// CHECK:   return llvm::make_range(It.first, It.second);
+// CHECK-NEXT: }
+// CHECK-NEXT: #endif
+
+// CHECK: #undef GET_List1_DECL
+// CHECK-NEXT: #undef GET_List1_IMPL
+// CHECK-NEXT: #undef GET_List2_DECL
+// CHECK-NEXT: #undef GET_List2_IMPL
diff --git a/llvm/utils/TableGen/SearchableTableEmitter.cpp b/llvm/utils/TableGen/SearchableTableEmitter.cpp
@@ -68,6 +68,7 @@ struct SearchIndex {
   SMLoc Loc; // Source location of PrimaryKey or Key field definition.
   SmallVector<GenericField, 1> Fields;
   bool EarlyOut = false;
+  bool ReturnRange = false;
 };
 
 struct GenericTable {
@@ -198,7 +199,8 @@ class SearchableTableEmitter {
   bool parseFieldType(GenericField &Field, Init *II);
   std::unique_ptr<SearchIndex>
   parseSearchIndex(GenericTable &Table, const RecordVal *RecVal, StringRef Name,
-                   const std::vector<StringRef> &Key, bool EarlyOut);
+                   const std::vector<StringRef> &Key, bool EarlyOut,
+                   bool ReturnRange);
   void collectEnumEntries(GenericEnum &Enum, StringRef NameField,
                           StringRef ValueField,
                           const std::vector<Record *> &Items);
@@ -426,16 +428,25 @@ void SearchableTableEmitter::emitLookupFunction(const GenericTable &Table,
     OS << "    return nullptr;\n\n";
   }
 
-  OS << "  struct KeyType {\n";
-  for (const auto &Field : Index.Fields) {
-    OS << "    " << searchableFieldType(Table, Index, Field, TypeInTempStruct)
-       << " " << Field.Name << ";\n";
+  bool ShouldReturnRange = Index.ReturnRange;
+  if (ShouldReturnRange)
+    OS << "  " << IndexTypeName << " Key;\n";
+  else {
+    OS << "  struct KeyType {\n";
+    for (const auto &Field : Index.Fields) {
+      OS << "    " << searchableFieldType(Table, Index, Field, TypeInTempStruct)
+         << " " << Field.Name << ";\n";
+    }
+    OS << "  };\n";
+    OS << "  KeyType Key = {";
   }
-  OS << "  };\n";
-  OS << "  KeyType Key = {";
+
   ListSeparator LS;
   for (const auto &Field : Index.Fields) {
-    OS << LS << Field.Name;
+    if (ShouldReturnRange)
+      OS << "  Key." << Field.Name << " = " << Field.Name;
+    else
+      OS << LS << Field.Name;
     if (isa<StringRecTy>(Field.RecType)) {
       OS << ".upper()";
       if (IsPrimary)
@@ -445,12 +456,21 @@ void SearchableTableEmitter::emitLookupFunction(const GenericTable &Table,
                             "case-insensitive comparison of field '" +
                             Field.Name + "'");
     }
+    if (ShouldReturnRange)
+      OS << ";\n";
   }
-  OS << "};\n";
+  if (!ShouldReturnRange)
+    OS << "};\n";
 
   OS << "  auto Table = ArrayRef(" << IndexName << ");\n";
-  OS << "  auto Idx = std::lower_bound(Table.begin(), Table.end(), Key,\n";
-  OS << "    [](const " << IndexTypeName << " &LHS, const KeyType &RHS) {\n";
+  if (ShouldReturnRange) {
+    OS << "  auto It = std::equal_range(Table.begin(), Table.end(), Key,\n";
+    OS << "    [](const " << IndexTypeName << " &LHS, const " << IndexTypeName
+       << " &RHS) {\n";
+  } else {
+    OS << "  auto Idx = std::lower_bound(Table.begin(), Table.end(), Key,\n";
+    OS << "    [](const " << IndexTypeName << " &LHS, const KeyType &RHS) {\n";
+  }
 
   for (const auto &Field : Index.Fields) {
     if (isa<StringRecTy>(Field.RecType)) {
@@ -478,25 +498,33 @@ void SearchableTableEmitter::emitLookupFunction(const GenericTable &Table,
   OS << "      return false;\n";
   OS << "    });\n\n";
 
-  OS << "  if (Idx == Table.end()";
-
-  for (const auto &Field : Index.Fields)
-    OS << " ||\n      Key." << Field.Name << " != Idx->" << Field.Name;
-  OS << ")\n    return nullptr;\n";
+  if (!ShouldReturnRange) {
+    OS << "  if (Idx == Table.end()";
+    for (const auto &Field : Index.Fields)
+      OS << " ||\n      Key." << Field.Name << " != Idx->" << Field.Name;
+  }
 
-  if (IsPrimary)
+  if (ShouldReturnRange)
+    OS << "  return llvm::make_range(It.first, It.second);\n";
+  else if (IsPrimary) {
+    OS << ")\n    return nullptr;\n\n";
     OS << "  return &*Idx;\n";
-  else
+  } else {
+    OS << ")\n    return nullptr;\n\n";
     OS << "  return &" << Table.Name << "[Idx->_index];\n";
+  }
 
   OS << "}\n";
 }
 
 void SearchableTableEmitter::emitLookupDeclaration(const GenericTable &Table,
                                                    const SearchIndex &Index,
                                                    raw_ostream &OS) {
-  OS << "const " << Table.CppTypeName << " *" << Index.Name << "(";
-
+  if (Index.ReturnRange)
+    OS << "llvm::iterator_range<const " << Table.CppTypeName << " *> ";
+  else
+    OS << "const " << Table.CppTypeName << " *";
+  OS << Index.Name << "(";
   ListSeparator LS;
   for (const auto &Field : Index.Fields)
     OS << LS << searchableFieldType(Table, Index, Field, TypeInArgument) << " "
@@ -510,11 +538,12 @@ void SearchableTableEmitter::emitGenericTable(const GenericTable &Table,
 
   // Emit the declarations for the functions that will perform lookup.
   if (Table.PrimaryKey) {
-    emitLookupDeclaration(Table, *Table.PrimaryKey, OS);
+    auto &Index = Table.PrimaryKey;
+    emitLookupDeclaration(Table, *Index, OS);
     OS << ";\n";
   }
   for (const auto &Index : Table.Indices) {
-    emitLookupDeclaration(Table, *Index, OS);
+    emitLookupDeclaration(Table, *Index,  OS);
     OS << ";\n";
   }
 
@@ -540,10 +569,12 @@ void SearchableTableEmitter::emitGenericTable(const GenericTable &Table,
 
   // Indexes are sorted "{ Thing, PrimaryIdx }" arrays, so that a binary
   // search can be performed by "Thing".
-  if (Table.PrimaryKey)
-    emitLookupFunction(Table, *Table.PrimaryKey, true, OS);
+  if (Table.PrimaryKey) {
+    auto &Index = Table.PrimaryKey;
+    emitLookupFunction(Table, *Index, /*IsPrimary=*/true, OS);
+  }
   for (const auto &Index : Table.Indices)
-    emitLookupFunction(Table, *Index, false, OS);
+    emitLookupFunction(Table, *Index, /*IsPrimary=*/false, OS);
 
   OS << "#endif\n\n";
 }
@@ -569,11 +600,12 @@ bool SearchableTableEmitter::parseFieldType(GenericField &Field, Init *TypeOf) {
 
 std::unique_ptr<SearchIndex> SearchableTableEmitter::parseSearchIndex(
     GenericTable &Table, const RecordVal *KeyRecVal, StringRef Name,
-    const std::vector<StringRef> &Key, bool EarlyOut) {
+    const std::vector<StringRef> &Key, bool EarlyOut, bool ReturnRange) {
   auto Index = std::make_unique<SearchIndex>();
   Index->Name = std::string(Name);
   Index->Loc = KeyRecVal->getLoc();
   Index->EarlyOut = EarlyOut;
+  Index->ReturnRange = ReturnRange;
 
   for (const auto &FieldName : Key) {
     const GenericField *Field = Table.getFieldByName(FieldName);
@@ -769,7 +801,8 @@ void SearchableTableEmitter::run(raw_ostream &OS) {
           parseSearchIndex(*Table, TableRec->getValue("PrimaryKey"),
                            TableRec->getValueAsString("PrimaryKeyName"),
                            TableRec->getValueAsListOfStrings("PrimaryKey"),
-                           TableRec->getValueAsBit("PrimaryKeyEarlyOut"));
+                           TableRec->getValueAsBit("PrimaryKeyEarlyOut"),
+                           TableRec->getValueAsBit("PrimaryKeyReturnRange"));
 
       llvm::stable_sort(Table->Entries, [&](Record *LHS, Record *RHS) {
         return compareBy(LHS, RHS, *Table->PrimaryKey);
@@ -793,7 +826,8 @@ void SearchableTableEmitter::run(raw_ostream &OS) {
     Table.Indices.push_back(
         parseSearchIndex(Table, IndexRec->getValue("Key"), IndexRec->getName(),
                          IndexRec->getValueAsListOfStrings("Key"),
-                         IndexRec->getValueAsBit("EarlyOut")));
+                         IndexRec->getValueAsBit("EarlyOut"),
+                         IndexRec->getValueAsBit("ReturnRange")));
   }
 
   // Translate legacy tables.
@@ -848,7 +882,7 @@ void SearchableTableEmitter::run(raw_ostream &OS) {
       std::string Name =
           (Twine("lookup") + Table->CppTypeName + "By" + Field).str();
       Table->Indices.push_back(parseSearchIndex(*Table, Class->getValue(Field),
-                                                Name, {Field}, false));
+                                                Name, {Field}, false, false));
     }
 
     Tables.emplace_back(std::move(Table));
