[clang] [SYCL][SPIR-V] Implement fix for Windows/MSVC SPIR-V device target support (PR #208196)

[via cfe-commits]

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@@ -0,0 +1,41 @@
+/// Tests that getBuiltinVaListKind() delegates to the host target, verified
+/// via sizeof(__builtin_va_list) and struct layout containing va_list.
+
+// RUN: %clang_cc1 -triple spirv64-unknown-unknown -aux-triple x86_64-unknown-linux-gnu \
+// RUN:   -fsycl-is-device -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple spirv64-unknown-unknown -aux-triple x86_64-pc-windows-msvc \
+// RUN:   -fsycl-is-device -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple spirv64-unknown-unknown -aux-triple aarch64-unknown-linux-gnu \
+// RUN:   -fsycl-is-device -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple spirv64-unknown-unknown \
+// RUN:   -fsycl-is-device -fsyntax-only -verify %s
+
+// expected-no-diagnostics
+
+struct has_valist { int x; __builtin_va_list ap; int y; };
+
+#if defined(_WIN32)
+// Windows x86_64: CharPtrBuiltinVaList (char*)
+static_assert(sizeof(__builtin_va_list) == 8, "Windows: va_list is char*");
+static_assert(sizeof(has_valist) == 24, "Windows: struct layout with char* va_list");
+static_assert(__builtin_offsetof(has_valist, y) == 16,
+              "Windows: field after char* va_list");
+#elif defined(__aarch64__)
+// AArch64 Linux: AArch64ABIBuiltinVaList (struct, 32 bytes)
+static_assert(sizeof(__builtin_va_list) == 32, "AArch64: va_list is struct");
+static_assert(sizeof(has_valist) == 48, "AArch64: struct layout with 32-byte va_list");
+static_assert(__builtin_offsetof(has_valist, y) == 40,
+              "AArch64: field after 32-byte va_list");
+#elif defined(__x86_64__)
+// x86_64 Linux: X86_64ABIBuiltinVaList (struct __va_list_tag, 24 bytes)
+static_assert(sizeof(__builtin_va_list) == 24, "Linux x86_64: va_list is struct");
+static_assert(sizeof(has_valist) == 40, "Linux x86_64: struct layout with 24-byte va_list");
+static_assert(__builtin_offsetof(has_valist, y) == 32,
+              "Linux x86_64: field after 24-byte va_list");
+#else
+// No host: VoidPtrBuiltinVaList (void*)
+static_assert(sizeof(__builtin_va_list) == 8, "No host: va_list is void*");
+static_assert(sizeof(has_valist) == 24, "No host: struct layout with void* va_list");
+static_assert(__builtin_offsetof(has_valist, y) == 16,
+              "No host: field after void* va_list");
+#endif
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schittir wrote:

Are you suggesting that I add a similar test for SPIR too, i.e., spir-host-adaptation-valist.cpp? It doesn't exist in the current state of the patch. 

https://github.com/llvm/llvm-project/pull/208196