[llvm-branch-commits] [clang] release/21.x: [WIP] [clang] Align cleanup structs to prevent SIGBUS on sparc32 (#152866) (PR #154002)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/154002

Backport 8071d279fd97134f798699795dfb0b16747ce247

Requested by: @brad0

>From 4747623231d1a59e7c538d28e045ee27a4065379 Mon Sep 17 00:00:00 2001
From: Koakuma <koachan at protonmail.com>
Date: Wed, 13 Aug 2025 23:26:36 +0700
Subject: [PATCH] [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: https://github.com/llvm/llvm-project/issues/66620

(cherry picked from commit 8071d279fd97134f798699795dfb0b16747ce247)
---
 clang/include/clang/AST/APValue.h   | 2 +-
 clang/lib/CodeGen/CodeGenFunction.h | 5 +++--
 clang/lib/CodeGen/EHScopeStack.h    | 2 +-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/AST/APValue.h b/clang/include/clang/AST/APValue.h
index 9999a30c51ade..cb942ea865e2d 100644
--- a/clang/include/clang/AST/APValue.h
+++ b/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;
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 6c32c98cec011..f5ac9f387c641 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -727,7 +727,7 @@ 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.
@@ -949,7 +949,8 @@ 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);
diff --git a/clang/lib/CodeGen/EHScopeStack.h b/clang/lib/CodeGen/EHScopeStack.h
index ed11dc2bb05d7..54f6ceaa52b95 100644
--- a/clang/lib/CodeGen/EHScopeStack.h
+++ b/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();