From: Alexander Graf <agraf@suse.de>
Date: Mon, 26 Sep 2016 14:26:37 +0000 (+0200)
Subject: AArch64: Detect crc32 extension support from assembler
X-Git-Tag: v11.1.0~654^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=e70ab48b7f6d39a281b3ec65098535a55018b681;p=ceph.git

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.

Fixes: http://tracker.ceph.com/issues/17516
Signed-off-by: Alexander Graf <agraf@suse.de>
---

diff --git a/cmake/modules/SIMDExt.cmake b/cmake/modules/SIMDExt.cmake
index c531d8ca2f25..a984b51e689d 100644
--- a/cmake/modules/SIMDExt.cmake
+++ b/cmake/modules/SIMDExt.cmake
@@ -16,9 +16,20 @@
 
 if(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64|AARCH64")
   set(HAVE_ARM 1) 
-  CHECK_C_COMPILER_FLAG(-march=armv8-a+crc HAVE_ARMV8_CRC)
+  set(save_quiet ${CMAKE_REQUIRED_QUIET})
+  set(CMAKE_REQUIRED_QUIET true)
+  include(CheckCXXSourceCompiles)
+  check_cxx_source_compiles("
+    #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;
+    }
+    int main() { foo(0); }" HAVE_ARMV8_CRC)
+  set(CMAKE_REQUIRED_QUIET ${save_quiet})
   if(HAVE_ARMV8_CRC)
-    set(ARM_CRC_FLAGS "-march=armv8-a+crc")
+    message(STATUS " aarch64 crc extensions supported")
   endif()
   CHECK_C_COMPILER_FLAG(-march=armv8-a+simd HAVE_ARMV8_SIMD)
   if(HAVE_ARMV8_SIMD)
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index caab0a37cd37..829aea8e2f92 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -488,7 +488,6 @@ set_source_files_properties(${CMAKE_SOURCE_DIR}/src/ceph_ver.c
 include(SIMDExt)
 if(HAVE_ARMV8_CRC)
   add_library(common_crc_aarch64 STATIC common/crc32c_aarch64.c)
-  set_target_properties(common_crc_aarch64 PROPERTIES COMPILE_FLAGS "${CMAKE_C_FLAGS} ${ARM_CRC_FLAGS}")
   target_link_libraries(common common_crc_aarch64)
 endif(HAVE_ARMV8_CRC)
 
diff --git a/src/common/crc32c_aarch64.c b/src/common/crc32c_aarch64.c
index d33827d9e988..d2be6ddd85a7 100644
--- 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))