Revert "[Modules] Record whether VarDecl initializers contain side effects" (#145407)

Reverts llvm/llvm-project#143739 because it triggers an assert:

```
Assertion failed: (!isNull() && "Cannot retrieve a NULL type pointer"), function getCommonPtr, file Type.h, line 952.
```

3 files changed, 6 insertions, 15 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 6f082fe..a3fbc3d 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -9722,10 +9722,6 @@ bool ASTReader::wasThisDeclarationADefinition(const FunctionDecl *FD) {
   return ThisDeclarationWasADefinitionSet.contains(FD);
 }
 
-bool ASTReader::hasInitializerWithSideEffects(const VarDecl *VD) const {
-  return InitSideEffectVars.count(VD);
-}
-
 Selector ASTReader::getLocalSelector(ModuleFile &M, unsigned LocalID) {
   return DecodeSelector(getGlobalSelectorID(M, LocalID));
 }
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 0ffd784..7f78826 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1628,9 +1628,6 @@ RedeclarableResult ASTDeclReader::VisitVarDeclImpl(VarDecl *VD) {
     VD->NonParmVarDeclBits.PreviousDeclInSameBlockScope =
         VarDeclBits.getNextBit();
 
-    if (VarDeclBits.getNextBit())
-      Reader.InitSideEffectVars.insert(VD);
-
     VD->NonParmVarDeclBits.EscapingByref = VarDeclBits.getNextBit();
     HasDeducedType = VarDeclBits.getNextBit();
     VD->NonParmVarDeclBits.ImplicitParamKind =
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 2e390db..2d93832 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -1306,7 +1306,6 @@ void ASTDeclWriter::VisitVarDecl(VarDecl *D) {
     VarDeclBits.addBit(D->isConstexpr());
     VarDeclBits.addBit(D->isInitCapture());
     VarDeclBits.addBit(D->isPreviousDeclInSameBlockScope());
-    VarDeclBits.addBit(D->hasInitWithSideEffects());
 
     VarDeclBits.addBit(D->isEscapingByref());
     HasDeducedType = D->getType()->getContainedDeducedType();
@@ -1356,11 +1355,10 @@ void ASTDeclWriter::VisitVarDecl(VarDecl *D) {
       !D->hasExtInfo() && D->getFirstDecl() == D->getMostRecentDecl() &&
       D->getKind() == Decl::Var && !D->isInline() && !D->isConstexpr() &&
       !D->isInitCapture() && !D->isPreviousDeclInSameBlockScope() &&
-      !D->hasInitWithSideEffects() && !D->isEscapingByref() &&
-      !HasDeducedType && D->getStorageDuration() != SD_Static &&
-      !D->getDescribedVarTemplate() && !D->getMemberSpecializationInfo() &&
-      !D->isObjCForDecl() && !isa<ImplicitParamDecl>(D) &&
-      !D->isEscapingByref())
+      !D->isEscapingByref() && !HasDeducedType &&
+      D->getStorageDuration() != SD_Static && !D->getDescribedVarTemplate() &&
+      !D->getMemberSpecializationInfo() && !D->isObjCForDecl() &&
+      !isa<ImplicitParamDecl>(D) && !D->isEscapingByref())
     AbbrevToUse = Writer.getDeclVarAbbrev();
 
   Code = serialization::DECL_VAR;
@@ -2733,12 +2731,12 @@ void ASTWriter::WriteDeclAbbrevs() {
   // VarDecl
   Abv->Add(BitCodeAbbrevOp(
       BitCodeAbbrevOp::Fixed,
-      22)); // Packed Var Decl bits:  Linkage, ModulesCodegen,
+      21)); // Packed Var Decl bits:  Linkage, ModulesCodegen,
             // SClass, TSCSpec, InitStyle,
             // isARCPseudoStrong, IsThisDeclarationADemotedDefinition,
             // isExceptionVariable, isNRVOVariable, isCXXForRangeDecl,
             // isInline, isInlineSpecified, isConstexpr,
-            // isInitCapture, isPrevDeclInSameScope, hasInitWithSideEffects,
+            // isInitCapture, isPrevDeclInSameScope,
             // EscapingByref, HasDeducedType, ImplicitParamKind, isObjCForDecl
   Abv->Add(BitCodeAbbrevOp(0));                         // VarKind (local enum)
   // Type Source Info