Only include arm_sve.h in SVE dedicated c source files.

CMakeLists.txt

@@ -941,6 +941,10 @@ if(SDL_ASSEMBLY)
           return 0;
         }]==] COMPILER_SUPPORTS_ARMSVE2)
       if(COMPILER_SUPPORTS_ARMSVE2)
+        # IMPORTANT: As not all AArch64 processors support SVE2, we only
+        #            attach the following compilation options SVE dedicated
+        #            source files.
+        set(SVE2_MARCH_FLAG "-march=armv8-a+sve2")
         set(HAVE_ARMSVE2 TRUE)
       endif()
     cmake_pop_check_state()
@@ -954,6 +958,7 @@ if(SDL_ASSEMBLY)
         "${SDL3_SOURCE_DIR}/src/video/arm/SDL_sve2_blit_A.c"
         "${SDL3_SOURCE_DIR}/src/video/arm/SDL_sve2_blit_N.c"
         PROPERTIES
+          COMPILE_FLAGS "${SVE2_MARCH_FLAG}"
           SKIP_PRECOMPILE_HEADERS ON
       )
     endif()

include/SDL3/SDL_intrin.h

@@ -88,8 +88,7 @@
 /**
  * Defined if (and only if) the compiler supports ARM SVE2 intrinsics.
  *
- * If this macro is defined, SDL will have already included `<arm_sve.h>` as
- * appropriate.
+ * Even if this macro is defined, SDL will NOT included `<arm_sve.h>` globally.
  *
  * \since This macro is available since SDL 3.6.0.
  */
@@ -284,8 +283,8 @@ _m_prefetch(void *__P)
 /* Visual Studio doesn't define __ARM_ARCH, but _M_ARM (if set, always 7), and _M_ARM64 (if set, always 1). */
 #    if defined (_M_ARM64) && 0 /* Please only remove this 0 when MSVC releasing support for SVE2 officially. */
 #      define SDL_SVE2_INTRINSICS 1
-#      include <arm_sve.h>
 #      define __ARM_FEATURE_SVE2 1 /* Set __ARM_FEATURE_SVE2 so that it can be used elsewhere, at compile time */
+#      define __ARM_FEATURE_SVE 1 /* Set __ARM_FEATURE_SVE so that it can be used elsewhere, at compile time */
 #      define __ARM_ARCH 8
 #    endif
 #  elif defined(SDL_PLATFORM_APPLE)
@@ -293,7 +292,12 @@ _m_prefetch(void *__P)
 #  elif defined(__ARM_ARCH) && (__ARM_ARCH >= 8) && (defined(__aarch64__) || defined(_M_ARM64)) && \
         defined(__has_include) && __has_include(<arm_sve.h>)
 #    define SDL_SVE2_INTRINSICS 1
-#    include <arm_sve.h>
+/*
+ * IMPORTANT: Please do NOT put #include <arm_sve.h> here. Some versions of LLVM compilers provide arm_sve.h that 
+ *            raise error when failling in checking the existance of __ARM_FEATURE_SVE, while others are not. To
+ *            improve the portability, we only include arm_sve.h in the source files that are dedicated to SVE 
+ *            accelerations. 
+ */
 #  endif
 #endif
 #endif /* compiler version */

src/video/arm/SDL_sve2_extension.h

@@ -19,10 +19,33 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
+/*
+ * IMPORTANT: Please do NOT include this header file directly or indirectly
+ *            outside the src/video/arm folder.
+ * 
+ */
+
 #if !defined(SDL_SVE2_EXTENSION_H) //&& (defined(__ARM_FEATURE_SVE2) && __ARM_FEATURE_SVE2)
 #define SDL_SVE2_EXTENSION_H
 
 #include "SDL_sve2_util.h"
+
+/*
+ * NOTE: Some Android builds didn't attach '-march=armv8-a+sve2' to 
+ *       SDL_sve2_*.c and hence the macro __ARM_FEATURE_SVE is not
+ *       defined by the compiler. This might not be a problem as the 
+ *       SDL_TARGETING("arch=armv8-a+sve2") enables the feature for
+ *       individual functions, until some version of compilers
+ *       provides arm_sve.h raising errors then __ARM_FEATURE_SVE 
+ *       is not defined. Although it should be avoided, as a 
+ *       workaround, we have to define the __ARM_FEATURE_SVE here as 
+ *       an ugly hack. 
+ */
+#if defined(SDL_PLATFORM_ANDROID) && SDL_PLATFORM_ANDROID
+#ifndef __ARM_FEATURE_SVE
+#define __ARM_FEATURE_SVE 1
+#endif
+#endif
 #include <arm_sve.h>
 #include <stdint.h>
 

src/video/arm/SDL_sve2_swizzle.h

@@ -19,6 +19,12 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
+/*
+ * IMPORTANT: Please do NOT include this header file directly or indirectly
+ *            outside the src/video/arm folder.
+ * 
+ */
+
 #if !defined(SD_SVE2_SWIZZLE_H) //&& (defined(__ARM_FEATURE_SVE2) && __ARM_FEATURE_SVE2)
 #define SD_SVE2_SWIZZLE_H