Update README.md for showing how to enable SSE2/AVX2

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Takeshi YAMAMURO 2016-04-14 14:02:34 +09:00
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@ -143,6 +143,12 @@ Older snapshots of snappy contain a buggy config.h.in that does not work properl
$ export JAVA_HOME=/usr/lib/jvm/java-1.7.1-ibm-1.7.1.2.10-1jpp.3.el7_0.s390x
$ make USE_GIT=1 GIT_REPO_URL=https://github.com/google/snappy.git GIT_SNAPPY_BRANCH=master IBM_JDK_7=1
## Activating SSE2/AVX2 instructions in BitShuffle
The most of the native libraries that snappy-java contains disable SSE2/AVX2 instructions in terms of portability (SSE2 is enabled only in Linux/x86_64 platforms). To enable AVX2 instructions, you need to compile as follows:
$ make CXXFLAGS_BITSHUFFLE=-mavx2 # -msse2 for SSE2 instructions
## Cross-compiling for other platforms
The Makefile contains rules for cross-compiling the native library for other platforms so that the snappy-java JAR can support multiple platforms. For example, to build the native libraries for x86 Linux, x86 and x86-64 Windows, and soft- and hard-float ARM: