[PATCH v3 5/6] MdePkg/Include: Add VA list support for VS2017/ARM

[Pete Batard <pete@akeo.ie>]

VA_START, VA_END and VA_COPY are the same as the generic macros.
VA_ARG was reverse engineered from MS ARM assembly output.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Pete Batard <pete@akeo.ie>
---
 MdePkg/Include/Base.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/MdePkg/Include/Base.h b/MdePkg/Include/Base.h
index 02140a5ac2ee..f3467ecdc22f 100644
--- a/MdePkg/Include/Base.h
+++ b/MdePkg/Include/Base.h
@@ -631,6 +631,19 @@ struct _LIST_ENTRY {
 
 #define VA_COPY(Dest, Start)          __va_copy (Dest, Start)
 
+#elif defined(_M_ARM)
+//
+// MSFT ARM variable argument list support.
+// Same as the generic macros below, except for VA_ARG that needs extra adjustment.
+//
+
+typedef char* VA_LIST;
+
+#define VA_START(Marker, Parameter)     (Marker = (VA_LIST) ((UINTN) & (Parameter) + _INT_SIZE_OF(Parameter)))
+#define VA_ARG(Marker, TYPE)            (*(TYPE *) ((Marker += _INT_SIZE_OF(TYPE) + ((-(INTN)Marker) & (sizeof(TYPE) - 1))) - _INT_SIZE_OF (TYPE)))
+#define VA_END(Marker)                  (Marker = (VA_LIST) 0)
+#define VA_COPY(Dest, Start)            ((void)((Dest) = (Start)))
+
 #elif defined(__GNUC__)
 
 #if defined(MDE_CPU_X64) && !defined(NO_MSABI_VA_FUNCS)
-- 
2.9.3.windows.2