[HeaderSearch] Introduce LazyIdentifierInfoPtr for Controlling Macro in HeaderFileInfo

This patch is helpful to reduce 32 bits for HeaderFileInfo by combining
a uint32_t and pointer into a tagged pointer.

This is reviewed as part of
https://github.com/llvm/llvm-project/pull/92085 and required to be split
as a separate commit

3 files changed, 21 insertions, 21 deletions

diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 9321a36..3bd3aa4 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -60,19 +60,21 @@ ALWAYS_ENABLED_STATISTIC(NumSubFrameworkLookups,
 
 const IdentifierInfo *
 HeaderFileInfo::getControllingMacro(ExternalPreprocessorSource *External) {
-  if (ControllingMacro) {
-    if (ControllingMacro->isOutOfDate()) {
-      assert(External && "We must have an external source if we have a "
-                         "controlling macro that is out of date.");
-      External->updateOutOfDateIdentifier(*ControllingMacro);
-    }
-    return ControllingMacro;
-  }
+  if (LazyControllingMacro.isID()) {
+    if (!External)
+      return nullptr;
 
-  if (!ControllingMacroID || !External)
-    return nullptr;
+    LazyControllingMacro =
+        External->GetIdentifier(LazyControllingMacro.getID());
+    return LazyControllingMacro.getPtr();
+  }
 
-  ControllingMacro = External->GetIdentifier(ControllingMacroID);
+  IdentifierInfo *ControllingMacro = LazyControllingMacro.getPtr();
+  if (ControllingMacro && ControllingMacro->isOutOfDate()) {
+    assert(External && "We must have an external source if we have a "
+                       "controlling macro that is out of date.");
+    External->updateOutOfDateIdentifier(*ControllingMacro);
+  }
   return ControllingMacro;
 }
 
@@ -1348,10 +1350,8 @@ static void mergeHeaderFileInfo(HeaderFileInfo &HFI,
   mergeHeaderFileInfoModuleBits(HFI, OtherHFI.isModuleHeader,
                                 OtherHFI.isTextualModuleHeader);
 
-  if (!HFI.ControllingMacro && !HFI.ControllingMacroID) {
-    HFI.ControllingMacro = OtherHFI.ControllingMacro;
-    HFI.ControllingMacroID = OtherHFI.ControllingMacroID;
-  }
+  if (!HFI.LazyControllingMacro.isValid())
+    HFI.LazyControllingMacro = OtherHFI.LazyControllingMacro;
 
   HFI.DirInfo = OtherHFI.DirInfo;
   HFI.External = (!HFI.IsValid || HFI.External);
@@ -1426,8 +1426,7 @@ bool HeaderSearch::isFileMultipleIncludeGuarded(FileEntryRef File) const {
   // once. Note that we dor't check for #import, because that's not a property
   // of the file itself.
   if (auto *HFI = getExistingFileInfo(File))
-    return HFI->isPragmaOnce || HFI->ControllingMacro ||
-           HFI->ControllingMacroID;
+    return HFI->isPragmaOnce || HFI->LazyControllingMacro.isValid();
   return false;
 }
 
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 973475c..0afbc44 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2092,7 +2092,7 @@ HeaderFileInfoTrait::ReadData(internal_key_ref key, const unsigned char *d,
   HFI.isPragmaOnce |= (Flags >> 4) & 0x01;
   HFI.DirInfo = (Flags >> 1) & 0x07;
   HFI.IndexHeaderMapHeader = Flags & 0x01;
-  HFI.ControllingMacroID = Reader.getGlobalIdentifierID(
+  HFI.LazyControllingMacro = Reader.getGlobalIdentifierID(
       M, endian::readNext<uint32_t, llvm::endianness::little>(d));
   if (unsigned FrameworkOffset =
           endian::readNext<uint32_t, llvm::endianness::little>(d)) {
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 50fa44d..a60092a 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -2028,10 +2028,11 @@ namespace {
                           | Data.HFI.IndexHeaderMapHeader;
       LE.write<uint8_t>(Flags);
 
-      if (!Data.HFI.ControllingMacro)
-        LE.write<uint32_t>(Data.HFI.ControllingMacroID);
+      if (Data.HFI.LazyControllingMacro.isID())
+        LE.write<IdentifierID>(Data.HFI.LazyControllingMacro.getID());
       else
-        LE.write<uint32_t>(Writer.getIdentifierRef(Data.HFI.ControllingMacro));
+        LE.write<IdentifierID>(
+            Writer.getIdentifierRef(Data.HFI.LazyControllingMacro.getPtr()));
 
       unsigned Offset = 0;
       if (!Data.HFI.Framework.empty()) {