[clang] 830a740 - [Clang] [Cygwin] va_list must be treated like normal Windows (#143115)

[via cfe-commits]

Author: Tomohiro Kashiwada
Date: 2025-06-10T23:42:36+03:00
New Revision: 830a74092adafa425db05e1c5120d3294f874777

URL: https://github.com/llvm/llvm-project/commit/830a74092adafa425db05e1c5120d3294f874777
DIFF: https://github.com/llvm/llvm-project/commit/830a74092adafa425db05e1c5120d3294f874777.diff

LOG: [Clang] [Cygwin] va_list must be treated like normal Windows (#143115)

Handling of va_list on Cygwin environment must be matched to normal
Windows environment.

The existing test `test/CodeGen/ms_abi.c` seems relevant, but it
contains `__attribute__((sysv_abi))`, which is not supported on Cygwin.
The new test is based on the `__attribute__((ms_abi))` portion of that
test.

---------

Co-authored-by: jeremyd2019 <github at jdrake.com>

Added: 
    clang/test/CodeGen/X86/cygwin-varargs.c

Modified: 
    clang/lib/Basic/Targets/X86.h

Removed: 
    


################################################################################
diff  --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h
index 6f8a2365be256..ecb31ffa4750f 100644
--- a/clang/lib/Basic/Targets/X86.h
+++ b/clang/lib/Basic/Targets/X86.h
@@ -997,6 +997,10 @@ class LLVM_LIBRARY_VISIBILITY CygwinX86_64TargetInfo : public X86_64TargetInfo {
     if (Opts.CPlusPlus)
       Builder.defineMacro("_GNU_SOURCE");
   }
+
+  BuiltinVaListKind getBuiltinVaListKind() const override {
+    return TargetInfo::CharPtrBuiltinVaList;
+  }
 };
 
 class LLVM_LIBRARY_VISIBILITY DarwinX86_64TargetInfo

diff  --git a/clang/test/CodeGen/X86/cygwin-varargs.c b/clang/test/CodeGen/X86/cygwin-varargs.c
new file mode 100644
index 0000000000000..4eea7d64bcb35
--- /dev/null
+++ b/clang/test/CodeGen/X86/cygwin-varargs.c
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -triple x86_64-windows-gnu -emit-llvm < %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-pc-cygwin -emit-llvm < %s | FileCheck %s
+
+struct foo {
+  int x;
+  float y;
+  char z;
+};
+// CHECK: %[[STRUCT_FOO:.*]] = type { i32, float, i8 }
+
+void f(int a, ...) {
+  // CHECK-LABEL: define dso_local void @f
+  __builtin_va_list ap;
+  __builtin_va_start(ap, a);
+  // CHECK: %[[AP:.*]] = alloca ptr
+  // CHECK: call void @llvm.va_start
+  int b = __builtin_va_arg(ap, int);
+  // CHECK: %[[AP_CUR:.*]] = load ptr, ptr %[[AP]]
+  // CHECK-NEXT: %[[AP_NEXT:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR]], i64 8
+  // CHECK-NEXT: store ptr %[[AP_NEXT]], ptr %[[AP]]
+  double _Complex c = __builtin_va_arg(ap, double _Complex);
+  // CHECK: %[[AP_CUR2:.*]] = load ptr, ptr %[[AP]]
+  // CHECK-NEXT: %[[AP_NEXT2:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR2]], i64 8
+  // CHECK-NEXT: store ptr %[[AP_NEXT2]], ptr %[[AP]]
+  // CHECK-NEXT: load ptr, ptr %[[AP_CUR2]]
+  struct foo d = __builtin_va_arg(ap, struct foo);
+  // CHECK: %[[AP_CUR3:.*]] = load ptr, ptr %[[AP]]
+  // CHECK-NEXT: %[[AP_NEXT3:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR3]], i64 8
+  // CHECK-NEXT: store ptr %[[AP_NEXT3]], ptr %[[AP]]
+  __builtin_va_list ap2;
+  __builtin_va_copy(ap2, ap);
+  // CHECK: call void @llvm.va_copy
+  __builtin_va_end(ap);
+  // CHECK: call void @llvm.va_end
+}