[LLVM][TableGen] Change WebAsm Emitter to use const RecordKeeper (#109051)

Change WebAssemblyDisassemblerEmitter to use const RecordKeeper.

This is a part of effort to have better const correctness in TableGen
backends:


https://discourse.llvm.org/t/psa-planned-changes-to-tablegen-getallderiveddefinitions-api-potential-downstream-breakages/81089

Author: jurahul

llvm/include/llvm/TableGen/Record.h

@@ -603,6 +603,7 @@ class BitsInit final : public TypedInit, public FoldingSetNode,
 
   Init *convertInitializerTo(RecTy *Ty) const override;
   Init *convertInitializerBitRange(ArrayRef<unsigned> Bits) const override;
+  std::optional<int64_t> convertInitializerToInt() const;
 
   bool isComplete() const override {
     for (unsigned i = 0; i != getNumBits(); ++i)

llvm/lib/TableGen/Record.cpp

@@ -497,18 +497,24 @@ Init *BitsInit::convertInitializerTo(RecTy *Ty) const {
   }
 
   if (isa<IntRecTy>(Ty)) {
-    int64_t Result = 0;
-    for (unsigned i = 0, e = getNumBits(); i != e; ++i)
-      if (auto *Bit = dyn_cast<BitInit>(getBit(i)))
-        Result |= static_cast<int64_t>(Bit->getValue()) << i;
-      else
-        return nullptr;
-    return IntInit::get(getRecordKeeper(), Result);
+    std::optional<int64_t> Result = convertInitializerToInt();
+    if (Result)
+      return IntInit::get(getRecordKeeper(), *Result);
   }
 
   return nullptr;
 }
 
+std::optional<int64_t> BitsInit::convertInitializerToInt() const {
+  int64_t Result = 0;
+  for (unsigned i = 0, e = getNumBits(); i != e; ++i)
+    if (auto *Bit = dyn_cast<BitInit>(getBit(i)))
+      Result |= static_cast<int64_t>(Bit->getValue()) << i;
+    else
+      return std::nullopt;
+  return Result;
+}
+
 Init *
 BitsInit::convertInitializerBitRange(ArrayRef<unsigned> Bits) const {
   SmallVector<Init *, 16> NewBits(Bits.size());

llvm/utils/TableGen/WebAssemblyDisassemblerEmitter.cpp

@@ -19,28 +19,23 @@
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TableGen/Record.h"
 
-namespace llvm {
-
 static constexpr int WebAssemblyInstructionTableSize = 256;
 
-void emitWebAssemblyDisassemblerTables(
+void llvm::emitWebAssemblyDisassemblerTables(
     raw_ostream &OS,
-    const ArrayRef<const CodeGenInstruction *> &NumberedInstructions) {
+    ArrayRef<const CodeGenInstruction *> NumberedInstructions) {
   // First lets organize all opcodes by (prefix) byte. Prefix 0 is the
   // starting table.
   std::map<unsigned,
            std::map<unsigned, std::pair<unsigned, const CodeGenInstruction *>>>
       OpcodeTable;
   for (unsigned I = 0; I != NumberedInstructions.size(); ++I) {
-    auto &CGI = *NumberedInstructions[I];
-    auto &Def = *CGI.TheDef;
+    const CodeGenInstruction &CGI = *NumberedInstructions[I];
+    const Record &Def = *CGI.TheDef;
     if (!Def.getValue("Inst"))
       continue;
-    auto &Inst = *Def.getValueAsBitsInit("Inst");
-    RecordKeeper &RK = Inst.getRecordKeeper();
-    unsigned Opc = static_cast<unsigned>(
-        cast<IntInit>(Inst.convertInitializerTo(IntRecTy::get(RK)))
-            ->getValue());
+    const BitsInit &Inst = *Def.getValueAsBitsInit("Inst");
+    unsigned Opc = static_cast<unsigned>(*Inst.convertInitializerToInt());
     if (Opc == 0xFFFFFFFF)
       continue; // No opcode defined.
     assert(Opc <= 0xFFFFFF);
@@ -97,14 +92,14 @@ void emitWebAssemblyDisassemblerTables(
   OS << "};\n\n";
   std::vector<std::string> OperandTable, CurOperandList;
   // Output one table per prefix.
-  for (auto &PrefixPair : OpcodeTable) {
-    if (PrefixPair.second.empty())
+  for (const auto &[Prefix, Table] : OpcodeTable) {
+    if (Table.empty())
       continue;
-    OS << "WebAssemblyInstruction InstructionTable" << PrefixPair.first;
+    OS << "WebAssemblyInstruction InstructionTable" << Prefix;
     OS << "[] = {\n";
     for (unsigned I = 0; I < WebAssemblyInstructionTableSize; I++) {
-      auto InstIt = PrefixPair.second.find(I);
-      if (InstIt != PrefixPair.second.end()) {
+      auto InstIt = Table.find(I);
+      if (InstIt != Table.end()) {
         // Regular instruction.
         assert(InstIt->second.second);
         auto &CGI = *InstIt->second.second;
@@ -144,7 +139,7 @@ void emitWebAssemblyDisassemblerTables(
       } else {
         auto PrefixIt = OpcodeTable.find(I);
         // If we have a non-empty table for it that's not 0, this is a prefix.
-        if (PrefixIt != OpcodeTable.end() && I && !PrefixPair.first) {
+        if (PrefixIt != OpcodeTable.end() && I && !Prefix) {
           OS << "  { 0, ET_Prefix, 0, 0";
         } else {
           OS << "  { 0, ET_Unused, 0, 0";
@@ -163,15 +158,11 @@ void emitWebAssemblyDisassemblerTables(
   // Create a table of all extension tables:
   OS << "struct { uint8_t Prefix; const WebAssemblyInstruction *Table; }\n";
   OS << "PrefixTable[] = {\n";
-  for (auto &PrefixPair : OpcodeTable) {
-    if (PrefixPair.second.empty() || !PrefixPair.first)
+  for (const auto &[Prefix, Table] : OpcodeTable) {
+    if (Table.empty() || !Prefix)
       continue;
-    OS << "  { " << PrefixPair.first << ", InstructionTable"
-       << PrefixPair.first;
-    OS << " },\n";
+    OS << "  { " << Prefix << ", InstructionTable" << Prefix << " },\n";
   }
   OS << "  { 0, nullptr }\n};\n\n";
   OS << "} // end namespace llvm\n";
 }
-
-} // namespace llvm

llvm/utils/TableGen/WebAssemblyDisassemblerEmitter.h

@@ -22,8 +22,7 @@ class CodeGenInstruction;
 class raw_ostream;
 
 void emitWebAssemblyDisassemblerTables(
-    raw_ostream &OS,
-    const ArrayRef<const CodeGenInstruction *> &NumberedInstructions);
+    raw_ostream &OS, ArrayRef<const CodeGenInstruction *> NumberedInstructions);
 
 } // namespace llvm