Merge pull request tesseract-ocr#3061 from stweil/neon

Always use NEON by default for ARMv8

Makefile.am

@@ -184,7 +184,7 @@ noinst_LTLIBRARIES += libtesseract_sse.la
 endif
 
 if HAVE_NEON
-libtesseract_neon_la_CXXFLAGS = -mfpu=neon
+libtesseract_neon_la_CXXFLAGS = $(NEON_CXXFLAGS)
 libtesseract_neon_la_SOURCES = src/arch/intsimdmatrixneon.cpp
 libtesseract_la_LIBADD += libtesseract_neon.la
 noinst_LTLIBRARIES += libtesseract_neon.la

configure.ac

@@ -160,12 +160,21 @@ case "${host_cpu}" in
 
     ;;
 
+  aarch64)
+
+    # ARMv8 always has NEON and does not need special compiler flags.
+    AM_CONDITIONAL([HAVE_NEON], true)
+    AC_DEFINE([HAVE_NEON], [1], [Enable NEON instructions])
+    ;;
+
   arm*)
 
     AX_CHECK_COMPILE_FLAG([-mfpu=neon], [neon=true], [neon=false], [$WERROR])
     AM_CONDITIONAL([HAVE_NEON], $neon)
     if $neon; then
       AC_DEFINE([HAVE_NEON], [1], [Enable NEON instructions])
+      NEON_CXXFLAGS="-mfpu=neon"
+      AC_SUBST([NEON_CXXFLAGS])
     fi
 
     ;;

src/arch/simddetect.cpp

@@ -37,7 +37,7 @@
 #endif
 #endif
 
-#ifdef HAVE_NEON
+#if defined(HAVE_NEON) && !defined(__aarch64__)
 #ifdef ANDROID
 #include <cpufeatures.h>
 #else
@@ -66,7 +66,10 @@ static STRING_VAR(dotproduct, "auto",
 
 SIMDDetect SIMDDetect::detector;
 
-#if defined(HAVE_NEON)
+#if defined(__aarch64__)
+// ARMv8 always has NEON.
+bool SIMDDetect::neon_available_ = true;
+#elif defined(HAVE_NEON)
 // If true, then Neon has been detected.
 bool SIMDDetect::neon_available_;
 #else
@@ -177,7 +180,7 @@ SIMDDetect::SIMDDetect() {
 #endif
 #endif
 
-#ifdef HAVE_NEON
+#if defined(HAVE_NEON) && !defined(__aarch64__)
 #ifdef ANDROID
   {
     AndroidCpuFamily family = android_getCpuFamily();