[LLVM][TableGen] Move DecoderEmitter output to anonymous namespace (#136214)

- Move the code generated by DecoderEmitter to anonymous namespace.
- Move AMDGPU's usage of this code from header file to .cpp file.

Note, we get build errors like "call to function 'decodeInstruction'
that is neither visible in the template definition nor found by
argument-dependent lookup" if we do not change AMDGPU.

Author: jurahul

llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp

@@ -487,6 +487,46 @@ static DecodeStatus decodeVersionImm(MCInst &Inst, unsigned Imm,
 //
 //===----------------------------------------------------------------------===//
 
+template <typename InsnType>
+DecodeStatus AMDGPUDisassembler::tryDecodeInst(const uint8_t *Table, MCInst &MI,
+                                               InsnType Inst, uint64_t Address,
+                                               raw_ostream &Comments) const {
+  assert(MI.getOpcode() == 0);
+  assert(MI.getNumOperands() == 0);
+  MCInst TmpInst;
+  HasLiteral = false;
+  const auto SavedBytes = Bytes;
+
+  SmallString<64> LocalComments;
+  raw_svector_ostream LocalCommentStream(LocalComments);
+  CommentStream = &LocalCommentStream;
+
+  DecodeStatus Res =
+      decodeInstruction(Table, TmpInst, Inst, Address, this, STI);
+
+  CommentStream = nullptr;
+
+  if (Res != MCDisassembler::Fail) {
+    MI = TmpInst;
+    Comments << LocalComments;
+    return MCDisassembler::Success;
+  }
+  Bytes = SavedBytes;
+  return MCDisassembler::Fail;
+}
+
+template <typename InsnType>
+DecodeStatus
+AMDGPUDisassembler::tryDecodeInst(const uint8_t *Table1, const uint8_t *Table2,
+                                  MCInst &MI, InsnType Inst, uint64_t Address,
+                                  raw_ostream &Comments) const {
+  for (const uint8_t *T : {Table1, Table2}) {
+    if (DecodeStatus Res = tryDecodeInst(T, MI, Inst, Address, Comments))
+      return Res;
+  }
+  return MCDisassembler::Fail;
+}
+
 template <typename T> static inline T eatBytes(ArrayRef<uint8_t>& Bytes) {
   assert(Bytes.size() >= sizeof(T));
   const auto Res =

llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.h

@@ -130,41 +130,11 @@ class AMDGPUDisassembler : public MCDisassembler {
 
   template <typename InsnType>
   DecodeStatus tryDecodeInst(const uint8_t *Table, MCInst &MI, InsnType Inst,
-                             uint64_t Address, raw_ostream &Comments) const {
-    assert(MI.getOpcode() == 0);
-    assert(MI.getNumOperands() == 0);
-    MCInst TmpInst;
-    HasLiteral = false;
-    const auto SavedBytes = Bytes;
-
-    SmallString<64> LocalComments;
-    raw_svector_ostream LocalCommentStream(LocalComments);
-    CommentStream = &LocalCommentStream;
-
-    DecodeStatus Res =
-        decodeInstruction(Table, TmpInst, Inst, Address, this, STI);
-
-    CommentStream = nullptr;
-
-    if (Res != Fail) {
-      MI = TmpInst;
-      Comments << LocalComments;
-      return MCDisassembler::Success;
-    }
-    Bytes = SavedBytes;
-    return MCDisassembler::Fail;
-  }
-
+                             uint64_t Address, raw_ostream &Comments) const;
   template <typename InsnType>
   DecodeStatus tryDecodeInst(const uint8_t *Table1, const uint8_t *Table2,
                              MCInst &MI, InsnType Inst, uint64_t Address,
-                             raw_ostream &Comments) const {
-    for (const uint8_t *T : {Table1, Table2}) {
-      if (DecodeStatus Res = tryDecodeInst(T, MI, Inst, Address, Comments))
-        return Res;
-    }
-    return MCDisassembler::Fail;
-  }
+                             raw_ostream &Comments) const;
 
   Expected<bool> onSymbolStart(SymbolInfoTy &Symbol, uint64_t &Size,
                                ArrayRef<uint8_t> Bytes,

llvm/utils/TableGen/DecoderEmitter.cpp

@@ -2417,7 +2417,7 @@ void DecoderEmitter::run(raw_ostream &o) {
 #include "llvm/TargetParser/SubtargetFeature.h"
 #include <assert.h>
 
-namespace llvm {
+namespace {
 )";
 
   emitFieldFromInstruction(OS);
@@ -2561,7 +2561,7 @@ namespace llvm {
   // Emit the main entry point for the decoder, decodeInstruction().
   emitDecodeInstruction(OS, IsVarLenInst);
 
-  OS << "\n} // end namespace llvm\n";
+  OS << "\n} // namespace\n";
 }
 
 void llvm::EmitDecoder(const RecordKeeper &RK, raw_ostream &OS,