[libpng16] Cleaned up ARM NEON compilation handling. The tests are now in

pngpriv.h and detect the broken GCC compilers.

ANNOUNCE

@@ -1,5 +1,5 @@
 
-Libpng 1.6.7beta03 - October 17, 2013
+Libpng 1.6.7beta03 - October 18, 2013
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -72,12 +72,14 @@ Version 1.6.7beta02 [October 12, 2013]
   Make autogen.sh work with automake 1.13 as well as 1.14. Do this by always
     removing the 1.14 'compile' script but never checking for it.
 
-Version 1.6.7beta03 [October 17, 2013]
+Version 1.6.7beta03 [October 18, 2013]
   Added ARMv8 support (James Yu <james.yu at linaro.org>).  Added file
     arm/filter_neon_intrinsics.c; enable with configuration flag
     PNG_ARM_NEON_INTRINSICS.
   Revised pngvalid to generate size images with as many filters as it can
     manage, limited by the number of rows.
+  Cleaned up ARM NEON compilation handling. The tests are now in pngpriv.h
+    and detect the broken GCC compilers.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

CHANGES

@@ -4686,12 +4686,14 @@ Version 1.6.7beta02 [October 12, 2013]
   Make autogen.sh work with automake 1.13 as well as 1.14. Do this by always
     removing the 1.14 'compile' script but never checking for it.
 
-Version 1.6.7beta03 [October 17, 2013]
+Version 1.6.7beta03 [October 18, 2013]
   Added ARMv8 support (James Yu <james.yu at linaro.org>).  Added file
     arm/filter_neon_intrinsics.c; enable with configuration flag
     PNG_ARM_NEON_INTRINSICS.
   Revised pngvalid to generate size images with as many filters as it can
     manage, limited by the number of rows.
+  Cleaned up ARM NEON compilation handling. The tests are now in pngpriv.h
+    and detect the broken GCC compilers.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

arm/filter_neon.S

@@ -22,9 +22,10 @@
 
 /* Assembler NEON support - only works for 32-bit ARM (i.e. it does not work for
  * ARM64).  The code in arm/filter_neon_intrinsics.c supports ARM64, however it
- * only works if -mfpu=neon is specified on the GCC command line.
+ * only works if -mfpu=neon is specified on the GCC command line.  See pngpriv.h
+ * for the logic which sets PNG_USE_ARM_NEON_ASM:
  */
-#ifndef __ARM_NEON__ /* else use arm/filter_neon_intrinsics.c */
+#ifdef PNG_USE_ARM_NEON_ASM /* else use arm/filter_neon_intrinsics.c */
 
 #ifdef PNG_READ_SUPPORTED
 #if PNG_ARM_NEON_OPT > 0
@@ -241,4 +242,4 @@ func    png_read_filter_row_paeth3_neon, export=1
 endfunc
 #endif /* PNG_ARM_NEON_OPT > 0 */
 #endif /* PNG_READ_SUPPORTED */
-#endif /* !__ARM_NEON__ */
+#endif /* PNG_USE_ARM_NEON_ASM */

arm/filter_neon_intrinsics.c

@@ -15,7 +15,7 @@
 #include "pngpriv.h"
 
 /* This code requires -mfpu=neon on the command line: */
-#ifdef __ARM_NEON__ /* else use arm/filter_neon.S */
+#ifndef PNG_USE_ARM_NEON_ASM /* else use arm/filter_neon.S */
 
 #include <arm_neon.h>
 
@@ -369,4 +369,4 @@ png_read_filter_row_paeth4_neon(png_row_infop row_info, png_bytep row,
 
 #endif /* PNG_ARM_NEON_OPT > 0 */
 #endif /* PNG_READ_SUPPORTED */
-#endif /* __ARM_NEON__ */
+#endif /* !PNG_USE_ARM_NEON_ASM */

pngpriv.h

@@ -128,6 +128,30 @@
 #  define PNG_FILTER_OPTIMIZATIONS png_init_filter_functions_neon
 #endif
 
+#ifndef PNG_USE_ARM_NEON_ASM
+   /* By default the 'intrinsics' code in arm/filter_neon_intrinsics.c is used
+    * if possible - if __ARM_NEON__ is set and the compiler version is not known
+    * to be broken.  ASM code can be forced by -DPNG_USE_ARM_NEON_ASM on the
+    * command line.
+    */
+#  ifndef __ARM_NEON__
+      /* The 'intrinsics' code simply won't compile without this -mfpu=neon: */
+#     define PNG_USE_ARM_NEON_ASM
+#  endif
+#endif
+
+   /* Put compiler specific checks below: */
+#ifndef PNG_USE_ARM_NEON_ASM
+#  ifdef __GNUC__
+      /* GCC 4.5.4 NEON support is known to be broken.  4.6.3 is known to work,
+       * so if this *is* GCC, or G++, look for a version >4.5
+       */
+#     if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 6)
+#        define PNG_USE_ARM_NEON_ASM
+#     endif
+#  endif
+#endif
+
 /* Is this a build of a DLL where compilation of the object modules requires
  * different preprocessor settings to those required for a simple library?  If
  * so PNG_BUILD_DLL must be set.