[llvm-branch-commits] [llvm] Add a GUIDLIST table to bitcode (PR #139497)

[Owen Rodley via llvm-branch-commits]

https://github.com/orodley created https://github.com/llvm/llvm-project/pull/139497

None

>From bfb6cb21243f043ea1edf6f00cf27d08549066dc Mon Sep 17 00:00:00 2001
From: Owen Rodley <orodley at google.com>
Date: Mon, 12 May 2025 15:50:22 +1000
Subject: [PATCH] Add a GUIDLIST table to bitcode

---
 llvm/include/llvm/Bitcode/LLVMBitCodes.h  |  3 +++
 llvm/lib/Bitcode/Reader/BitcodeReader.cpp | 11 +++++++---
 llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | 25 +++++++++++++++++++++++
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
index 92b6e68d9d0a7..8acba6477c4a1 100644
--- a/llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -120,6 +120,9 @@ enum ModuleCodes {
 
   // IFUNC: [ifunc value type, addrspace, resolver val#, linkage, visibility]
   MODULE_CODE_IFUNC = 18,
+
+  // GUIDLIST: [n x i64]
+  MODULE_CODE_GUIDLIST = 19,
 };
 
 /// PARAMATTR blocks have code for defining a parameter attribute set.
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 1d7aa189026a5..6d36b007956a0 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -980,6 +980,9 @@ class ModuleSummaryIndexBitcodeReader : public BitcodeReaderBase {
   /// the CallStackRadixTreeBuilder class in ProfileData/MemProf.h for format.
   std::vector<uint64_t> RadixArray;
 
+  // A table which maps ValueID to the GUID for that value.
+  std::vector<uint64_t> DefinedGUIDs;
+
 public:
   ModuleSummaryIndexBitcodeReader(
       BitstreamCursor Stream, StringRef Strtab, ModuleSummaryIndex &TheIndex,
@@ -7164,9 +7167,7 @@ ModuleSummaryIndexBitcodeReader::getValueInfoFromValueId(unsigned ValueId) {
 void ModuleSummaryIndexBitcodeReader::setValueGUID(
     uint64_t ValueID, StringRef ValueName, GlobalValue::LinkageTypes Linkage,
     StringRef SourceFileName) {
-  std::string GlobalId =
-      GlobalValue::getGlobalIdentifier(ValueName, Linkage, SourceFileName);
-  auto ValueGUID = GlobalValue::getGUIDAssumingExternalLinkage(GlobalId);
+  auto ValueGUID = DefinedGUIDs[ValueID];
   auto OriginalNameID = ValueGUID;
   if (GlobalValue::isLocalLinkage(Linkage))
     OriginalNameID = GlobalValue::getGUIDAssumingExternalLinkage(ValueName);
@@ -7389,6 +7390,10 @@ Error ModuleSummaryIndexBitcodeReader::parseModule() {
           // was historically always the start of the regular bitcode header.
           VSTOffset = Record[0] - 1;
           break;
+        // MODULE_CODE_GUIDLIST: [i64 x N]
+        case bitc::MODULE_CODE_GUIDLIST:
+          llvm::append_range(DefinedGUIDs, Record);
+          break;
         // v1 GLOBALVAR: [pointer type, isconst,     initid,       linkage, ...]
         // v1 FUNCTION:  [type,         callingconv, isproto,      linkage, ...]
         // v1 ALIAS:     [alias type,   addrspace,   aliasee val#, linkage, ...]
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 73bed85c65b3d..3e19220d1bde7 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -227,6 +227,7 @@ class ModuleBitcodeWriterBase : public BitcodeWriterBase {
 
 protected:
   void writePerModuleGlobalValueSummary();
+  void writeGUIDList();
 
 private:
   void writePerModuleFunctionSummaryRecord(
@@ -1560,6 +1561,8 @@ void ModuleBitcodeWriter::writeModuleInfo() {
     Vals.clear();
   }
 
+  writeGUIDList();
+
   // Emit the global variable information.
   for (const GlobalVariable &GV : M.globals()) {
     unsigned AbbrevToUse = 0;
@@ -4755,6 +4758,26 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
   Stream.ExitBlock();
 }
 
+void ModuleBitcodeWriterBase::writeGUIDList() {
+  std::vector<uint64_t> GUIDs;
+  GUIDs.reserve(M.global_size() + M.size() + M.alias_size());
+
+  for (const GlobalValue &GV : M.global_objects()) {
+    if (GV.isDeclaration()) {
+      GUIDs.push_back(
+          GlobalValue::getGUIDAssumingExternalLinkage(GV.getName()));
+    } else {
+      GUIDs.push_back(GV.getGUID());
+    }
+  }
+  for (const GlobalAlias &GA : M.aliases()) {
+    // Equivalent to the above loop, as GlobalAliases are always definitions.
+    GUIDs.push_back(GA.getGUID());
+  }
+
+  Stream.EmitRecord(bitc::MODULE_CODE_GUIDLIST, GUIDs);
+}
+
 /// Emit the combined summary section into the combined index file.
 void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
   Stream.EnterSubblock(bitc::GLOBALVAL_SUMMARY_BLOCK_ID, 4);
@@ -5538,6 +5561,8 @@ void ThinLinkBitcodeWriter::writeSimplifiedModuleInfo() {
     Vals.clear();
   }
 
+  writeGUIDList();
+
   // Emit the global variable information.
   for (const GlobalVariable &GV : M.globals()) {
     // GLOBALVAR: [strtab offset, strtab size, 0, 0, 0, linkage]