Added Raspberry Pi cross-compilation support to makefile

tensorflow/contrib/makefile/.gitignore

@@ -0,0 +1,2 @@
+gen/
+downloads/

tensorflow/contrib/makefile/Makefile

@@ -95,7 +95,7 @@ PROTOGENDIR := $(GENDIR)proto/
 # Settings for the target compiler.
 CXX := gcc
 OPTFLAGS := -O0
-CXXFLAGS := --std=c++11
+CXXFLAGS := --std=c++11 $(OPTFLAGS)
 LDFLAGS := \
 -L/usr/local/lib
 INCLUDES := \
@@ -127,6 +127,13 @@ endif
 ifeq ($(TARGET),LINUX)
 	LIBS += -ldl
 endif
+# If we're cross-compiling for the Raspberry Pi, use the right gcc.
+ifeq ($(TARGET),PI)
+	CXX := arm-linux-gnueabihf-g++
+	LDFLAGS := -L$(GENDIR)protobuf_pi/lib/ -Wl,--no-whole-archive
+	LIBS += -ldl
+	LIBFLAGS += -Wl,--allow-multiple-definition -Wl,--whole-archive
+endif
 
 # Set up Android building
 ifeq ($(TARGET),ANDROID)

tensorflow/contrib/makefile/README.md

@@ -130,6 +130,27 @@ to register ops and kernels.
 The example Xcode project in tensorflow/contrib/ios_example shows how to use the
 static library in a simple app.
 
+## Raspberry Pi
+
+The easiest way to build for the Raspberry Pi is to cross-compile from Linux.
+To use this makefile to do that, you first need to install the right version of
+the compiler to target the Pi, using a command like this on your Linux machine:
+
+```bash
+sudo apt-get install g++-arm-linux-gnueabihf
+```
+
+After that, run `tensorflow/contrib/makefile/compile_pi_protobuf.sh` to build a
+version of the protobuf library aimed at the Pi. Then you should be able to run:
+
+```bash
+make -f tensorflow/contrib/makefile/Makefile TARGET=PI
+```
+
+This will build the static library, and the example benchmark executable. You
+can then copy the `tensorflow/contrib/makefile/gen/bin/benchmark` program over
+to your Raspberry Pi, and run it there.
+
 ## Dependencies
 
 The Makefile loads in a list of dependencies stored in text files. These files

tensorflow/contrib/makefile/compile_pi_protobuf.sh

@@ -0,0 +1,33 @@
+#!/bin/bash -x
+# Builds protobuf 3 for iOS.
+
+cd tensorflow/contrib/makefile
+
+GENDIR=`pwd`/gen/protobuf_pi/
+LIBDIR=${GENDIR}
+mkdir -p ${LIBDIR}
+
+CXX=arm-linux-gnueabihf-g++
+
+cd downloads/protobuf
+
+./autogen.sh
+if [ $? -ne 0 ]
+then
+  echo "./autogen.sh command failed."
+  exit 1
+fi
+
+make distclean
+./configure \
+--build=i686-pc-linux-gnu \
+--host=arm-linux \
+--target=arm-linux \
+--disable-shared \
+--enable-cross-compile \
+--with-protoc=protoc \
+--prefix=${LIBDIR} \
+--exec-prefix=${LIBDIR} \
+"CXX=${CXX}" \
+make
+make install