[libpng17] Attempt to fix the arm-neon configuration mess.

ANNOUNCE

@@ -263,6 +263,7 @@ Version 1.7.0beta09 [April 24, 2013]
     was switched 'off' as opposed to being explicitly disabled.
 
 Version 1.7.0beta10 [April 24, 2013]
+  Attempt to fix the PNG_ARM_NEON mess.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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CHANGES

@@ -4551,6 +4551,7 @@ Version 1.7.0beta09 [April 24, 2013]
     was switched 'off' as opposed to being explicitly disabled.
 
 Version 1.7.0beta10 [April 24, 2013]
+  Attempt to fix the PNG_ARM_NEON mess.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

arm/arm_init.c

@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2013 Glenn Randers-Pehrson
  * Written by Mans Rullgard, 2011.
- * Last changed in libpng 1.5.15 [March 28, 2013]
+ * Last changed in libpng 1.7.0 [(PENDING RELEASE)]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -216,4 +216,4 @@ png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
           png_read_filter_row_paeth4_neon;
    }
 }
-#endif /* FILTER_OPTIMIZATIONS && __arm__ && __ARM_NEON__ */
+#endif /* PNG_ARM_NEON_SUPPORTED */

arm/filter_neon.S

@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2013 Glenn Randers-Pehrson
  * Written by Mans Rullgard, 2011.
- * Last changed in libpng 1.6.2 [(PENDING RELEASE)]
+ * Last changed in libpng 1.7.0 [(PENDING RELEASE)]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -11,7 +11,7 @@
  */
 
 /* This is required to get the symbol renames, which are #defines, and also
- * includes the value of PNG_FILTER_OPTIMIZATIONS.
+ * includes the definition (or not) of PNG_ARM_NEON_SUPPORTED.
  */
 #define PNG_VERSION_INFO_ONLY
 #include "../pngpriv.h"
@@ -20,8 +20,7 @@
 .section .note.GNU-stack,"",%progbits /* mark stack as non-executable */
 #endif
 
-#if defined(PNG_FILTER_OPTIMIZATIONS) && defined(__arm__) && \
+#ifdef PNG_ARM_NEON_SUPPORTED
-   defined(__ARM_NEON__)
 
 #ifdef __ELF__
 #   define ELF
@@ -233,4 +232,4 @@ func    png_read_filter_row_paeth3_neon, export=1
 
         pop             {r4,pc}
 endfunc
-#endif /* FILTER_OPTIMIZATIONS && __arm__ && __ARM_NEON__ */
+#endif /* PNG_ARM_NEON_SUPPORTED */

configure.ac

@@ -334,19 +334,26 @@ AC_ARG_WITH(libpng-prefix,
     fi])
 AM_CONDITIONAL([DO_PNG_PREFIX], [test "${with_libpng_prefix:-no}" != "no"])
 
+# HOST SPECIFIC OPTIONS
+# =====================
+#
+# ARM
+# ===
+#
+# ARM NEON (SIMD) support.
+
 AC_ARG_ENABLE([arm-neon],
    AS_HELP_STRING([[[--enable-arm-neon]]],
-      [Enable ARM NEON optimizations: =off, check, api, on:]
+      [Enable ARM NEON optimizations: =no/off, check, api, yes/on:]
-      [off: disable the optimizations; check: use internal checking code]
+      [no/off: disable the optimizations; check: use internal checking code]
       [(deprecated and poorly supported); api: disable by default, enable by]
-      [a call to png_set_option; on: turn on unconditionally.  The]
+      [a call to png_set_option; yes/on: turn on unconditionally.]),
-      [default is 'on' if __ARM_NEON__ is defined, otherwise 'off'.]),
    [case "$enableval" in
       no|off)
          # disable the default enabling on __ARM_NEON__ systems:
          AC_DEFINE([PNG_NO_ARM_NEON], [],
                    [Disable ARM Neon optimizations])
-         # Prevent use of the assembler files below:
+         # Prevent inclusion of the assembler files below:
          enable_arm_neon=no;;
       check)
          AC_DEFINE([PNG_ARM_NEON_CHECK_SUPPORTED], [],
@@ -354,13 +361,21 @@ AC_ARG_ENABLE([arm-neon],
       api)
          AC_DEFINE([PNG_ARM_NEON_API_SUPPORTED], [],
                    [Turn on ARM Neon optimizations at run-time]);;
-      on)
+      yes|on)
          AC_DEFINE([PNG_ARM_NEON_SUPPORTED], [],
                    [Enable ARM Neon optimizations]);;
       *)
-         AC_MSG_ERROR([arm-neon: option value required (off/check/api/on)]);;
+         AC_MSG_ERROR([--enable-arm-neon=${enable_arm_neon}: invalid value])
    esac])
-AM_CONDITIONAL([PNG_ARM_NEON], [test "${enable_arm_neon:-no}" != "no"])
+
+# If enable/disable was not specified default to using the optimizations if the
+# host CPU is ARM and the comppiler is targeting a NEON host.  The latter test
+# is done in scripts/pnglibconf.dfa by checking for __ARM_NEON__.  The
+# AM_CONDITIONAL below controls whether the ARM NEON source files are built.
+
+AM_CONDITIONAL([PNG_ARM_NEON],
+   [test "$enable_arm_neon" != 'no' &&
+    test "$host_cpu" = 'arm' -o "$enable_arm_neon" != ''])
 
 AC_MSG_NOTICE([[Extra options for compiler: $PNG_COPTS]])