[clang] [ObjC] Fix jmp_buf sizing for ObjC exceptions (PR #85481)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-codegen

Author: AtariDreams (AtariDreams)

<details>
<summary>Changes</summary>

The size of 18 only works for x86, but does not work for the other architectures. This works for Darwin and was retrieved via reading the setjmp.h header. It would be nice if we could do the equivalent of sizeof() that would obtain the size as though it were being run on the target, not the host, but this is the best I could do for now.

---
Full diff: https://github.com/llvm/llvm-project/pull/85481.diff


1 Files Affected:

- (modified) clang/lib/CodeGen/CGObjCMac.cpp (+27-6) 


``````````diff
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index e815e097e1fb48..340e99ab5b94c4 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -587,9 +587,9 @@ class ObjCTypesHelper : public ObjCCommonTypesHelper {
   /// SetJmpFn - LLVM _setjmp function.
   llvm::FunctionCallee getSetJmpFn() {
     // This is specifically the prototype for x86.
-    llvm::Type *params[] = { CGM.Int32Ty->getPointerTo() };
+    llvm::Type *params[] = {CGM.IntTy->getPointerTo()};
     return CGM.CreateRuntimeFunction(
-        llvm::FunctionType::get(CGM.Int32Ty, params, false), "_setjmp",
+        llvm::FunctionType::get(CGM.IntTy, params, false), "_setjmp",
         llvm::AttributeList::get(CGM.getLLVMContext(),
                                  llvm::AttributeList::FunctionIndex,
                                  llvm::Attribute::NonLazyBind));
@@ -5946,16 +5946,37 @@ ObjCTypesHelper::ObjCTypesHelper(CodeGen::CodeGenModule &cgm)
   ModuleTy = llvm::StructType::create("struct._objc_module", LongTy, LongTy,
                                       Int8PtrTy, SymtabPtrTy);
 
-  // FIXME: This is the size of the setjmp buffer and should be target
-  // specific. 18 is what's used on 32-bit X86.
-  uint64_t SetJmpBufferSize = 18;
+  // FIXME: Not a perfect solution, but one that better fits the other
+  // architectures Values are derived from setjmp.h on Darwin
+  uint64_t SetJmpBufferSize = 0;
+  switch (CGM.getTarget().getTriple().getArch()) {
+  case llvm::Triple::arm:
+    if (CGM.getTarget().getTriple().getSubArch() !=
+        llvm::Triple::ARMSubArch_v7k) {
+      SetJmpBufferSize = (10 + 16 + 2);
+      break;
+    }
+    [[fallthrough]];
+  case llvm::Triple::aarch64:
+    SetJmpBufferSize = ((14 + 8 + 2) * 2);
+    break;
+  case llvm::Triple::x86_64:
+    SetJmpBufferSize = ((9 * 2) + 3 + 16); // Obtained from macOS's setjmp.h
+    break;
+  case llvm::Triple::x86:
+  default:
+    // 18 is what's used on 32-bit X86 and on all architectures on prior
+    // versions of clang.
+    SetJmpBufferSize = 18;
+    break;
+  }
 
   // Exceptions
   llvm::Type *StackPtrTy = llvm::ArrayType::get(CGM.Int8PtrTy, 4);
 
   ExceptionDataTy = llvm::StructType::create(
       "struct._objc_exception_data",
-      llvm::ArrayType::get(CGM.Int32Ty, SetJmpBufferSize), StackPtrTy);
+      llvm::ArrayType::get(CGM.IntTy, SetJmpBufferSize), StackPtrTy);
 }
 
 ObjCNonFragileABITypesHelper::ObjCNonFragileABITypesHelper(CodeGen::CodeGenModule &cgm)

``````````

</details>


https://github.com/llvm/llvm-project/pull/85481