Build: Add very limited experimental CMake support.

This version matches CMake files in the master branch (commit
265daa873c0d871f5f23f9b56e133a6f20045a0a) except that this omits
two source files that aren't in v5.2 and in the beginning of
CMakeLists.txt the first paragraph in the comment is slightly
different to point out possible issues in building shared liblzma.

1 files changed, 102 insertions, 0 deletions

diff --git a/cmake/tuklib_integer.cmake b/cmake/tuklib_integer.cmake
new file mode 100644
index 00000000..d7e2e28c
--- /dev/null
+++ b/cmake/tuklib_integer.cmake
@@ -0,0 +1,102 @@
+#
+# tuklib_integer.cmake - see tuklib_integer.m4 for description and comments
+#
+# Author: Lasse Collin
+#
+# This file has been put into the public domain.
+# You can do whatever you want with this file.
+#
+
+include("${CMAKE_CURRENT_LIST_DIR}/tuklib_common.cmake")
+include(TestBigEndian)
+include(CheckCSourceCompiles)
+include(CheckIncludeFile)
+include(CheckSymbolExists)
+
+function(tuklib_integer TARGET_OR_ALL)
+    # Check for endianness. Unlike the Autoconf's AC_C_BIGENDIAN, this doesn't
+    # support Apple universal binaries. The CMake module will leave the
+    # variable unset so we can catch that situation here instead of continuing
+    # as if we were little endian.
+    test_big_endian(WORDS_BIGENDIAN)
+    if(NOT DEFINED WORDS_BIGENDIAN)
+        message(FATAL_ERROR "Cannot determine endianness")
+    endif()
+    tuklib_add_definition_if("${TARGET_OR_ALL}" WORDS_BIGENDIAN)
+
+    # Look for a byteswapping method.
+    check_c_source_compiles("
+            int main(void)
+            {
+                __builtin_bswap16(1);
+                __builtin_bswap32(1);
+                __builtin_bswap64(1);
+                return 0;
+            }
+        "
+        HAVE___BUILTIN_BSWAPXX)
+    if(HAVE___BUILTIN_BSWAPXX)
+        tuklib_add_definitions("${TARGET_OR_ALL}" HAVE___BUILTIN_BSWAPXX)
+    else()
+        check_include_file(byteswap.h HAVE_BYTESWAP_H)
+        if(HAVE_BYTESWAP_H)
+            tuklib_add_definitions("${TARGET_OR_ALL}" HAVE_BYTESWAP_H)
+            check_symbol_exists(bswap_16 byteswap.h HAVE_BSWAP_16)
+            tuklib_add_definition_if("${TARGET_OR_ALL}" HAVE_BSWAP_16)
+            check_symbol_exists(bswap_32 byteswap.h HAVE_BSWAP_32)
+            tuklib_add_definition_if("${TARGET_OR_ALL}" HAVE_BSWAP_32)
+            check_symbol_exists(bswap_64 byteswap.h HAVE_BSWAP_64)
+            tuklib_add_definition_if("${TARGET_OR_ALL}" HAVE_BSWAP_64)
+        else()
+            check_include_file(sys/endian.h HAVE_SYS_ENDIAN_H)
+            if(HAVE_SYS_ENDIAN_H)
+                tuklib_add_definitions("${TARGET_OR_ALL}" HAVE_SYS_ENDIAN_H)
+            else()
+                check_include_file(sys/byteorder.h HAVE_SYS_BYTEORDER_H)
+                tuklib_add_definition_if("${TARGET_OR_ALL}"
+                                         HAVE_SYS_BYTEORDER_H)
+            endif()
+        endif()
+    endif()
+
+    # 16-bit and 32-bit unaligned access is fast on x86(-64),
+    # big endian PowerPC, and usually on 32/64-bit ARM too.
+    # There are others too and ARM could be a false match.
+    #
+    # Guess the default value for the option.
+    # CMake's ability to give info about the target arch seems bad.
+    # The the same arch can have different name depending on the OS.
+    #
+    # FIXME: The regex is based on guessing, not on factual information!
+    #
+    # NOTE: Compared to the Autoconf test, this lacks the GCC/Clang test
+    #       on ARM and always assumes that unaligned is fast on ARM.
+    set(FAST_UNALIGNED_GUESS OFF)
+    if(CMAKE_SYSTEM_PROCESSOR MATCHES
+       "[Xx3456]86|^[Xx]64|^[Aa][Mm][Dd]64|^[Aa][Rr][Mm]|^aarch|^powerpc|^ppc")
+        if(NOT WORDS_BIGENDIAN OR
+           NOT CMAKE_SYSTEM_PROCESSOR MATCHES "^powerpc|^ppc")
+           set(FAST_UNALIGNED_GUESS ON)
+        endif()
+    endif()
+    option(TUKLIB_FAST_UNALIGNED_ACCESS
+           "Enable if the system supports *fast* unaligned memory access \
+with 16-bit and 32-bit integers."
+           "${FAST_UNALIGNED_GUESS}")
+    tuklib_add_definition_if("${TARGET_OR_ALL}" TUKLIB_FAST_UNALIGNED_ACCESS)
+
+    # Unsafe type punning:
+    option(TUKLIB_USE_UNSAFE_TYPE_PUNNING
+           "This introduces strict aliasing violations and \
+may result in broken code. However, this might improve performance \
+in some cases, especially with old compilers \
+(e.g. GCC 3 and early 4.x on x86, GCC < 6 on ARMv6 and ARMv7)."
+           OFF)
+    tuklib_add_definition_if("${TARGET_OR_ALL}" TUKLIB_USE_UNSAFE_TYPE_PUNNING)
+
+    # Check for GCC/Clang __builtin_assume_aligned().
+    check_c_source_compiles(
+        "int main(void) { __builtin_assume_aligned(\"\", 1); return 0; }"
+        HAVE___BUILTIN_ASSUME_ALIGNED)
+    tuklib_add_definition_if("${TARGET_OR_ALL}" HAVE___BUILTIN_ASSUME_ALIGNED)
+endfunction()