AArch64: Detect crc32 extension support from assembler

The used compiler may or may not be recent enough to recognize the
crc32 extended cpu type. However, it does not really have to know about
them either, since all we do is pass inline assembly instructions to
the assembler.

This patch moves the crc cpu extension detection from compiler based
to assembler based, so that we can build optimized code even when the
compiler does not know about the cpu type yet.

Signed-off-by: Alexander Graf <agraf@suse.de>
(manual backport of e70ab48b7f6d39a281b3ec65098535a55018b681 - manual backport
was undertaken because jewel uses autotools)

diff --git a/m4/ax_arm.m4 b/m4/ax_arm.m4
index 37ea0aaf1d16a41baba741cb6ba528fa151d96f1..26b5258bd6f96b4ed8c23c74223304660579a6ff 100644 (file)
--- a/m4/ax_arm.m4
+++ b/m4/ax_arm.m4
@@ -26,12 +26,19 @@ AC_DEFUN([AX_ARM_FEATURES],
         AC_DEFINE(HAVE_NEON,,[Support NEON instructions])
         AC_SUBST(ARM_NEON_FLAGS)
       fi
-      AX_CHECK_COMPILE_FLAG(-march=armv8-a+crc, ax_cv_support_crc_ext=yes, [])
+
+      AC_LANG_SAVE
+      AC_LANG_CPLUSPLUS
+      AC_CACHE_CHECK(whether the assembler supports crc extensions,
+                     ax_cv_support_crc_ext, AC_TRY_COMPILE([
+          #define CRC32CX(crc, value) __asm__("crc32cx %w[c], %w[c], %x[v]":[c]"+r"(crc):[v]"r"(value))
+          asm(".arch_extension crc");
+          unsigned int foo(unsigned int ret) {
+              CRC32CX(ret, 0);
+              return ret;
+          }],[ foo(0); ], ax_cv_support_crc_ext=yes, []))
       if test x"$ax_cv_support_crc_ext" = x"yes"; then
-        ARM_ARCH_FLAGS="$ARM_ARCH_FLAGS+crc"
-        ARM_CRC_FLAGS="-march=armv8-a+crc -DARCH_AARCH64"
         AC_DEFINE(HAVE_ARMV8_CRC,,[Support ARMv8 CRC instructions])
-        AC_SUBST(ARM_CRC_FLAGS)
       fi
         ARM_FLAGS="$ARM_ARCH_FLAGS $ARM_DEFINE_FLAGS"
     ;;

diff --git a/src/common/Makefile.am b/src/common/Makefile.am
index 8b30eeadec17d05ed305e35266a9aa3c2b521e6d..e92e51c09900e8ec099afa67d042dab22fbef36e 100644 (file)
--- a/src/common/Makefile.am
+++ b/src/common/Makefile.am
@@ -144,7 +144,7 @@ noinst_LTLIBRARIES += libcommon_crc.la
 
 if HAVE_ARMV8_CRC
 libcommon_crc_aarch64_la_SOURCES = common/crc32c_aarch64.c
-libcommon_crc_aarch64_la_CFLAGS = $(AM_CFLAGS) $(ARM_CRC_FLAGS)
+libcommon_crc_aarch64_la_CFLAGS = $(AM_CFLAGS) $(ARM_ARCH_FLAGS)
 LIBCOMMON_DEPS += libcommon_crc_aarch64.la
 noinst_LTLIBRARIES += libcommon_crc_aarch64.la
 endif

diff --git a/src/common/crc32c_aarch64.c b/src/common/crc32c_aarch64.c
index d33827d9e988640cb6f7b0c65c7a3045cce6552e..d2be6ddd85a76b329e4d2ee6a5eb1ef7136ffb1b 100644 (file)
--- a/src/common/crc32c_aarch64.c
+++ b/src/common/crc32c_aarch64.c
@@ -2,6 +2,9 @@
 #include "include/int_types.h"
 #include "common/crc32c_aarch64.h"
 
+/* Request crc extension capabilities from the assembler */
+asm(".arch_extension crc");
+
 #define CRC32CX(crc, value) __asm__("crc32cx %w[c], %w[c], %x[v]":[c]"+r"(crc):[v]"r"(value))
 #define CRC32CW(crc, value) __asm__("crc32cw %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value))
 #define CRC32CH(crc, value) __asm__("crc32ch %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value))