Makefile: allow specifying custom -march for clang

Useful to build and use S2E in VirtualBox, which does
not support AVX instructions, causing SIGILL.

Signed-off-by: Vitaly Chipounov <[email protected]>

Author: Vitaly Chipounov

Makefile

@@ -1,3 +1,13 @@
+#Environment variables:
+#
+#  BUILD_ARCH=corei7, etc...
+#      Overrides the default clang -march settings.
+#      Useful to build S2E in VirtualBox or in other VMs that do not support
+#      some advanced instruction sets.
+#      Used by STP only for now.
+#
+#
+
 S2ESRC:=$(CURDIR)/../s2e
 S2EBUILD:=$(CURDIR)
 

qemu/configure

@@ -981,6 +981,14 @@ case "$cpu" in
            ;;
 esac
 
+if [ "x$BUILD_ARCH" != "x" ]; then
+    CFLAGS="-march=$BUILD_ARCH $CFLAGS"
+    CXXFLAGS="-march=$BUILD_ARCH $CXXFLAGS"
+else
+    CFLAGS="-march=native $CFLAGS"
+    CXXFLAGS="-march=native $CXXFLAGS"
+fi
+
 if [ "x$address_sanitizer" = "xyes" ]; then
     CFLAGS="-fstack-protector-all -fsanitize=address $CFLAGS"
     CXXFLAGS="-fstack-protector-all -Wno-mismatched-tags -fsanitize=address $CXXFLAGS"

stp/scripts/Makefile.common

@@ -10,9 +10,10 @@
 
 -include $(TOP)/scripts/config.info
 
-# use -march=native if it works correctly (it's broken in GCC on OS X)
-ifeq ($(shell $(CXX) -march=native -E - < /dev/null >/dev/null 2>&1 && echo 1),1)
-    OPTIMIZE_MARCH_NATIVE = -march=native
+ifeq ($(BUILD_ARCH),)
+    OPTIMIZE_MARCH_NATIVE := -march=native
+else
+    OPTIMIZE_MARCH_NATIVE := -march=$(BUILD_ARCH)
 endif
 
 # Optimization