gnu: Add FP16.

* gnu/packages/patches/fp16-system-libraries.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/maths.scm (fp16): New variable.

gnu/local.mk

@@ -1028,6 +1028,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/foomatic-filters-CVE-2015-8327.patch	\
   %D%/packages/patches/foomatic-filters-CVE-2015-8560.patch	\
   %D%/packages/patches/fontconfig-hurd-path-max.patch		\
+  %D%/packages/patches/fp16-system-libraries.patch		\
   %D%/packages/patches/fpc-reproducibility.patch		\
   %D%/packages/patches/fplll-std-fenv.patch     		\
   %D%/packages/patches/freedink-engine-fix-sdl-hints.patch	\

gnu/packages/maths.scm

@@ -6688,3 +6688,33 @@ multiplication.  FXdiv implements an algorithm to replace an integer division
 with a multiplication and two shifts.  This algorithm improves performance
 when an application performs repeated divisions by the same divisor.")
       (license license:expat))))
+
+(define-public fp16
+  ;; There is currently no tag in this repo.
+  (let ((commit "0a92994d729ff76a58f692d3028ca1b64b145d91")
+        (version "0.0")
+        (revision "1"))
+    (package
+      (name "fp16")
+      (version (git-version version revision commit))
+      (home-page "https://github.com/Maratyszcza/FP16")
+      (source (origin
+                (method git-fetch)
+                (uri (git-reference (url home-page) (commit commit)))
+                (file-name (git-file-name name version))
+                (sha256
+                 (base32
+                  "05mm4vrxsac35hjf5djif9r6rdxj9ippg97ia3p6q6b8lrp7srwv"))
+                (patches (search-patches "fp16-system-libraries.patch"))))
+      (build-system cmake-build-system)
+      (native-inputs
+       `(("python-wrapper" ,python-wrapper)))
+      (inputs
+       `(("psimd" ,psimd)
+         ("googletest" ,googletest)
+         ("googlebenchmark" ,googlebenchmark)))
+      (synopsis "C++ library for half-precision floating point formats")
+      (description
+       "This header-only C++ library implements conversion to and from
+half-precision floating point formats.")
+      (license license:expat))))

gnu/packages/patches/fp16-system-libraries.patch

@@ -0,0 +1,105 @@
+This patch allows the build process to use the provided dependencies instead
+of adding their source as CMake sub-directories (in which case "make install"
+would install googletest's and googlebenchmark's libraries and headers).
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 5e7d127..4b269b9 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -28,7 +28,7 @@ MACRO(FP16_TARGET_ENABLE_CXX11 target)
+ ENDMACRO()
+ 
+ # ---[ Download deps
+-IF(NOT DEFINED PSIMD_SOURCE_DIR)
++IF(FALSE)
+   MESSAGE(STATUS "Downloading PSimd to ${CMAKE_BINARY_DIR}/psimd-source (define PSIMD_SOURCE_DIR to avoid it)")
+   CONFIGURE_FILE(cmake/DownloadPSimd.cmake "${CMAKE_BINARY_DIR}/psimd-download/CMakeLists.txt")
+   EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
+@@ -38,7 +38,7 @@ IF(NOT DEFINED PSIMD_SOURCE_DIR)
+   SET(PSIMD_SOURCE_DIR "${CMAKE_BINARY_DIR}/psimd-source" CACHE STRING "PSimd source directory")
+ ENDIF()
+ 
+-IF(FP16_BUILD_TESTS AND NOT DEFINED GOOGLETEST_SOURCE_DIR)
++IF(FALSE)
+   MESSAGE(STATUS "Downloading Google Test to ${CMAKE_BINARY_DIR}/googletest-source (define GOOGLETEST_SOURCE_DIR to avoid it)")
+   CONFIGURE_FILE(cmake/DownloadGoogleTest.cmake "${CMAKE_BINARY_DIR}/googletest-download/CMakeLists.txt")
+   EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
+@@ -48,7 +48,7 @@ IF(FP16_BUILD_TESTS AND NOT DEFINED GOOGLETEST_SOURCE_DIR)
+   SET(GOOGLETEST_SOURCE_DIR "${CMAKE_BINARY_DIR}/googletest-source" CACHE STRING "Google Test source directory")
+ ENDIF()
+ 
+-IF(FP16_BUILD_BENCHMARKS AND NOT DEFINED GOOGLEBENCHMARK_SOURCE_DIR)
++IF(FALSE)
+   MESSAGE(STATUS "Downloading Google Benchmark to ${CMAKE_BINARY_DIR}/googlebenchmark-source (define GOOGLEBENCHMARK_SOURCE_DIR to avoid it)")
+   CONFIGURE_FILE(cmake/DownloadGoogleBenchmark.cmake "${CMAKE_BINARY_DIR}/googlebenchmark-download/CMakeLists.txt")
+   EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
+@@ -84,22 +84,7 @@ INSTALL(FILES
+     include/fp16/avx2.py
+   DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/fp16)
+ 
+-# ---[ Configure psimd
+-IF(NOT TARGET psimd)
+-  ADD_SUBDIRECTORY(
+-    "${PSIMD_SOURCE_DIR}"
+-    "${CMAKE_BINARY_DIR}/psimd")
+-ENDIF()
+-
+ IF(FP16_BUILD_TESTS)
+-  # ---[ Build google test
+-  IF(NOT TARGET gtest)
+-    SET(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+-    ADD_SUBDIRECTORY(
+-      "${GOOGLETEST_SOURCE_DIR}"
+-      "${CMAKE_BINARY_DIR}/googletest")
+-  ENDIF()
+-
+   # ---[ Build FP16 unit tests
+   ADD_EXECUTABLE(ieee-to-fp32-bits-test test/ieee-to-fp32-bits.cc test/tables.cc)
+   TARGET_INCLUDE_DIRECTORIES(ieee-to-fp32-bits-test PRIVATE test)
+@@ -137,40 +122,32 @@ IF(FP16_BUILD_TESTS)
+ ENDIF()
+ 
+ IF(FP16_BUILD_BENCHMARKS)
+-  # ---[ Build google benchmark
+-  IF(NOT TARGET benchmark)
+-    SET(BENCHMARK_ENABLE_TESTING OFF CACHE BOOL "")
+-    ADD_SUBDIRECTORY(
+-      "${GOOGLEBENCHMARK_SOURCE_DIR}"
+-      "${CMAKE_BINARY_DIR}/googlebenchmark")
+-  ENDIF()
+-
+   # ---[ Build FP16 benchmarks
+   ADD_EXECUTABLE(ieee-element-bench bench/ieee-element.cc)
+   TARGET_COMPILE_DEFINITIONS(ieee-element-bench PRIVATE FP16_COMPARATIVE_BENCHMARKS=1)
+   TARGET_INCLUDE_DIRECTORIES(ieee-element-bench PRIVATE ${PROJECT_SOURCE_DIR})
+-  TARGET_LINK_LIBRARIES(ieee-element-bench fp16 psimd benchmark)
++  TARGET_LINK_LIBRARIES(ieee-element-bench fp16 benchmark)
+ 
+   ADD_EXECUTABLE(alt-element-bench bench/alt-element.cc)
+-  TARGET_LINK_LIBRARIES(alt-element-bench fp16 psimd benchmark)
++  TARGET_LINK_LIBRARIES(alt-element-bench fp16 benchmark)
+ 
+   ADD_EXECUTABLE(from-ieee-array-bench bench/from-ieee-array.cc)
+   FP16_TARGET_ENABLE_CXX11(from-ieee-array-bench)
+   TARGET_COMPILE_DEFINITIONS(from-ieee-array-bench PRIVATE FP16_COMPARATIVE_BENCHMARKS=1)
+   TARGET_INCLUDE_DIRECTORIES(from-ieee-array-bench PRIVATE ${PROJECT_SOURCE_DIR})
+-  TARGET_LINK_LIBRARIES(from-ieee-array-bench fp16 psimd benchmark)
++  TARGET_LINK_LIBRARIES(from-ieee-array-bench fp16 benchmark)
+ 
+   ADD_EXECUTABLE(from-alt-array-bench bench/from-alt-array.cc)
+   FP16_TARGET_ENABLE_CXX11(from-alt-array-bench)
+-  TARGET_LINK_LIBRARIES(from-alt-array-bench fp16 psimd benchmark)
++  TARGET_LINK_LIBRARIES(from-alt-array-bench fp16 benchmark)
+ 
+   ADD_EXECUTABLE(to-ieee-array-bench bench/to-ieee-array.cc)
+   FP16_TARGET_ENABLE_CXX11(to-ieee-array-bench)
+   TARGET_COMPILE_DEFINITIONS(to-ieee-array-bench PRIVATE FP16_COMPARATIVE_BENCHMARKS=1)
+   TARGET_INCLUDE_DIRECTORIES(to-ieee-array-bench PRIVATE ${PROJECT_SOURCE_DIR})
+-  TARGET_LINK_LIBRARIES(to-ieee-array-bench fp16 psimd benchmark)
++  TARGET_LINK_LIBRARIES(to-ieee-array-bench fp16 benchmark)
+ 
+   ADD_EXECUTABLE(to-alt-array-bench bench/to-alt-array.cc)
+   FP16_TARGET_ENABLE_CXX11(to-alt-array-bench)
+-  TARGET_LINK_LIBRARIES(to-alt-array-bench fp16 psimd benchmark)
++  TARGET_LINK_LIBRARIES(to-alt-array-bench fp16 benchmark)
+ ENDIF()