[clang] 5b1eed6 - [WinEH] Fix crash when aligning parameters larger than ABI (#180905)

[via cfe-commits]

Author: GkvJwa
Date: 2026-03-12T10:53:32+08:00
New Revision: 5b1eed6278de1fffa195978b017039add70a94e3

URL: https://github.com/llvm/llvm-project/commit/5b1eed6278de1fffa195978b017039add70a94e3
DIFF: https://github.com/llvm/llvm-project/commit/5b1eed6278de1fffa195978b017039add70a94e3.diff

LOG: [WinEH] Fix crash when aligning parameters larger than ABI (#180905)

Fix #180648 caused by an unhandled `Argument` for parameters exceeding
ABI size limits. This patch explicitly emits an `alloca` for the `Argument` in 
the entry block to ensure correct address resolution.

Added: 
    clang/test/CodeGen/windows-seh-arg-capture-crash.cpp

Modified: 
    clang/lib/CodeGen/CGException.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/CodeGen/CGException.cpp b/clang/lib/CodeGen/CGException.cpp
index 98bc6ea34b0bc..1437bc2d32159 100644
--- a/clang/lib/CodeGen/CGException.cpp
+++ b/clang/lib/CodeGen/CGException.cpp
@@ -1834,10 +1834,27 @@ struct CaptureFinder : ConstStmtVisitor<CaptureFinder> {
 Address CodeGenFunction::recoverAddrOfEscapedLocal(CodeGenFunction &ParentCGF,
                                                    Address ParentVar,
                                                    llvm::Value *ParentFP) {
-  llvm::CallInst *RecoverCall = nullptr;
+  llvm::Value *RecoverCall = nullptr;
   CGBuilderTy Builder(CGM, AllocaInsertPt);
-  if (auto *ParentAlloca =
-          dyn_cast_or_null<llvm::AllocaInst>(ParentVar.getBasePointer())) {
+  // We are currently handling the following case:
+  // ParentAlloca: An alloca for a local variable/direct argument
+  // ParentArg: An argument pointer, pointing to an argument passed indirectly
+  // Other case: A call to localrecover, if this is a nested __try.
+  auto *ParentAlloca =
+      dyn_cast_or_null<llvm::AllocaInst>(ParentVar.getBasePointer());
+  auto *ParentArg =
+      dyn_cast_or_null<llvm::Argument>(ParentVar.getBasePointer());
+  if (!ParentAlloca) {
+    if (ParentArg) {
+      llvm::BasicBlock &EntryBB = ParentCGF.CurFn->getEntryBlock();
+      llvm::IRBuilder<> ParentEntryBuilder(&EntryBB, EntryBB.begin());
+      ParentAlloca = ParentEntryBuilder.CreateAlloca(
+          ParentArg->getType(), nullptr, ParentArg->getName() + ".spill");
+      ParentEntryBuilder.CreateStore(ParentArg, ParentAlloca);
+    }
+  }
+
+  if (ParentAlloca) {
     // Mark the variable escaped if nobody else referenced it and compute the
     // localescape index.
     auto InsertPair = ParentCGF.EscapedLocals.insert(
@@ -1849,7 +1866,9 @@ Address CodeGenFunction::recoverAddrOfEscapedLocal(CodeGenFunction &ParentCGF,
     RecoverCall = Builder.CreateCall(
         FrameRecoverFn, {ParentCGF.CurFn, ParentFP,
                          llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)});
-
+    if (ParentArg)
+      RecoverCall = Builder.CreateLoad(
+          Address(RecoverCall, ParentArg->getType(), getPointerAlign()));
   } else {
     // If the parent didn't have an alloca, we're doing some nested outlining.
     // Just clone the existing localrecover call, but tweak the FP argument to
@@ -1858,9 +1877,10 @@ Address CodeGenFunction::recoverAddrOfEscapedLocal(CodeGenFunction &ParentCGF,
         ParentVar.emitRawPointer(*this)->stripPointerCasts());
     assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::localrecover &&
            "expected alloca or localrecover in parent LocalDeclMap");
-    RecoverCall = cast<llvm::CallInst>(ParentRecover->clone());
-    RecoverCall->setArgOperand(1, ParentFP);
-    RecoverCall->insertBefore(AllocaInsertPt->getIterator());
+    RecoverCall = ParentRecover->clone();
+    cast<llvm::CallInst>(RecoverCall)->setArgOperand(1, ParentFP);
+    cast<llvm::CallInst>(RecoverCall)
+        ->insertBefore(AllocaInsertPt->getIterator());
   }
 
   // Bitcast the variable, rename it, and insert it in the local decl map.

diff  --git a/clang/test/CodeGen/windows-seh-arg-capture-crash.cpp b/clang/test/CodeGen/windows-seh-arg-capture-crash.cpp
new file mode 100644
index 0000000000000..089d966c86969
--- /dev/null
+++ b/clang/test/CodeGen/windows-seh-arg-capture-crash.cpp
@@ -0,0 +1,56 @@
+// RUN: %clang_cc1 -triple x86_64-pc-windows-msvc -fms-extensions -fexceptions -emit-llvm -o - %s | FileCheck %s
+
+class span_a {
+ public:
+  char data_;
+  int size_;
+};
+
+long g(span_a input);
+
+void f(span_a input) {
+  __try {
+  } __except (g(input)) {
+  }
+}
+
+// CHECK-LABEL: define dso_local void @"?f@@YAXVspan_a@@@Z"(i64 %input.coerce)
+// CHECK: entry:
+// CHECK:   call void (...) @llvm.localescape(ptr %input)
+
+// CHECK-LABEL: define internal noundef i32 @"?filt$0 at 0@f@@"(ptr noundef %exception_pointers
+// CHECK: entry:
+// CHECK:   %frame_pointer.addr = alloca ptr, align 8
+// CHECK:   %exception_pointers.addr = alloca ptr, align 8
+// CHECK:   %0 = call ptr @llvm.eh.recoverfp(ptr @"?f@@YAXVspan_a@@@Z", ptr %frame_pointer)
+// CHECK:   %input = call ptr @llvm.localrecover(ptr @"?f@@YAXVspan_a@@@Z", ptr %0, i32 0)
+
+
+typedef __SIZE_TYPE__ size_t;
+
+class span_b {
+ public:
+  char data_;
+  size_t size_;
+};
+
+long g(span_b input);
+
+void f(span_b input) {
+  __try {
+  } __except (g(input)) {
+  }
+}
+
+// CHECK-LABEL: define dso_local void @"?f@@YAXVspan_b@@@Z"(ptr noundef dead_on_return %input)
+// CHECK: entry:
+// CHECK:   %input.spill = alloca ptr, align 8
+// CHECK:   call void (...) @llvm.localescape(ptr %input.spill)
+
+// CHECK-LABEL: define internal noundef i32 @"?filt$0 at 0@f@@.1"(ptr noundef %exception_pointers
+// CHECK: entry:
+// CHECK:   %frame_pointer.addr = alloca ptr, align 8
+// CHECK:   %exception_pointers.addr = alloca ptr, align 8
+// CHECK:   %0 = call ptr @llvm.eh.recoverfp(ptr @"?f@@YAXVspan_b@@@Z", ptr %frame_pointer)
+// CHECK:   %1 = call ptr @llvm.localrecover(ptr @"?f@@YAXVspan_b@@@Z", ptr %0, i32 0)
+// CHECK:   %input = load ptr, ptr %1, align 8