Issue 'yield' in main loop to give CPU time to cool down.

This is functional equvalent to the 'pause' instruction on x86.

CMakeLists.txt

@@ -165,6 +165,14 @@ if ("${ARCH}" STREQUAL "x86_64")
 	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mfpmath=sse")
 endif()
 
+if ("${ARCH}" STREQUAL "arm")
+    if (CMAKE_SIZEOF_VOID_P EQUAL 4)
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -march=armv6k")
+    else()
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -march=armv8.0-a")
+    endif()
+endif()
+
 set(Backends-Generic-Source
 	${BACKENDS_SRC_DIR}/generic/misc.c
 	)

Makefile

@@ -186,6 +186,16 @@ ifeq ($(YQ2_ARCH), x86_64)
 CFLAGS += -mfpmath=sse
 endif
 
+# In ARM mode it cannot generate yield instruction
+# to cool down the CPU in busy mode
+ifeq ($(YQ2_ARCH), arm)
+CFLAGS += -march=armv6k
+endif
+
+ifeq ($(YQ2_ARCH), aarch64)
+CFLAGS += -march=armv8.0-a
+endif
+
 # ----------
 
 # Systemwide installation.

src/common/frame.c

@@ -139,13 +139,15 @@ Qcommon_Mainloop(void)
 
 			while (1)
 			{
-#if defined (__GNUC__) && (__i386 || __x86_64__)
 				/* Give the CPU a hint that this is a very tight
 				   spinloop. One PAUSE instruction each loop is
 				   enough to reduce power consumption and head
 				   dispersion a lot, it's 95°C against 67°C on
 				   a Kaby Lake laptop. */
+#if defined (__GNUC__) && (__i386 || __x86_64__)
 				asm("pause");
+#elif defined(__arm__) || defined(__aarch64__)
+				asm("yield");
 #endif
 
 				if (Sys_Microseconds() - spintime >= FRAMEDELAY)