[WIP] [clang] Align cleanup structs to prevent SIGBUS on sparc32 (#152866)

The cleanup structs expect that pointers and (u)int64_t have the same
alignment requirements, which isn't true on sparc32, which causes
SIGBUSes.

See also: #66620

Author: koachan

clang/include/clang/AST/APValue.h

@@ -143,7 +143,7 @@ class APValue {
     AddrLabelDiff
   };
 
-  class LValueBase {
+  class alignas(uint64_t) LValueBase {
     typedef llvm::PointerUnion<const ValueDecl *, const Expr *, TypeInfoLValue,
                                DynamicAllocLValue>
         PtrTy;

clang/lib/CodeGen/CodeGenFunction.h

@@ -725,7 +725,7 @@ class CodeGenFunction : public CodeGenTypeCache {
   };
 
   /// Header for data within LifetimeExtendedCleanupStack.
-  struct LifetimeExtendedCleanupHeader {
+  struct alignas(uint64_t) LifetimeExtendedCleanupHeader {
     /// The size of the following cleanup object.
     unsigned Size;
     /// The kind of cleanup to push.
@@ -947,7 +947,8 @@ class CodeGenFunction : public CodeGenTypeCache {
         LifetimeExtendedCleanupStack.size() + sizeof(Header) + Header.Size +
         (Header.IsConditional ? sizeof(ActiveFlag) : 0));
 
-    static_assert(sizeof(Header) % alignof(T) == 0,
+    static_assert((alignof(LifetimeExtendedCleanupHeader) == alignof(T)) &&
+                      (alignof(T) == alignof(RawAddress)),
                   "Cleanup will be allocated on misaligned address");
     char *Buffer = &LifetimeExtendedCleanupStack[OldSize];
     new (Buffer) LifetimeExtendedCleanupHeader(Header);

clang/lib/CodeGen/EHScopeStack.h

@@ -143,7 +143,7 @@ class EHScopeStack {
   ///
   /// Cleanup implementations should generally be declared in an
   /// anonymous namespace.
-  class Cleanup {
+  class alignas(uint64_t) Cleanup {
     // Anchor the construction vtable.
     virtual void anchor();