Support building for Android using NDK

The easiest way to use the NDK in conjunction with this Makefile (tested on linux-x86_64):

1. Download the latest NDK (r21d) from Google from https://developer.android.com/ndk/downloads
2. Place and unzip the NDK in $HOME/ndk folder
3. Export the path variable e.g., `export PATH=$PATH:$HOME/ndk/android-ndk-r21d/toolchains/llvm/prebuilt/linux-x86_64/bin`
4. cd to your Stockfish/src dir
5. Issue `make -j ARCH=armv8 COMP=ndk build`  (use `ARCH=armv7` or `ARCH=armv7-neon` for older CPUs)
6. Optionally `make -j ARCH=armv8 COMP=ndk strip`
7. That's all. Enjoy!

Improves support from Raspberry Pi (incomplete?) and compiling on arm in general

closes https://github.com/official-stockfish/Stockfish/pull/3015

fixes https://github.com/official-stockfish/Stockfish/issues/2860

fixes https://github.com/official-stockfish/Stockfish/issues/2641

Support is still fragile as we're missing CI on these targets. Nevertheless tested with:

```bash
  # build crosses from ubuntu 20.04 on x86 to various arch/OS combos
  # tested with suitable packages installed
  # (build-essentials, mingw-w64, g++-arm-linux-gnueabihf, NDK (r21d) from google)

  # cross to Android
  export PATH=$HOME/ndk/android-ndk-r21d/toolchains/llvm/prebuilt/linux-x86_64/bin:$PATH
  make clean && make -j build ARCH=armv7         COMP=ndk  && make -j build ARCH=armv7 COMP=ndk strip
  make clean && make -j build ARCH=armv7-neon    COMP=ndk  && make -j build ARCH=armv7-neon COMP=ndk strip
  make clean && make -j build ARCH=armv8         COMP=ndk  && make -j build ARCH=armv8 COMP=ndk strip

  # cross to Raspberry Pi
  make clean && make -j build ARCH=armv7         COMP=gcc COMPILER=arm-linux-gnueabihf-g++
  make clean && make -j build ARCH=armv7-neon    COMP=gcc COMPILER=arm-linux-gnueabihf-g++

  # cross to Windows
  make clean && make -j build ARCH=x86-64-modern COMP=mingw
```

No functional change

diff --git a/AUTHORS b/AUTHORS
index 41b89705c973dad1aa82771a9075fab342c762c3..d8f4d30e7c2bc035959eac851bb45658b6116837 100644 (file)
--- a/AUTHORS
+++ b/AUTHORS
@@ -127,6 +127,7 @@ Niklas Fiekas (niklasf)
 Nikolay Kostov (NikolayIT)
 Nguyen Pham (nguyenpham)
 Norman Schmidt (FireFather)
+notruck
 Ondrej Mosnáček (WOnder93)
 Oskar Werkelin Ahlin
 Pablo Vazquez

diff --git a/src/Makefile b/src/Makefile
index 38f607cb24f58fdc2719197be82b82be87e01b04..0f458aa185d608b3429baba9239e6dbb48f9e992 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -102,6 +102,7 @@ avx512 = no
 vnni = no
 neon = no
 ARCH = x86-64-modern
+STRIP = strip
 
 ### 2.2 Architecture specific
 
@@ -208,6 +209,14 @@ ifeq ($(ARCH),armv7)
        bits = 32
 endif
 
+ifeq ($(ARCH),armv7-neon)
+       arch = armv7
+       prefetch = yes
+       popcnt = yes
+       neon = yes
+       bits = 32
+endif
+
 ifeq ($(ARCH),armv8)
        arch = armv8-a
        prefetch = yes
@@ -251,7 +260,7 @@ ifeq ($(COMP),gcc)
        CXX=g++
        CXXFLAGS += -pedantic -Wextra -Wshadow
 
-       ifeq ($(ARCH),$(filter $(ARCH),armv7 armv8))
+       ifeq ($(arch),$(filter $(arch),armv7 armv8-a))
                ifeq ($(OS),Android)
                        CXXFLAGS += -m$(bits)
                        LDFLAGS += -m$(bits)
@@ -261,6 +270,10 @@ ifeq ($(COMP),gcc)
                LDFLAGS += -m$(bits)
        endif
 
+       ifeq ($(arch),$(filter $(arch),armv7))
+               LDFLAGS += -latomic
+       endif
+
        ifneq ($(KERNEL),Darwin)
           LDFLAGS += -Wl,--no-as-needed
        endif
@@ -311,7 +324,7 @@ ifeq ($(COMP),clang)
        endif
        endif
 
-       ifeq ($(ARCH),$(filter $(ARCH),armv7 armv8))
+       ifeq ($(arch),$(filter $(arch),armv7 armv8))
                ifeq ($(OS),Android)
                        CXXFLAGS += -m$(bits)
                        LDFLAGS += -m$(bits)
@@ -340,6 +353,25 @@ ifeq ($(KERNEL),Darwin)
        LDFLAGS += -arch $(arch) -mmacosx-version-min=10.14
 endif
 
+# To cross-compile for Android, NDK version r21 or later is recommended.
+# In earlier NDK versions, you'll need to pass -fno-addrsig if using GNU binutils.
+# Currently we don't know how to make PGO builds with the NDK yet.
+ifeq ($(COMP),ndk)
+       CXXFLAGS += -stdlib=libc++ -fPIE
+       ifeq ($(arch),armv7)
+               comp=armv7a-linux-androideabi16-clang
+               CXX=armv7a-linux-androideabi16-clang++
+               CXXFLAGS += -mthumb -march=armv7-a -mfloat-abi=softfp -mfpu=neon
+               STRIP=arm-linux-androideabi-strip
+       endif
+       ifeq ($(arch),armv8-a)
+               comp=aarch64-linux-android21-clang
+               CXX=aarch64-linux-android21-clang++
+               STRIP=aarch64-linux-android-strip
+       endif
+       LDFLAGS += -static-libstdc++ -pie -lm -latomic
+endif
+
 ### Travis CI script uses COMPILER to overwrite CXX
 ifdef COMPILER
        COMPCXX=$(COMPILER)
@@ -356,7 +388,9 @@ ifneq ($(comp),mingw)
        ifneq ($(OS),Android)
                # Haiku has pthreads in its libroot, so only link it in on other platforms
                ifneq ($(KERNEL),Haiku)
-                       LDFLAGS += -lpthread
+                       ifneq ($(COMP),ndk)
+                               LDFLAGS += -lpthread
+                       endif
                endif
        endif
 endif
@@ -401,7 +435,6 @@ endif
 ifeq ($(prefetch),yes)
        ifeq ($(sse),yes)
                CXXFLAGS += -msse
-               DEPENDFLAGS += -msse
        endif
 else
        CXXFLAGS += -DNO_PREFETCH
@@ -409,7 +442,7 @@ endif
 
 ### 3.6 popcnt
 ifeq ($(popcnt),yes)
-       ifeq ($(arch),$(filter $(arch),ppc64 armv8-a arm64))
+       ifeq ($(arch),$(filter $(arch),ppc64 armv7 armv8-a arm64))
                CXXFLAGS += -DUSE_POPCNT
        else ifeq ($(comp),icc)
                CXXFLAGS += -msse3 -DUSE_POPCNT
@@ -418,6 +451,7 @@ ifeq ($(popcnt),yes)
        endif
 endif
 
+
 ifeq ($(avx2),yes)
        CXXFLAGS += -DUSE_AVX2
        ifeq ($(comp),$(filter $(comp),gcc clang mingw))
@@ -462,6 +496,11 @@ endif
 
 ifeq ($(neon),yes)
        CXXFLAGS += -DUSE_NEON
+       ifeq ($(KERNEL),Linux)
+       ifneq ($(COMP),ndk)
+               CXXFLAGS += -mfpu=neon
+       endif
+       endif
 endif
 
 ifeq ($(arch),x86_64)
@@ -481,7 +520,10 @@ endif
 ### needs access to the optimization flags.
 ifeq ($(optimize),yes)
 ifeq ($(debug), no)
-       ifeq ($(comp),clang)
+       ifeq ($(COMP),ndk)
+               CXXFLAGS += -flto=thin
+               LDFLAGS += $(CXXFLAGS)
+       else ifeq ($(comp),clang)
                CXXFLAGS += -flto=thin
                LDFLAGS += $(CXXFLAGS)
 
@@ -502,7 +544,7 @@ ifeq ($(debug), no)
        endif
 
 # To use LTO and static linking on windows, the tool chain requires a recent gcc:
-# gcc version 10.1 in msys2 or TDM-GCC version 9.2 are know to work, older might not.
+# gcc version 10.1 in msys2 or TDM-GCC version 9.2 are known to work, older might not.
 # So, only enable it for a cross from Linux by default.
        else ifeq ($(comp),mingw)
        ifeq ($(KERNEL),Linux)
@@ -556,7 +598,8 @@ help:
        @echo "ppc-64                  > PPC 64-bit"
        @echo "ppc-32                  > PPC 32-bit"
        @echo "armv7                   > ARMv7 32-bit"
-       @echo "armv8                   > ARMv8 64-bit"
+       @echo "armv7-neon"             > ARMv7 32-bit with popcnt and neon"
+       @echo "armv8                   > ARMv8 64-bit with popcnt and neon"
        @echo "apple-silicon           > Apple silicon ARM64"
        @echo "general-64              > unspecified 64-bit"
        @echo "general-32              > unspecified 32-bit"
@@ -567,6 +610,7 @@ help:
        @echo "mingw                   > Gnu compiler with MinGW under Windows"
        @echo "clang                   > LLVM Clang compiler"
        @echo "icc                     > Intel compiler"
+       @echo "ndk                     > Google NDK to cross-compile for Android"
        @echo ""
        @echo "Simple examples. If you don't know what to do, you likely want to run: "
        @echo ""
@@ -609,7 +653,7 @@ profile-build: net config-sanity objclean profileclean
        $(MAKE) ARCH=$(ARCH) COMP=$(COMP) profileclean
 
 strip:
-       strip $(EXE)
+       $(STRIP) $(EXE)
 
 install:
        -mkdir -p -m 755 $(BINDIR)
@@ -693,7 +737,8 @@ config-sanity:
        @test "$(avx512)" = "yes" || test "$(avx512)" = "no"
        @test "$(vnni)" = "yes" || test "$(vnni)" = "no"
        @test "$(neon)" = "yes" || test "$(neon)" = "no"
-       @test "$(comp)" = "gcc" || test "$(comp)" = "icc" || test "$(comp)" = "mingw" || test "$(comp)" = "clang"
+       @test "$(comp)" = "gcc" || test "$(comp)" = "icc" || test "$(comp)" = "mingw" || test "$(comp)" = "clang" \
+       || test "$(comp)" = "armv7a-linux-androideabi16-clang"  || test "$(comp)" = "aarch64-linux-android21-clang"
 
 $(EXE): $(OBJS)
        +$(CXX) -o $@ $(OBJS) $(LDFLAGS)