[libpng16] Removed PNG_FILTER_OPTIMIZATIONS and PNG_ARM_NEON_SUPPORTED from

pnglibconf.h, allowing more of the decisions to be made internally
(pngpriv.h) during the compile.  Without this, symbol prefixing is broken
under certain circumstances on ARM platforms.  Now only the API parts of
the optimizations ('check' vs 'api') are exposed in the public header files
except that the new setting PNG_ARM_NEON_OPT documents how libpng makes the
decision about whether or not to use the optimizations.

ANNOUNCE

 
-Libpng 1.6.3beta07 - June 6, 2013
+Libpng 1.6.3beta07 - June 8, 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.
@@ -77,7 +77,7 @@ Version 1.6.3beta06 [May 12, 2013]
     right zlib header files.
   Separated CPPFLAGS and CFLAGS in contrib/pngminim/*/makefile
 
-Version 1.6.3beta07 [June 6, 2013]
+Version 1.6.3beta07 [June 8, 2013]
   Removed a redundant test in png_set_IHDR().
   Added set(CMAKE_CONFIGURATION_TYPES ...) to CMakeLists.txt (Andrew Hundt)
   Deleted set(CMAKE_BUILD_TYPE) block from CMakeLists.txt
@@ -86,6 +86,13 @@ Version 1.6.3beta07 [June 6, 2013]
   Make ARM NEON support work at compile time (not just configure time).
     This moves the test on __ARM_NEON__ into pngconf.h to avoid issues when
     using a compiler that compiles for multiple architectures at one time.
+  Removed PNG_FILTER_OPTIMIZATIONS and PNG_ARM_NEON_SUPPORTED from
+    pnglibconf.h, allowing more of the decisions to be made internally
+    (pngpriv.h) during the compile.  Without this, symbol prefixing is broken
+    under certain circumstances on ARM platforms.  Now only the API parts of
+    the optimizations ('check' vs 'api') are exposed in the public header files
+    except that the new setting PNG_ARM_NEON_OPT documents how libpng makes the
+    decision about whether or not to use the optimizations.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

CHANGES

@@ -4561,7 +4561,7 @@ Version 1.6.3beta06 [May 12, 2013]
     right zlib header files.
   Separated CPPFLAGS and CFLAGS in contrib/pngminim/*/makefile
 
-Version 1.6.3beta07 [June 6, 2013]
+Version 1.6.3beta07 [June 8, 2013]
   Removed a redundant test in png_set_IHDR().
   Added set(CMAKE_CONFIGURATION_TYPES ...) to CMakeLists.txt (Andrew Hundt)
   Deleted set(CMAKE_BUILD_TYPE) block from CMakeLists.txt
@@ -4570,6 +4570,13 @@ Version 1.6.3beta07 [June 6, 2013]
   Make ARM NEON support work at compile time (not just configure time).
     This moves the test on __ARM_NEON__ into pngconf.h to avoid issues when
     using a compiler that compiles for multiple architectures at one time.
+  Removed PNG_FILTER_OPTIMIZATIONS and PNG_ARM_NEON_SUPPORTED from
+    pnglibconf.h, allowing more of the decisions to be made internally
+    (pngpriv.h) during the compile.  Without this, symbol prefixing is broken
+    under certain circumstances on ARM platforms.  Now only the API parts of
+    the optimizations ('check' vs 'api') are exposed in the public header files
+    except that the new setting PNG_ARM_NEON_OPT documents how libpng makes the
+    decision about whether or not to use the optimizations.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

arm/arm_init.c

@@ -16,7 +16,7 @@
 
 #include "../pngpriv.h"
 
-#ifdef PNG_ARM_NEON_SUPPORTED
+#if PNG_ARM_NEON_OPT > 0
 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED /* Do run-time checks */
 #include <signal.h> /* for sig_atomic_t */
 
@@ -216,4 +216,4 @@ png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
           png_read_filter_row_paeth4_neon;
    }
 }
-#endif /* PNG_ARM_NEON_SUPPORTED */
+#endif /* PNG_ARM_NEON_OPT > 0 */

arm/filter_neon.S

@@ -11,7 +11,7 @@
  */
 
 /* This is required to get the symbol renames, which are #defines, and also
- * includes the definition (or not) of PNG_ARM_NEON_SUPPORTED.
+ * includes the definition (or not) of PNG_ARM_NEON_OPT.
  */
 #define PNG_VERSION_INFO_ONLY
 #include "../pngpriv.h"
@@ -20,7 +20,7 @@
 .section .note.GNU-stack,"",%progbits /* mark stack as non-executable */
 #endif
 
-#ifdef PNG_ARM_NEON_SUPPORTED
+#if PNG_ARM_NEON_OPT > 0
 
 #ifdef __ELF__
 #   define ELF
@@ -232,4 +232,4 @@ func    png_read_filter_row_paeth3_neon, export=1
 
         pop             {r4,pc}
 endfunc
-#endif /* PNG_ARM_NEON_SUPPORTED */
+#endif /* PNG_ARM_NEON_OPT > 0 */

configure.ac

@@ -244,7 +244,7 @@ AC_ARG_ENABLE([arm-neon],
    [case "$enableval" in
       no|off)
          # disable the default enabling on __ARM_NEON__ systems:
-         AC_DEFINE([PNG_ARM_NEON_NOT_SUPPORTED], [],
+         AC_DEFINE([PNG_ARM_NEON_OPT], [0],
                    [Disable ARM Neon optimizations])
          # Prevent inclusion of the assembler files below:
          enable_arm_neon=no;;
@@ -255,8 +255,11 @@ AC_ARG_ENABLE([arm-neon],
          AC_DEFINE([PNG_ARM_NEON_API_SUPPORTED], [],
                    [Turn on ARM Neon optimizations at run-time]);;
       yes|on)
-         AC_DEFINE([PNG_ARM_NEON_SUPPORTED], [],
-                   [Enable ARM Neon optimizations]);;
+         AC_DEFINE([PNG_ARM_NEON_OPT], [2],
+                   [Enable ARM Neon optimizations])
+         AC_MSG_WARN([--enable-arm-neon: please specify 'check' or 'api', if]
+            [you want the optimizations unconditionally pass -mfpu=neon]
+            [to the compiler.]);;
       *)
          AC_MSG_ERROR([--enable-arm-neon=${enable_arm_neon}: invalid value])
    esac])

pngconf.h

 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.6.3beta07 - June 6, 2013
+ * libpng version 1.6.3beta07 - June 8, 2013
  *
  * Copyright (c) 1998-2013 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -194,30 +194,6 @@
  *                PNG_USE_DLL is set.
  */
 
-/* Compile time options.
- * =====================
- * In a multi-arch build the compiler may compile the code several times for the
- * same object module, producing different codes for different architectures.
- * When this happens configure-time setting of the target host options cannot be
- * done and this interferes with the handling of the ARM NEON optimizations, and
- * possibly other similiar optimizations.  Put additional tests here; in general
- * this is needed when the same option can be changed at both compile time and
- * run time depending on the target OS (i.e. iOS vs Android.)
- */
-#ifdef __ARM_NEON__
-   /* If the default below causes problems set PNG_ARM_NEON_NOT_SUPPORTED either
-    * by passing --enable-arm-neon=no to configure or setting it in some other
-    * way when pnglibconf.h is built.
-    */
-#  if (!defined PNG_ARM_NEON_SUPPORTED) && (!defined PNG_ARM_NEON_NOT_SUPPORTED)
-#     define PNG_ARM_NEON_SUPPORTED
-#  endif
-#endif
-
-#if (defined PNG_ARM_NEON_SUPPORTED) && (defined PNG_ARM_NEON_NOT_SUPPORTED)
-#  error configuration: ARM_NEON cannot both be supported and disabled
-#endif
-
 /* System specific discovery.
  * ==========================
  * This code is used at build time to find PNG_IMPEXP, the API settings
@@ -262,6 +238,7 @@
 #      define PNGAPI _stdcall
 #    endif
 #  endif /* compiler/api */
+
   /* NOTE: PNGCBAPI always defaults to PNGCAPI. */
 
 #  if defined(PNGAPI) && !defined(PNG_USER_PRIVATEBUILD)

pngpriv.h

@@ -88,6 +88,38 @@
 #  endif
 #endif
 
+/* Compile time options.
+ * =====================
+ * In a multi-arch build the compiler may compile the code several times for the
+ * same object module, producing different binaries for different architectures.
+ * When this happens configure-time setting of the target host options cannot be
+ * done and this interferes with the handling of the ARM NEON optimizations, and
+ * possibly other similiar optimizations.  Put additional tests here; in general
+ * this is needed when the same option can be changed at both compile time and
+ * run time depending on the target OS (i.e. iOS vs Android.)  The changes have
+ * to occur here to get the symbol prefixing to work consistently.
+ */
+#ifndef PNG_ARM_NEON_OPT
+   /* ARM NEON optimizations are being controlled by the compiler settings,
+    * typically the target FPU.  If the FPU has been set to NEON (-mfpu=neon
+    * with GCC) then the compiler will define __ARM_NEON__ and we can rely
+    * unconditionally on NEON instructions not crashing, otherwise we must
+    * disable use of NEON instructions:
+    */
+#  ifdef __ARM_NEON__
+#     define PNG_ARM_NEON_OPT 2
+#  else
+#     define PNG_ARM_NEON_OPT 0
+#  endif
+#endif
+
+#if PNG_ARM_NEON_OPT > 0
+   /* NEON optimizations are to be at least considered by libpng, enable the
+    * callbacks to do this.  (This is what matters for the symbol prefixing.)
+    */
+#  define PNG_FILTER_OPTIMIZATIONS png_init_filter_functions_neon
+#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.

scripts/pnglibconf.dfa

@@ -193,31 +193,38 @@ setting PREFIX
 
 setting DEFAULT_READ_MACROS default 1
 
-# This setting allows a hardware or configuration specific filter optimization
-# function to be specified, the argument is the name of the filter initializaion
-# function to use.
-
-setting FILTER_OPTIMIZATIONS
-
 # Implementation specific control of the optimizations, enabled by those
 # hardware or software options that need it (typically when run-time choices
 # must be made by the user)
 option SET_OPTION disabled
 
-# These options are specific to the ARM NEON hardware optimizations:
-#
-# ARM_NEON: the optimization itself
-# ARM_NEON_NOT: disable the optimization even on systems that apparently support
-#               it (where the compiler defines __ARM_NEON__).
-# ARM_NEON_API: allow the optimization to be switched on with png_set_hardware
-# ARM_NEON_CHECK: compile a run-time check to see if Neon extensions are
-#                 supported, this is poorly supported and deprectated - use the
-#                 png_set_hardware API.
-option ARM_NEON disabled,
-   sets FILTER_OPTIMIZATIONS png_init_filter_functions_neon
-option ARM_NEON_NOT disabled
-option ARM_NEON_API disabled enables SET_OPTION ARM_NEON
-option ARM_NEON_CHECK disabled enables ARM_NEON
+# These options are specific to the ARM NEON hardware optimizations.  At present
+# these optimizations depend on GCC specific pre-processing of an assembler (.S)
+# file so they probably won't work with other compilers.
+#
+# ARM_NEON_OPT: unset: check at compile time (__ARM_NEON__ must be defined by
+#                      the compiler, typically as a result of specifying
+#                      -mfpu=neon on the command line.)
+#                   0: disable (even if the CPU has a NEON FPU.)
+#                   1: check at run time (via ARM_NEON_{API,CHECK})
+#                   2: switch on unconditionally (inadvisable - instead pass
+#                      -mfpu=neon to GCC in CFLAGS)
+#           When building libpng avoid using any setting other than '0'; '1' is
+#           set automatically when either 'API' or 'CHECK' are configured in,
+#           '2' should not be necessary as -mfpu=neon will achieve the same
+#           effect as well as applying NEON optimizations to the rest of the
+#           libpng code.
+#           NOTE: any setting other than '0' requires ALIGNED_MEMORY
+# ARM_NEON_API:   (PNG_ARM_NEON == 1) allow the optimization to be switched on
+#                 with png_set_option
+# ARM_NEON_CHECK: (PNG_ARM_NEON == 1) compile a run-time check to see if Neon
+#                 extensions are supported, this is poorly supported and
+#                 deprectated - use the png_set_option API.
+setting ARM_NEON_OPT
+option ARM_NEON_API disabled requires ALIGNED_MEMORY enables SET_OPTION,
+   sets ARM_NEON_OPT 1
+option ARM_NEON_CHECK disabled requires ALIGNED_MEMORY,
+   sets ARM_NEON_OPT 1
 
 # These settings configure the default compression level (0-9) and 'strategy';
 # strategy is as defined by the implementors of zlib, it describes the input

scripts/pnglibconf.h.prebuilt

@@ -2,7 +2,7 @@
 
 /* pnglibconf.h - library build configuration */
 
-/* Libpng version 1.6.3beta07 - May 12, 2013 */
+/* Libpng version 1.6.3beta07 - June 8, 2013 */
 
 /* Copyright (c) 1998-2013 Glenn Randers-Pehrson */
 
@@ -20,7 +20,6 @@
 #define PNG_ALIGNED_MEMORY_SUPPORTED
 /*#undef PNG_ARM_NEON_API_SUPPORTED*/
 /*#undef PNG_ARM_NEON_CHECK_SUPPORTED*/
-/*#undef PNG_ARM_NEON_SUPPORTED*/
 #define PNG_BENIGN_ERRORS_SUPPORTED
 #define PNG_BENIGN_READ_ERRORS_SUPPORTED
 /*#undef PNG_BENIGN_WRITE_ERRORS_SUPPORTED*/