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authorLasse Collin <lasse.collin@tukaani.org>2023-10-20 23:35:10 +0300
committerLasse Collin <lasse.collin@tukaani.org>2024-01-11 14:29:42 +0200
commit419f55f9dfc2df8792902b8953d50690121afeea (patch)
treeaa95af5e4119ab90423c19ad64cfa73df0044f1c /configure.ac
parentliblzma: crc_clmul.c: Add crc_attr_target macro. (diff)
downloadxz-419f55f9dfc2df8792902b8953d50690121afeea.tar.xz
liblzma: Avoid extern lzma_crc32_clmul() and lzma_crc64_clmul().
A CLMUL-only build will have the crcxx_clmul() inlined into lzma_crcxx(). Previously a jump to the extern lzma_crcxx_clmul() was needed. Notes about shared liblzma on ELF platforms: - On platforms that support ifunc and -fvisibility=hidden, this was silly because CLMUL-only build would have that single extra jump instruction of extra overhead. - On platforms that support neither -fvisibility=hidden nor linker version script (liblzma*.map), jumping to lzma_crcxx_clmul() would go via PLT so a few more instructions of overhead (still not a big issue but silly nevertheless). There was a downside with static liblzma too: if an application only needs lzma_crc64(), static linking would make the linker include the CLMUL code for both CRC32 and CRC64 from crc_x86_clmul.o even though the CRC32 code wouldn't be needed, thus increasing code size of the executable (assuming that -ffunction-sections isn't used). Also, now compilers are likely to inline crc_simd_body() even if they don't support the always_inline attribute (or MSVC's __forceinline). Quite possibly all compilers that build the code do support such an attribute. But now it likely isn't a problem even if the attribute wasn't supported. Now all x86-specific stuff is in crc_x86_clmul.h. If other archs The other archs can then have their own headers with their own is_clmul_supported() and crcxx_clmul(). Another bonus is that the build system doesn't need to care if crc_clmul.c is needed. is_clmul_supported() stays as inline function as it's not needed when doing a CLMUL-only build (avoids a warning about unused function).
Diffstat (limited to 'configure.ac')
-rw-r--r--configure.ac1
1 files changed, 0 insertions, 1 deletions
diff --git a/configure.ac b/configure.ac
index a4ef57a5..9584c4ac 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1086,7 +1086,6 @@ __m128i my_clmul(__m128i a)
])
AC_MSG_RESULT([$enable_clmul_crc])
])
-AM_CONDITIONAL([COND_CRC_CLMUL], [test "x$enable_clmul_crc" = xyes])
# Check for sandbox support. If one is found, set enable_sandbox=found.
#