Implement an al::unreachable wrapper/helper

3 files changed, 22 insertions, 11 deletions

diff --git a/al/buffer.cpp b/al/buffer.cpp
index 6deb3788..21520cec 100644
--- a/al/buffer.cpp
+++ b/al/buffer.cpp
@@ -1096,7 +1096,7 @@ START_API_FUNC
     ALuint align{SanitizeAlignment(usrfmt->type, unpack_align)};
     if(align < 1) [[unlikely]]
         context->setError(AL_INVALID_VALUE, "Invalid unpack alignment %u", unpack_align);
-    else if(long{usrfmt->channels} != long{albuf->mChannels}
+    else if(al::to_underlying(usrfmt->channels) != al::to_underlying(albuf->mChannels)
         || usrfmt->type != albuf->OriginalType) [[unlikely]]
         context->setError(AL_INVALID_ENUM, "Unpacking data with mismatched format");
     else if(align != albuf->OriginalAlign) [[unlikely]]
@@ -1145,7 +1145,7 @@ START_API_FUNC
                     static_cast<const al::byte*>(data), num_chans, samplen, align);
             else
             {
-                assert(long{usrfmt->type} == long{albuf->mType});
+                assert(al::to_underlying(usrfmt->type) == al::to_underlying(albuf->mType));
                 memcpy(dst, data, size_t{samplen} * frame_size);
             }
         }
diff --git a/alc/alu.cpp b/alc/alu.cpp
index dc5ed122..fdb51f78 100644
--- a/alc/alu.cpp
+++ b/alc/alu.cpp
@@ -1714,7 +1714,7 @@ void SendSourceStateEvent(ContextBase *context, uint id, VChangeState state)
         break;
     /* Shouldn't happen. */
     case VChangeState::Restart:
-        ASSUME(0);
+        al::unreachable();
     }
 
     ring->writeAdvance(1);
diff --git a/common/opthelpers.h b/common/opthelpers.h
index f6d9cc00..04c5f1d0 100644
--- a/common/opthelpers.h
+++ b/common/opthelpers.h
@@ -30,7 +30,7 @@
 #define ASSUME __assume
 #elif __has_attribute(assume)
 #define ASSUME(x) [[assume(x)]]
-#elif defined(__GNUC__)
+#elif HAS_BUILTIN(__builtin_unreachable)
 #define ASSUME(x) do { if(x) break; __builtin_unreachable(); } while(0)
 #else
 #define ASSUME(x) ((void)0)
@@ -38,23 +38,34 @@
 
 namespace al {
 
+template<typename T>
+constexpr std::underlying_type_t<T> to_underlying(T e) noexcept
+{ return static_cast<std::underlying_type_t<T>>(e); }
+
+[[noreturn]] inline void unreachable()
+{
+#if HAS_BUILTIN(__builtin_unreachable)
+    __builtin_unreachable();
+#else
+    ASSUME(false);
+#endif
+}
+
 template<std::size_t alignment, typename T>
 force_inline constexpr auto assume_aligned(T *ptr) noexcept
 {
 #ifdef __cpp_lib_assume_aligned
     return std::assume_aligned<alignment,T>(ptr);
-#elif defined(__clang__) || (defined(__GNUC__) && !defined(__ICC))
+#elif HAS_BUILTIN(__builtin_assume_aligned)
     return static_cast<T*>(__builtin_assume_aligned(ptr, alignment));
-#elif defined(_MSC_VER)
-    constexpr std::size_t alignment_mask{(1<<alignment) - 1};
-    if((reinterpret_cast<std::uintptr_t>(ptr)&alignment_mask) == 0)
-        return ptr;
-    __assume(0);
 #elif defined(__ICC)
     __assume_aligned(ptr, alignment);
     return ptr;
 #else
-    return ptr;
+    constexpr std::size_t alignment_mask{(1<<alignment) - 1};
+    if((reinterpret_cast<std::uintptr_t>(ptr)&alignment_mask) == 0)
+        return ptr;
+    unreachable();
 #endif
 }