A previous version of this was submitted and rolled back due to breakage
-- an attempt to accommodate Visual Studio resulted in compiler errors
on GCC/Clang with -mavx2 but without -mbmi2. This version makes the BMI2
support check more strict, to avoid the errors.
A previous CL introduced _bzhi_u32 (part of Intel's BMI2 instruction
set, released in Haswell) gated by a check for the __BMI2__ preprocessor
macro. This works for Clang and GCC, but does not work on Visual Studio,
and may not work on other compilers.
This CL plumbs the BMI2 support checks through the CMake configuration
used by the open source build. It also replaces the <x86intrin.h>
header, which does not exist on Visual Studio, with the more scoped
headers <tmmintrin.h> (for SSSE3) and <immintrin.h> (for BMI2/AVX2).
Asides from fixing the open source build, the more scoped headers make
it slightly less likely that newer intrinsics will creep in without
proper gating.
Commit 8f469d97e2 introduced SSSE3 fast
paths that are gated by __SSE3__ macro checks and the <x86intrin.h>
header, neither of which exists in Visual Studio. This commit adds logic
for detecting SSSE3 compiler support that works for all compilers
supported by the open source release.
The commit also replaces the header with <tmmintrin.h>, which only
defines intrinsics supported by SSSE3 and below. This should help flag
any use of SIMD instructions that require more advanced SSE support, so
the uses can be gated by checks that also work in the open source
release.
Last, this commit requires C++11 support for the open source build. This is
needed by the alignas specifier, which was also introduced in commit
8f469d97e2.
getpagesize(), as well as its POSIX.2001 replacement
sysconf(_SC_PAGESIZE), is defined in <unistd.h>. On Linux and OS X,
including <sys/mman.h> is sufficient to get a definition for
getpagesize(). However, this is not true for the Android NDK. This CL
brings back the HAVE_UNISTD_H definition and its associated header
check.
This also adds a HAVE_FUNC_SYSCONF definition, which checks for the
presence of sysconf(). The definition can be used later to replace
getpagesize() with sysconf().
The style was changed to match the official manual [1], the install
configuration was simplified and now matches the official packaging
guide [2], and the config files use the CMake-specific variable syntax
${VAR} instead of the autoconf-compatible syntax @VAR@, as documented in
[3]. The public header files are declared as such (for CMake 3.3+), and
the generated headers are included in the library target definition.
The tests are only built if SNAPPY_BUILD_TESTS (default ON) is true, so
zippy can be easily used in projects that add_subdirectory() its source
code directly, instead of using find_package().
[1] https://cmake.org/cmake/help/git-master/manual/cmake-language.7.html
[2] https://cmake.org/cmake/help/git-master/manual/cmake-packages.7.html
[3] https://cmake.org/cmake/help/git-master/command/configure_file.html
Unused macros: HAVE_DLFCN_H, HAVE_INTTYPES_H, HAVE_MEMORY_H,
HAVE_STDLIB_H, HAVE_STRINGS_H, HAVE_STRING_H, HAVE_SYS_BYTESWAP_H,
HAVE_SYS_STAT_H, HAVE_SYS_TYPES_H, HAVE_UNISTD_H.
Used but never set macros: HAVE_LIBLZF, HAVE_LIBQUICKLZ. These only gate
conditional includes. The code that takes advantage of them was removed.
Unused types: ssize_t.
The testing code uses HAVE_FUNC_MMAP, which was not wired in the CMake
build, causing a whole test to be skipped.
