[PATCH] D138511: [CodeGen][AArch64] Fix AArch64ABIInfo::EmitAAPCSVAArg crash with empty record type in variadic arg

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Fix AArch64ABIInfo::EmitAAPCSVAArg crash with empty record type in variadic arg

Open issue: https://github.com/llvm/llvm-project/issues/59034


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D138511

Files:
  clang/lib/CodeGen/TargetInfo.cpp
  clang/test/CodeGen/aarch64-varargs.c


Index: clang/test/CodeGen/aarch64-varargs.c
===================================================================
--- clang/test/CodeGen/aarch64-varargs.c
+++ clang/test/CodeGen/aarch64-varargs.c
@@ -894,4 +894,10 @@
 // CHECK: call void @llvm.va_start(i8* [[VOIDP_THE_LIST]])
 }
 
-
+typedef struct {} empty;
+empty empty_record_test(void) {
+// CHECK-LABEL: define{{.*}} void @empty_record_test()
+  return va_arg(the_list, empty);
+// CHECK: [[GR_OFFS:%[a-z_0-9]+]] = load i8*, i8** getelementptr inbounds (%struct.__va_list, %struct.__va_list* @the_list, i32 0, i32 0)
+// CHECK: [[ADDR:%[a-z._0-9]+]] = bitcast i8* [[GR_OFFS]] to %struct.empty*
+}
Index: clang/lib/CodeGen/TargetInfo.cpp
===================================================================
--- clang/lib/CodeGen/TargetInfo.cpp
+++ clang/lib/CodeGen/TargetInfo.cpp
@@ -5995,6 +5995,17 @@
 
 Address AArch64ABIInfo::EmitAAPCSVAArg(Address VAListAddr, QualType Ty,
                                        CodeGenFunction &CGF) const {
+  uint64_t PointerSize = getTarget().getPointerWidth(0) / 8;
+  CharUnits SlotSize = CharUnits::fromQuantity(PointerSize);
+
+  // Empty records are ignored for parameter passing purposes.
+  if (isEmptyRecord(getContext(), Ty, true)) {
+    VAListAddr = CGF.Builder.CreateElementBitCast(VAListAddr, CGF.Int8PtrTy);
+    auto *Load = CGF.Builder.CreateLoad(VAListAddr);
+    Address Addr = Address(Load, CGF.Int8Ty, SlotSize);
+    return CGF.Builder.CreateElementBitCast(Addr, CGF.ConvertTypeForMem(Ty));
+  }
+
   ABIArgInfo AI = classifyArgumentType(Ty, /*IsVariadic=*/true,
                                        CGF.CurFnInfo->getCallingConvention());
   bool IsIndirect = AI.isIndirect();


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