Lower ARM architecture requirement for CRC32 instructions.

The changes ensure compatibility with compilers targeting ARMv7.
32-bit processors of architecture 8 and higher, or 64-bit processors running in 32-bit mode can have the CRC32 instructions.
With this change we will query the processor instead of the compiler architecture.

crc32.c

@@ -48,7 +48,7 @@ AARU_EXPORT int AARU_CALL crc32_update(crc32_ctx* ctx, const uint8_t* data, uint
 #endif
 
 #if defined(__aarch64__) || defined(_M_ARM64) || defined(__arm__) || defined(_M_ARM)
-#if __ARM_ARCH >= 8
+#if __ARM_ARCH >= 7
     if(have_arm_crc32())
     {
         ctx->crc = armv8_crc32_little(ctx->crc, data, len);

crc32_arm_simd.c

@@ -30,9 +30,9 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#if(defined(__aarch64__) || defined(_M_ARM64) || defined(__arm__) || defined(_M_ARM)) && __ARM_ARCH >= 8
+#if(defined(__aarch64__) || defined(_M_ARM64) || defined(__arm__) || defined(_M_ARM)) && __ARM_ARCH >= 7
 
-#if defined(__MINGW32__) && !defined(__ARM_FEATURE_CRC32)
+#if !defined(__ARM_FEATURE_CRC32)
 #define __ARM_FEATURE_CRC32 1
 #endif
 

simd.c

@@ -198,6 +198,12 @@ int have_arm_crc32(void)
 #elif defined(__APPLE__)
     return have_crc32_apple();
 #else
+
+// Not defined in ARMv7 compilers, even if the CPU has the capability
+#ifndef HWCAP2_CRC32
+#define HWCAP2_CRC32 (1 << 4)
+#endif
+
     return getauxval(AT_HWCAP2) & HWCAP2_CRC32;
 #endif
 }

simd.h

@@ -92,7 +92,7 @@ AARU_EXPORT int have_arm_crypto(void);
 #define TARGET_WITH_SIMD
 #else
 
-#if __ARM_ARCH >= 8
+#if (__ARM_ARCH >= 7 || defined (__ARM_ARCH_8A))
 
 #ifdef __clang__
 #define TARGET_ARMV8_WITH_CRC __attribute__((target("armv8-a,crc")))
@@ -100,7 +100,7 @@ AARU_EXPORT int have_arm_crypto(void);
 #define TARGET_ARMV8_WITH_CRC __attribute__((target("arch=armv8-a+crc")))
 #endif
 
-#endif // __ARM_ARCH >= 8
+#endif // __ARM_ARCH_7A__
 
 #ifdef __clang__
 #define TARGET_WITH_CRYPTO __attribute__((target("armv8-a,crypto")))