+XIV. Enabling or disabling hardware optimizations
+
+Certain hardware capabilities, such as the Intel SSE instructions,
+are normally detected at run time. Enable them with configure options
+such as one of
+
+ --enable-arm-neon=yes
+ --enable-mips-msa=yes
+ --enable-intel-sse=yes
+ --enable-powerpc-vsx=yes
+
+or enable them all at once with
+
+ --enable-hardware-optimizations=yes
+
+or, if you are not using "configure", you can use one
+or more of
+
+ CPPFLAGS += "-DPNG_ARM_NEON"
+ CPPFLAGS += "-DPNG_MIPS_MSA"
+ CPPFLAGS += "-DPNG_INTEL_SSE"
+ CPPFLAGS += "-DPNG_POWERPC_VSX"
+
+See for example scripts/makefile.linux-opt
+
+If you wish to avoid using them,
+you can disable them via the configure option
+
+ --disable-hardware-optimizations
+
+to disable them all, or
+
+ --enable-intel-sse=no
+
+to disable a particular one,
+or via compiler-command options such as
+
+ CPPFLAGS += "-DPNG_ARM_NEON_OPT=0, -DPNG_MIPS_MSA_OPT=0,
+ -DPNG_INTEL_SSE_OPT=0, -DPNG_POWERPC_VSX_OPT=0"
+
+If you are using cmake, hardware optimizations are "on"
+by default. To disable them, use
+
+ cmake . -DPNG_ARM_NEON=no -DPNG_INTEL_SSE=no \
+ -DPNG_MIPS_MSA=no -DPNG_POWERPC_VSX=no
+
+or disable them all at once with
+
+ cmake . -DPNG_HARDWARE_OPTIMIZATIONS=no
+
+XV. Changes to the build and configuration of libpng in libpng-1.5.x