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

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Koakuma (koachan)

<details>
<summary>Changes</summary>

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

---
Full diff: https://github.com/llvm/llvm-project/pull/152866.diff


3 Files Affected:

- (modified) clang/include/clang/AST/APValue.h (+1-1) 
- (modified) clang/lib/CodeGen/CodeGenFunction.h (+3-2) 
- (modified) clang/lib/CodeGen/EHScopeStack.h (+1-1) 


``````````diff
diff --git a/clang/include/clang/AST/APValue.h b/clang/include/clang/AST/APValue.h
index 9999a30c51ade..167fa7078d028 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(8) 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 bf16d727bac04..393c5161177df 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -725,7 +725,7 @@ class CodeGenFunction : public CodeGenTypeCache {
   };
 
   /// Header for data within LifetimeExtendedCleanupStack.
-  struct LifetimeExtendedCleanupHeader {
+  struct alignas(8) 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);
diff --git a/clang/lib/CodeGen/EHScopeStack.h b/clang/lib/CodeGen/EHScopeStack.h
index ed11dc2bb05d7..1a9cff48ad852 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(8) Cleanup {
     // Anchor the construction vtable.
     virtual void anchor();
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/152866