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From: Liang Li <liang.z.li@intel.com>
Date: Tue,  8 Dec 2015 20:08:54 +0800
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Subject: [Qemu-devel] [v3 2/3] configure: detect ifunc attribute
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To: qemu-devel@nongnu.org
Cc: Liang Li <liang.z.li@intel.com>, quintela@redhat.com, mst@redhat.com, dgilbert@redhat.com, stefanha@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, rth@twiddle.net

Detect if the compiler can support the ifunc attribute, the avx2
optimization depends on ifunc attribute.

Signed-off-by: Liang Li <liang.z.li@intel.com>
---
 configure | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/configure b/configure
index b9552fd..394db3b 100755
--- a/configure
+++ b/configure
@@ -310,6 +310,7 @@ smartcard=""
 libusb=""
 usb_redir=""
 opengl=""
+ifunc=""
 zlib="yes"
 lzo=""
 snappy=""
@@ -1827,6 +1828,20 @@ EOF
 fi
 
 ##########################################
+# ifunc check
+
+cat > $TMPC << EOF
+static void bar(void) {}
+static void foo(void) __attribute__((ifunc("bar")));
+int main(void) { foo(); return 0; }
+EOF
+if compile_prog "" "" ; then
+    ifunc="yes"
+else
+    ifunc="no"
+fi
+
+#########################################
 # zlib check
 
 if test "$zlib" != "no" ; then
@@ -4837,6 +4852,7 @@ echo "libssh2 support   $libssh2"
 echo "TPM passthrough   $tpm_passthrough"
 echo "QOM debugging     $qom_cast_debug"
 echo "vhdx              $vhdx"
+echo "ifunc support     $ifunc"
 echo "lzo support       $lzo"
 echo "snappy support    $snappy"
 echo "bzip2 support     $bzip2"
@@ -5221,6 +5237,10 @@ if test "$opengl" = "yes" ; then
   echo "OPENGL_LIBS=$opengl_libs" >> $config_host_mak
 fi
 
+if test "$ifunc" = "yes" ; then
+  echo "CONFIG_IFUNC=y" >> $config_host_mak
+fi
+
 if test "$lzo" = "yes" ; then
   echo "CONFIG_LZO=y" >> $config_host_mak
 fi
-- 
1.9.1