From c0af478dfd07ae267dd957a490ffe9f2cc234d1b Mon Sep 17 00:00:00 2001
From: Stenzek <stenzek@gmail.com>
Date: Sun, 3 Sep 2023 14:42:37 +1000
Subject: [PATCH] Common: Add ASSUME() and use for UnreachableCode()

---
 src/common/assert.cpp |  6 +++++-
 src/common/assert.h   | 12 ++++++++----
 src/common/types.h    |  7 +++++++
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/common/assert.cpp b/src/common/assert.cpp
index 9a959b315..60e5b1d47 100644
--- a/src/common/assert.cpp
+++ b/src/common/assert.cpp
@@ -12,6 +12,10 @@
 #include <tlhelp32.h>
 #endif
 
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Winvalid-noreturn"
+#endif
+
 static std::mutex s_AssertFailedMutex;
 
 static inline void FreezeThreads(void** ppHandle)
@@ -107,7 +111,7 @@ void Y_OnAssertFailed(const char* szMessage, const char* szFunction, const char*
   ResumeThreads(pHandle);
 }
 
-void Y_OnPanicReached(const char* szMessage, const char* szFunction, const char* szFile, unsigned uLine)
+[[noreturn]] void Y_OnPanicReached(const char* szMessage, const char* szFunction, const char* szFile, unsigned uLine)
 {
   std::lock_guard<std::mutex> guard(s_AssertFailedMutex);
 
diff --git a/src/common/assert.h b/src/common/assert.h
index 51589d0fb..3455dfc78 100644
--- a/src/common/assert.h
+++ b/src/common/assert.h
@@ -1,10 +1,12 @@
-// SPDX-FileCopyrightText: 2019-2022 Connor McLaughlin <stenzek@gmail.com>
+// SPDX-FileCopyrightText: 2019-2023 Connor McLaughlin <stenzek@gmail.com>
 // SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)
 
 #pragma once
 
+#include "types.h"
+
 void Y_OnAssertFailed(const char* szMessage, const char* szFunction, const char* szFile, unsigned uLine);
-void Y_OnPanicReached(const char* szMessage, const char* szFunction, const char* szFile, unsigned uLine);
+[[noreturn]] void Y_OnPanicReached(const char* szMessage, const char* szFunction, const char* szFile, unsigned uLine);
 
 #define Assert(expr)                                                                                                   \
   if (!(expr))                                                                                                         \
@@ -28,11 +30,9 @@ void Y_OnPanicReached(const char* szMessage, const char* szFunction, const char*
   {                                                                                                                    \
     Y_OnAssertFailed("Debug assertion failed: '" msg "'", __FUNCTION__, __FILE__, __LINE__);                           \
   }
-#define DebugUnreachableCode() Y_OnPanicReached("Unreachable code reached", __FUNCTION__, __FILE__, __LINE__)
 #else
 #define DebugAssert(expr)
 #define DebugAssertMsg(expr, msg)
-#define DebugUnreachableCode()
 #endif
 
 // Panics the application, displaying an error message.
@@ -41,8 +41,12 @@ void Y_OnPanicReached(const char* szMessage, const char* szFunction, const char*
 // Kills the application, indicating a pure function call that should not have happened.
 #define PureCall() Y_OnPanicReached("PureCall encountered", __FUNCTION__, __FILE__, __LINE__)
 
+#ifdef _DEBUG
 // Kills the application, indicating that code that was never supposed to be reached has been executed.
 #define UnreachableCode() Y_OnPanicReached("Unreachable code reached", __FUNCTION__, __FILE__, __LINE__)
+#else
+#define UnreachableCode() ASSUME(false)
+#endif
 
 // Helper for switch cases.
 #define DefaultCaseIsUnreachable()                                                                                     \
diff --git a/src/common/types.h b/src/common/types.h
index 5f78668a6..0d0d11eb7 100644
--- a/src/common/types.h
+++ b/src/common/types.h
@@ -73,6 +73,13 @@ char (&__countof_ArraySizeHelper(T (&array)[N]))[N];
 #define NORETURN_FUNCTION_POINTER __attribute__((noreturn))
 #endif
 
+// __assume, potentially enables optimization.
+#ifdef _MSC_VER
+#define ASSUME(x) __assume(x)
+#else
+#define ASSUME(x) do { if (!(x)) __builtin_unreachable(); } while(0)
+#endif
+
 // disable warnings that show up at warning level 4
 // TODO: Move to build system instead
 #ifdef _MSC_VER