liblzma: Add fast CRC64 for 32/64-bit x86 using SSSE3 + SSE4.1 + CLMUL.

It also works on E2K as it supports these intrinsics.

On x86-64 runtime detection is used so the code keeps working on
older processors too. A CLMUL-only build can be done by using
-msse4.1 -mpclmul in CFLAGS and this will reduce the library
size since the generic implementation and its 8 KiB lookup table
will be omitted.

On 32-bit x86 this isn't used by default for now because by default
on 32-bit x86 the separate assembly file crc64_x86.S is used.
If --disable-assembler is used then this new CLMUL code is used
the same way as on 64-bit x86. However, a CLMUL-only build
(-msse4.1 -mpclmul) won't omit the 8 KiB lookup table on
32-bit x86 due to a currently-missing check for disabled
assembler usage.

The configure.ac check should be such that the code won't be
built if something in the toolchain doesn't support it but
--disable-clmul-crc option can be used to unconditionally
disable this feature.

CLMUL speeds up decompression of files that have compressed very
well (assuming CRC64 is used as a check type). It is know that
the CLMUL code is significantly slower than the generic code for
tiny inputs (especially 1-8 bytes but up to 16 bytes). If that
is a real-world problem then there is already a commented-out
variant that uses the generic version for small inputs.

Thanks to Ilya Kurdyukov for the original patch which was
derived from a white paper from Intel [1] (published in 2009)
and public domain code from [2] (released in 2016).

[1] https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf
[2] https://github.com/rawrunprotected/crc

1 files changed, 57 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index ddc82a3b..60a63825 100644
--- a/configure.ac
+++ b/configure.ac
@@ -370,6 +370,16 @@ esac
 AM_CONDITIONAL(COND_ASM_X86, test "x$enable_assembler" = xx86)
 
 
+#############
+# CLMUL CRC #
+#############
+
+AC_ARG_ENABLE([clmul-crc], AS_HELP_STRING([--disable-clmul-crc],
+		[Do not use carryless multiplication for CRC calculation
+		even if support for it is detected.]),
+	[], [enable_clmul_crc=yes])
+
+
 #####################
 # Size optimization #
 #####################
@@ -733,8 +743,9 @@ AC_CHECK_HEADERS([fcntl.h limits.h sys/time.h],
 	[],
 	[AC_MSG_ERROR([Required header file(s) are missing.])])
 
-# This allows the use of the intrinsic functions if they are available.
-AC_CHECK_HEADERS([immintrin.h])
+# immintrin.h allows the use of the intrinsic functions if they are available.
+# cpuid.h may be used for detecting x86 processor features at runtime.
+AC_CHECK_HEADERS([immintrin.h cpuid.h])
 
 
 ###############################################################################
@@ -874,6 +885,50 @@ AC_CHECK_DECL([_mm_movemask_epi8],
 #include <immintrin.h>
 #endif])
 
+# For faster CRC on 32/64-bit x86 and E2K (see also crc64_fast.c):
+#
+#   - Check for the CLMUL intrinsic _mm_clmulepi64_si128 in <immintrin.h>.
+#
+#   - Check that __attribute__((__target__("ssse3,sse4.1,pclmul"))) works
+#     together with _mm_clmulepi64_si128 from <immintrin.h>. The attribute
+#     was added in GCC 4.4 but some GCC 4.x versions don't allow intrinsics
+#     with it. Exception: it must be not be used with EDG-based compilers
+#     like ICC and the compiler on E2K.
+#
+# If everything above is supported, runtime detection will be used to keep the
+# binaries working on systems that don't support the required extensions.
+AC_MSG_CHECKING([if _mm_clmulepi64_si128 is usable])
+if test "x$enable_clmul_crc" = xno ; then
+	AC_MSG_RESULT([no, --disable-clmul-crc was used])
+else
+	AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+#include <immintrin.h>
+
+// CLMUL works on older E2K instruction set but it is slow due to emulation.
+#if defined(__e2k__) && __iset__ < 6
+#	error
+#endif
+
+// Intel's old compiler (ICC) can define __GNUC__ but the attribute must not
+// be used with it. The new Clang-based ICX needs the attribute.
+// Checking for !defined(__EDG__) catches ICC and other EDG-based compilers.
+#if (defined(__GNUC__) || defined(__clang__)) && !defined(__EDG__)
+__attribute__((__target__("ssse3,sse4.1,pclmul")))
+#endif
+__m128i my_clmul(__m128i a, __m128i b)
+{
+	return _mm_clmulepi64_si128(a, b, 0);
+}
+	]])], [
+		AC_DEFINE([HAVE_USABLE_CLMUL], [1],
+			[Define to 1 if _mm_clmulepi64_si128 is usable.
+			See configure.ac for details.])
+		AC_MSG_RESULT([yes])
+	], [
+		AC_MSG_RESULT([no])
+	])
+fi
+
 # Check for sandbox support. If one is found, set enable_sandbox=found.
 case $enable_sandbox in
 	auto | capsicum)