[NFC][Bitcode] Remove FUNCTION_INST_UNOP abbrevs

Discussed in llvm#146497.

Seems to have a positive impact on bitcode file size in CTMark LTO builds, and
makes space for more abbrevs without bumping the CodeLen for function blocks.

Alternatively, we could just bump the CodeLen to 5 bits.

Author: OCHyams

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -141,8 +141,6 @@ enum {
 
   // FUNCTION_BLOCK abbrev id's.
   FUNCTION_INST_LOAD_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
-  FUNCTION_INST_UNOP_ABBREV,
-  FUNCTION_INST_UNOP_FLAGS_ABBREV,
   FUNCTION_INST_BINOP_ABBREV,
   FUNCTION_INST_BINOP_FLAGS_ABBREV,
   FUNCTION_INST_CAST_ABBREV,
@@ -3127,13 +3125,10 @@ void ModuleBitcodeWriter::writeInstruction(const Instruction &I,
     break;
   case Instruction::FNeg: {
     Code = bitc::FUNC_CODE_INST_UNOP;
-    if (!pushValueAndType(I.getOperand(0), InstID, Vals))
-      AbbrevToUse = FUNCTION_INST_UNOP_ABBREV;
+    pushValueAndType(I.getOperand(0), InstID, Vals);
     Vals.push_back(getEncodedUnaryOpcode(I.getOpcode()));
     uint64_t Flags = getOptimizationFlags(&I);
     if (Flags != 0) {
-      if (AbbrevToUse == FUNCTION_INST_UNOP_ABBREV)
-        AbbrevToUse = FUNCTION_INST_UNOP_FLAGS_ABBREV;
       Vals.push_back(Flags);
     }
     break;
@@ -3947,23 +3942,23 @@ void ModuleBitcodeWriter::writeBlockInfo() {
       llvm_unreachable("Unexpected abbrev ordering!");
   }
   { // INST_UNOP abbrev for FUNCTION_BLOCK.
-    auto Abbv = std::make_shared<BitCodeAbbrev>();
-    Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNOP));
-    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
-    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
-    if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID, Abbv) !=
-        FUNCTION_INST_UNOP_ABBREV)
-      llvm_unreachable("Unexpected abbrev ordering!");
+    // auto Abbv = std::make_shared<BitCodeAbbrev>();
+    // Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNOP));
+    // Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
+    // Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
+    // if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID, Abbv) !=
+    //     FUNCTION_INST_UNOP_ABBREV)
+    //   llvm_unreachable("Unexpected abbrev ordering!");
   }
   { // INST_UNOP_FLAGS abbrev for FUNCTION_BLOCK.
-    auto Abbv = std::make_shared<BitCodeAbbrev>();
-    Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNOP));
-    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
-    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
-    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8)); // flags
-    if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID, Abbv) !=
-        FUNCTION_INST_UNOP_FLAGS_ABBREV)
-      llvm_unreachable("Unexpected abbrev ordering!");
+    // auto Abbv = std::make_shared<BitCodeAbbrev>();
+    // Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNOP));
+    // Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
+    // Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
+    // Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8)); // flags
+    // if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID, Abbv) !=
+    //     FUNCTION_INST_UNOP_FLAGS_ABBREV)
+    //   llvm_unreachable("Unexpected abbrev ordering!");
   }
   { // INST_BINOP abbrev for FUNCTION_BLOCK.
     auto Abbv = std::make_shared<BitCodeAbbrev>();