[reland][NFC] Transition GlobalObject alignment from MaybeAlign to Align

This is a follow up on https://reviews.llvm.org/D142459#4081179.
This first patch adds an overload to `GlobalObject::setAlignment` that accepts an `Align` type.
This already handles most of the calls.

This patch also converts a few call sites to the new type when this is safe.

Here is the list of the remaining call sites:

 - [clang/lib/CodeGen/CodeGenModule.cpp:1688](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/clang/lib/CodeGen/CodeGenModule.cpp#L1688)
 - [llvm/lib/AsmParser/LLParser.cpp:1309](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/AsmParser/LLParser.cpp#L1309)
 - [llvm/lib/AsmParser/LLParser.cpp:6050](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/AsmParser/LLParser.cpp#L6050)
 - [llvm/lib/Bitcode/Reader/BitcodeReader.cpp:3871](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/Bitcode/Reader/BitcodeReader.cpp#L3871)
 - [llvm/lib/Bitcode/Reader/BitcodeReader.cpp:4030](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/Bitcode/Reader/BitcodeReader.cpp#L4030)
 - [llvm/lib/IR/Core.cpp:2018](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/IR/Core.cpp#L2018)
 - [llvm/lib/IR/Globals.cpp:141](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/IR/Globals.cpp#L141)
 - [llvm/lib/Linker/IRMover.cpp:660](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/Linker/IRMover.cpp#L660)
 - [llvm/lib/Linker/LinkModules.cpp:361](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/Linker/LinkModules.cpp#L361)
 - [llvm/lib/Linker/LinkModules.cpp:362](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/Linker/LinkModules.cpp#L362)
 - [llvm/lib/Transforms/IPO/MergeFunctions.cpp:782](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/Transforms/IPO/MergeFunctions.cpp#L782)
 - [llvm/lib/Transforms/IPO/MergeFunctions.cpp:840](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/Transforms/IPO/MergeFunctions.cpp#L840)
 - [llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp:1813](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp#L1813)
 - [llvm/tools/llvm-reduce/deltas/ReduceGlobalObjects.cpp:27](https://github.com/llvm/llvm-project/blob/e195e6bad6706230a4b5fd4b5cc13de1f16f25cc/llvm/tools/llvm-reduce/deltas/ReduceGlobalObjects.cpp#L27)

Differential Revision: https://reviews.llvm.org/D142708

Author: gchatelet

llvm/include/llvm/IR/GlobalObject.h

@@ -82,6 +82,12 @@ class GlobalObject : public GlobalValue {
     return decodeMaybeAlign(AlignmentData);
   }
 
+  /// Sets the alignment attribute of the GlobalObject.
+  void setAlignment(Align Align);
+
+  /// Sets the alignment attribute of the GlobalObject.
+  /// This method will be deprecated as the alignment property should always be
+  /// defined.
   void setAlignment(MaybeAlign Align);
 
   unsigned getGlobalObjectSubClassData() const {

llvm/include/llvm/LTO/LTO.h

@@ -289,7 +289,7 @@ class LTO {
                     const Config &Conf);
     struct CommonResolution {
       uint64_t Size = 0;
-      MaybeAlign Align;
+      Align Alignment;
       /// Record if at least one instance of the common was marked as prevailing
       bool Prevailing = false;
     };

llvm/lib/AsmParser/LLParser.cpp

@@ -150,7 +150,7 @@ bool LLParser::validateEndOfModule(bool UpgradeDebugInfo) {
       // If the alignment was parsed as an attribute, move to the alignment
       // field.
       if (MaybeAlign A = FnAttrs.getAlignment()) {
-        Fn->setAlignment(A);
+        Fn->setAlignment(*A);
         FnAttrs.removeAttribute(Attribute::Alignment);
       }
 
@@ -6047,7 +6047,7 @@ bool LLParser::parseFunctionHeader(Function *&Fn, bool IsDefine) {
   Fn->setCallingConv(CC);
   Fn->setAttributes(PAL);
   Fn->setUnnamedAddr(UnnamedAddr);
-  Fn->setAlignment(MaybeAlign(Alignment));
+  Fn->setAlignment(Alignment);
   Fn->setSection(Section);
   Fn->setPartition(Partition);
   Fn->setComdat(C);

llvm/lib/IR/Globals.cpp

@@ -127,6 +127,16 @@ void GlobalObject::setAlignment(MaybeAlign Align) {
   assert(getAlign() == Align && "Alignment representation error!");
 }
 
+void GlobalObject::setAlignment(Align Align) {
+  assert(Align <= MaximumAlignment &&
+         "Alignment is greater than MaximumAlignment!");
+  unsigned AlignmentData = encode(Align);
+  unsigned OldData = getGlobalValueSubClassData();
+  setGlobalValueSubClassData((OldData & ~AlignmentMask) | AlignmentData);
+  assert(getAlign() && *getAlign() == Align &&
+         "Alignment representation error!");
+}
+
 void GlobalObject::copyAttributesFrom(const GlobalObject *Src) {
   GlobalValue::copyAttributesFrom(Src);
   setAlignment(Src->getAlign());

llvm/lib/LTO/LTO.cpp

@@ -839,8 +839,8 @@ LTO::addRegularLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
       auto &CommonRes = RegularLTO.Commons[std::string(Sym.getIRName())];
       CommonRes.Size = std::max(CommonRes.Size, Sym.getCommonSize());
       if (uint32_t SymAlignValue = Sym.getCommonAlignment()) {
-        const Align SymAlign(SymAlignValue);
-        CommonRes.Align = std::max(SymAlign, CommonRes.Align.valueOrOne());
+        CommonRes.Alignment =
+            std::max(Align(SymAlignValue), CommonRes.Alignment);
       }
       CommonRes.Prevailing |= Res.Prevailing;
     }
@@ -1116,15 +1116,15 @@ Error LTO::runRegularLTO(AddStreamFn AddStream) {
     if (OldGV && DL.getTypeAllocSize(OldGV->getValueType()) == I.second.Size) {
       // Don't create a new global if the type is already correct, just make
       // sure the alignment is correct.
-      OldGV->setAlignment(I.second.Align);
+      OldGV->setAlignment(I.second.Alignment);
       continue;
     }
     ArrayType *Ty =
         ArrayType::get(Type::getInt8Ty(RegularLTO.Ctx), I.second.Size);
     auto *GV = new GlobalVariable(*RegularLTO.CombinedModule, Ty, false,
                                   GlobalValue::CommonLinkage,
                                   ConstantAggregateZero::get(Ty), "");
-    GV->setAlignment(I.second.Align);
+    GV->setAlignment(I.second.Alignment);
     if (OldGV) {
       OldGV->replaceAllUsesWith(ConstantExpr::getBitCast(GV, OldGV->getType()));
       GV->takeName(OldGV);

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

@@ -3300,7 +3300,7 @@ struct AAHeapToSharedFunction : public AAHeapToShared {
       MaybeAlign Alignment = CB->getRetAlign();
       assert(Alignment &&
              "HeapToShared on allocation without alignment attribute");
-      SharedMem->setAlignment(MaybeAlign(Alignment));
+      SharedMem->setAlignment(*Alignment);
 
       A.changeAfterManifest(IRPosition::callsite_returned(*CB), *NewBuffer);
       A.deleteAfterManifest(*CB);

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -2306,7 +2306,7 @@ bool ModuleAddressSanitizer::InstrumentGlobals(IRBuilder<> &IRB, Module &M,
         G->getThreadLocalMode(), G->getAddressSpace());
     NewGlobal->copyAttributesFrom(G);
     NewGlobal->setComdat(G->getComdat());
-    NewGlobal->setAlignment(MaybeAlign(getMinRedzoneSizeForGlobal()));
+    NewGlobal->setAlignment(Align(getMinRedzoneSizeForGlobal()));
     // Don't fold globals with redzones. ODR violation detector and redzone
     // poisoning implicitly creates a dependence on the global's address, so it
     // is no longer valid for it to be marked unnamed_addr.