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).

1 files changed, 7 insertions, 2 deletions

diff --git a/src/liblzma/check/crc32_fast.c b/src/liblzma/check/crc32_fast.c
index 9fce94d3..6982836a 100644
--- a/src/liblzma/check/crc32_fast.c
+++ b/src/liblzma/check/crc32_fast.c
@@ -15,6 +15,11 @@
 #include "check.h"
 #include "crc_common.h"
 
+#ifdef CRC_CLMUL
+#	define BUILDING_CRC32_CLMUL
+#	include "crc_x86_clmul.h"
+#endif
+
 
 #ifdef CRC_GENERIC
 
@@ -132,7 +137,7 @@ typedef uint32_t (*crc32_func_type)(
 static crc32_func_type
 crc32_resolve(void)
 {
-	return is_clmul_supported() ? &lzma_crc32_clmul : &crc32_generic;
+	return is_clmul_supported() ? &crc32_clmul : &crc32_generic;
 }
 
 #if defined(HAVE_FUNC_ATTRIBUTE_IFUNC) && defined(__clang__)
@@ -221,7 +226,7 @@ lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
 	return crc32_func(buf, size, crc);
 
 #elif defined(CRC_CLMUL)
-	return lzma_crc32_clmul(buf, size, crc);
+	return crc32_clmul(buf, size, crc);
 
 #else
 	return crc32_generic(buf, size, crc);