From e9d3951bb6860b45a9487dee59c34ccde443f735 Mon Sep 17 00:00:00 2001
From: Amos Jeffries <squid3@treenet.co.nz>
Date: Mon, 20 May 2013 23:39:18 -0600
Subject: [PATCH] Detect and use -march=natuve when possible

Clang++ 3.2 fails to detect some CPUs correctly and requires the
additional checks enabled by this option to build working executables.

This option supported by GCC 4.3 and later enables additional CPU
detection and enables CPU-specific optimizations. In the interests of
better performance this patch enables it whenever is it available and
possible to use (cross-compilers cannot use it).
---
 configure.ac | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index f2e45c0a7c..3108ea7062 100644
--- a/configure.ac
+++ b/configure.ac
@@ -35,9 +35,20 @@ AC_PROG_CXX
 AC_LANG([C++])
 AC_CANONICAL_HOST
 
-# might be cross-compiling
+# Clang 3.2 on some CPUs requires -march-native to detect correctly
+# GCC 4.3+ can also produce faster executables when its used
+SQUID_CC_CHECK_ARGUMENT([squid_cv_check_marchnative],[-march=native])
+
+# might be cross-compiling.
 if test "x$HOSTCXX" = "x"; then
   HOSTCXX="$CXX"
+  if test "x$squid_cv_check_marchnative" = "xyes"; then
+    CXXFLAGS="$CXXFLAGS -march=native"
+  fi
+fi
+if test "x$squid_cv_check_marchnative" = "xyes"; then
+  # always valid for the Host compiler.
+  HOSTCXX="$HOSTCXX -march=native"
 fi
 AC_SUBST(HOSTCXX)
 
-- 
2.47.3