[llvm] [NFC][Bitcode] Remove FUNCTION_INST_UNOP abbrevs (PR #146717)

[Orlando Cazalet-Hyams via llvm-commits]

https://github.com/OCHyams updated https://github.com/llvm/llvm-project/pull/146717

>From d233243c42e4b49212bfc57bb971ff54e1771bf3 Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Wed, 2 Jul 2025 11:15:49 +0100
Subject: [PATCH 1/2] [NFC][Bitcode] Remove FUNCTION_INST_UNOP abbrevs

Discussed in #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.
---
 llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | 37 ++++++++++-------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 2a2dd085a9461..64fbc1b9eb271 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/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>();

>From dce4850978aecd48d43b084b3b85658703b14329 Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Wed, 2 Jul 2025 16:06:03 +0100
Subject: [PATCH 2/2] rm

---
 llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 64fbc1b9eb271..c1191d964a60c 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -3941,25 +3941,6 @@ void ModuleBitcodeWriter::writeBlockInfo() {
         FUNCTION_INST_LOAD_ABBREV)
       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!");
-  }
-  { // 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!");
-  }
   { // INST_BINOP abbrev for FUNCTION_BLOCK.
     auto Abbv = std::make_shared<BitCodeAbbrev>();
     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));