compiler.h changes for Windows MSVC support (#6623)

Summary:
Adding some MSVC (Windows) specific macros to compiler.h to make sure we can build with MSVC.



Reviewed By: dbort

Differential Revision: D65328573

Author: tarun292

kernels/prim_ops/register_prim_ops.cpp

@@ -148,7 +148,7 @@ static Kernel prim_ops[] = {
           EValue& out = *stack[2];
           if (a.isInt() && b.isInt()) {
             const int64_t quot = a.toInt() / b.toInt();
-            if (std::signbit(a.toInt()) == std::signbit(b.toInt())) {
+            if ((a.toInt() < 0) == (b.toInt() < 0)) {
               out = EValue(quot);
               return;
             }

runtime/executor/memory_manager.h

@@ -67,11 +67,7 @@ class MemoryManager final {
    * TODO(T162089316): Remove this once all users migrate to the new ctor.
    */
   ET_DEPRECATED MemoryManager(
-      // We would normally use ET_UNUSED here, but GCC older than 9.3 has a
-      // bug that triggers a syntax error when using [[maybe_unused]] on the
-      // first parameter of a constructor:
-      // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81429
-      __attribute__((unused)) MemoryAllocator* constant_allocator,
+      ET_UNUSED MemoryAllocator* constant_allocator,
       HierarchicalAllocator* non_constant_allocator,
       MemoryAllocator* runtime_allocator,
       MemoryAllocator* temporary_allocator)

runtime/executor/program.cpp

@@ -27,8 +27,6 @@
 #define ET_ENABLE_PROGRAM_VERIFICATION 1
 #endif
 
-#pragma clang diagnostic ignored "-Wshadow"
-
 namespace executorch {
 namespace runtime {
 

runtime/platform/compiler.h

@@ -80,7 +80,15 @@
   [[deprecated("This API is experimental and may change without notice.")]]
 #define ET_FALLTHROUGH [[fallthrough]]
 #define ET_NODISCARD [[nodiscard]]
+
+#if defined(__GNUC__) && (__GNUC__ < 9 || (__GNUC__ == 9 && __GNUC_MINOR__ < 3))
+// GCC older than 9.3 has a bug that triggers a syntax error when using [[maybe_unused]]
+// on the first parameter of a constructor:
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81429
+#define ET_UNUSED __attribute__((unused))
+#else
 #define ET_UNUSED [[maybe_unused]]
+#endif
 
 // UNLIKELY Macro
 // example
@@ -100,22 +108,38 @@
 #endif // (__cplusplus) >= 202002L
 
 /// Define a C symbol with weak linkage.
+#ifdef _WIN32
+// There currently doesn't seem to be a great way to do this in Windows and given
+// that weak linkage is not really critical on Windows, we'll just leave it as a stub.
+#define ET_WEAK
+#else
 #define ET_WEAK __attribute__((weak))
+#endif
 
 /**
  * Annotation marking a function as printf-like, providing compiler support
  * for format string argument checking.
  */
+#ifdef _WIN32
+#include <sal.h>
+#define ET_PRINTFLIKE(_string_index, _va_index) _Printf_format_string_
+#else
 #define ET_PRINTFLIKE(_string_index, _va_index) \
   __attribute__((format(printf, _string_index, _va_index)))
-
-/// Name of the source file without a directory string.
-#define ET_SHORT_FILENAME (__builtin_strrchr("/" __FILE__, '/') + 1)
+#endif
 
 #ifndef __has_builtin
 #define __has_builtin(x) (0)
 #endif
 
+#if __has_builtin(__builtin_strrchr)
+/// Name of the source file without a directory string.
+#define ET_SHORT_FILENAME (__builtin_strrchr("/" __FILE__, '/') + 1)
+#else
+#include <cstring>
+#define ET_SHORT_FILENAME (strchr("/" __FILE__, '/') + 1)
+#endif
+
 #if __has_builtin(__builtin_LINE)
 /// Current line as an integer.
 #define ET_LINE __builtin_LINE()