diff --git a/Sources/Core/Debug.h b/Sources/Core/Debug.h
index 16af52473..893dc7ecc 100644
--- a/Sources/Core/Debug.h
+++ b/Sources/Core/Debug.h
@@ -102,6 +102,12 @@ namespace spades {
 #define __PRETTY_FUNCTION__ __FUNCDNAME__
 #endif
 
+#if defined(__GNUC__) && defined(__GNUC_MINOR__)
+#define GCCVERSION (__GNUC__ * 1000 + __GNUC_MINOR__)
+#else
+#define GCCVERSION 0
+#endif
+
 #define SPADES_MARK_FUNCTION()                                                                     \
 	static constexpr ::spades::reflection::Function thisFunction{__PRETTY_FUNCTION__, __FILE__,    \
 	                                                             __LINE__};                        \
@@ -124,6 +130,23 @@ namespace spades {
 #define SPAssert(cond) ((!(cond)) ? SPRaise("SPAssertion failed: %s", #cond) : (void)0)
 #endif
 
+#if NDEBUG
+#ifdef _MSC_VER
+#define SPAssume(cond) __assume(cond)
+#elif defined(__clang__) && __clang_major__ > 3
+#define SPAssume(cond) __builtin_assume(cond)
+#elif defined(__GNUC__) && GCCVERSION >= 4005
+#define SPAssume(cond)                                                                             \
+	do {                                                                                          \
+		if (!(cond)) __builtin_unreachable();                                                      \
+	} while (0)
+#else
+#define SPAssume(cond)
+#endif
+#else
+#define SPAssume(cond) SPAssert(cond)
+#endif
+
 #ifdef _MSC_VER
 #define SPLog(format, ...) ::spades::LogMessage(__FILE__, __LINE__, format, __VA_ARGS__)
 #else
diff --git a/Sources/Draw/SWImageRenderer.cpp b/Sources/Draw/SWImageRenderer.cpp
index d46e45d0d..d328ff51e 100644
--- a/Sources/Draw/SWImageRenderer.cpp
+++ b/Sources/Draw/SWImageRenderer.cpp
@@ -410,7 +410,7 @@ namespace spades {
 					if (depthTest) {
 						depthOut = depthBuffer + (y * fbW);
 					}
-					SPAssert(x1 < x2);
+					SPAssume(x1 < x2);
 					int width = x2 - x1;
 					SWImageGouraudInterpolator<level> vary(vary1, vary2, width);
 					int minX = std::max(x1, 0);
diff --git a/Sources/Draw/SWModelRenderer.cpp b/Sources/Draw/SWModelRenderer.cpp
index c7703b360..14e50120a 100644
--- a/Sources/Draw/SWModelRenderer.cpp
+++ b/Sources/Draw/SWModelRenderer.cpp
@@ -189,7 +189,7 @@ namespace spades {
 						uint32_t normal = *(mp++);
 						int z = static_cast<int>(data >> 24);
 						// SPAssert(z < d);
-						SPAssert(z >= 0);
+						SPAssume(z >= 0);
 
 						auto vv = v2 + tAxis3 * zvals[z];
 						if (vv.z < zNear)
diff --git a/Sources/Draw/SWRenderer.cpp b/Sources/Draw/SWRenderer.cpp
index 19968db00..bc4be8dff 100644
--- a/Sources/Draw/SWRenderer.cpp
+++ b/Sources/Draw/SWRenderer.cpp
@@ -242,10 +242,10 @@ namespace spades {
 			int maxY = light.maxY;
 			int lightHeight = maxY - minY;
 
-			SPAssert(minX >= 0);
-			SPAssert(minY >= 0);
-			SPAssert(maxX <= fw);
-			SPAssert(maxY <= fh);
+			SPAssume(minX >= 0);
+			SPAssume(minY >= 0);
+			SPAssume(maxX <= fw);
+			SPAssume(maxY <= fh);
 
 			Vector3 lightCenter;
 			Vector3 diff = light.param.origin - sceneDef.viewOrigin;
diff --git a/Sources/Draw/SWUtils.h b/Sources/Draw/SWUtils.h
index 966ec839a..c90e3dc7d 100644
--- a/Sources/Draw/SWUtils.h
+++ b/Sources/Draw/SWUtils.h
@@ -32,7 +32,7 @@ namespace spades {
 		int GetNumSWRendererThreads();
 
 		template <class F> static void InvokeParallel(F f, unsigned int numThreads) {
-			SPAssert(numThreads <= 32);
+			SPAssume(numThreads <= 32);
 			std::array<std::unique_ptr<ConcurrentDispatch>, 32> disp;
 			for (auto i = 1U; i < numThreads; i++) {
 				auto ff = [i, &f]() { f(i); };