eigen: Add install_eigen_headers target for installing to system (tensorflow#20281)

Eigen provides files that are both GPL and MPL. Tensorflow uses only the
MPL headers. This target collects all the headers into genfiles so they
can be easily installed to /usr/include/ later.

Thanks to [email protected] for all the help testing and figuring
out what was missing. And to [email protected] for pointers to the solution.

Signed-off-by: Jason Zaman <[email protected]>

Author: perfinion

third_party/eigen.BUILD

@@ -69,3 +69,9 @@ cc_library(
     includes = ["."],
     visibility = ["//visibility:public"],
 )
+
+filegroup(
+    name = "eigen_header_files",
+    srcs = EIGEN_MPL2_HEADER_FILES,
+    visibility = ["//visibility:public"],
+)

third_party/eigen3/BUILD

@@ -17,21 +17,23 @@ load("//tensorflow:tensorflow.bzl", "if_mkl")
 # INTEL_MKL end
 load("//tensorflow:tensorflow.bzl", "if_mkl")
 
+EIGEN3_THIRD_PARTY_HEADERS = [
+    "Eigen/Core",
+    "Eigen/LU",
+    "Eigen/Cholesky",
+    "Eigen/Eigenvalues",
+    "Eigen/QR",
+    "Eigen/SVD",
+    "unsupported/Eigen/MatrixFunctions",
+    "unsupported/Eigen/SpecialFunctions",
+    "unsupported/Eigen/CXX11/ThreadPool",
+    "unsupported/Eigen/CXX11/Tensor",
+    "unsupported/Eigen/CXX11/FixedPoint",
+] + glob(["unsupported/Eigen/CXX11/src/FixedPoint/*.h"])
+
 cc_library(
     name = "eigen3",
-    hdrs = glob(["unsupported/Eigen/CXX11/src/FixedPoint/*.h"]) + [
-        "Eigen/Core",
-        "Eigen/LU",
-        "Eigen/Cholesky",
-        "Eigen/Eigenvalues",
-        "Eigen/QR",
-        "Eigen/SVD",
-        "unsupported/Eigen/MatrixFunctions",
-        "unsupported/Eigen/SpecialFunctions",
-        "unsupported/Eigen/CXX11/ThreadPool",
-        "unsupported/Eigen/CXX11/Tensor",
-        "unsupported/Eigen/CXX11/FixedPoint",
-    ],
+    hdrs = EIGEN3_THIRD_PARTY_HEADERS,
     includes = if_mkl(["./mkl_include"]),
     visibility = ["//visibility:public"],
     deps = [
@@ -48,3 +50,35 @@ filegroup(
     ),
     visibility = ["//tensorflow:__subpackages__"],
 )
+
+filegroup(
+    name = "eigen_third_party_header_files",
+    srcs = EIGEN3_THIRD_PARTY_HEADERS,
+    visibility = ["//visibility:public"],
+)
+
+genrule(
+    name = "install_eigen_headers",
+    srcs = [
+        "@eigen_archive//:eigen_header_files",
+        ":eigen_third_party_header_files",
+    ],
+    outs = ["include"],
+    cmd = """
+    mkdir $@
+    for f in $(locations @eigen_archive//:eigen_header_files) ; do
+      d="$${f%/*}"
+      d="$${d#*external/eigen_archive/}"
+
+      mkdir -p "$@/$${d}"
+      cp "$${f}" "$@/$${d}/"
+    done
+
+    for f in $(locations :eigen_third_party_header_files) ; do
+      d="$${f%/*}"
+
+      mkdir -p "$@/$${d}"
+      cp "$${f}" "$@/$${d}/"
+    done
+    """
+)