https://git.altlinux.org/srpms/p/potrace.git?p=potrace.git;a=commitdiff;h=385f40d2d9827049f5f43f73d05e9fc7472e0da4
https://bugs.gentoo.org/868465
--- a/configure.ac
+++ b/configure.ac
@@ -251,9 +251,10 @@ AC_CHECK_FUNC(strncasecmp, ,
 dnl ----------------------------------------------------------------------
 dnl Check whether we have i386 features
 AC_MSG_CHECKING([for Intel 386])
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[int x;
-  asm("bsf %1,%0\njnz 0f\nmovl $32,%0\n0:":"=r"(x):"r"(x));
-  return x; /* need this so that -O2 does not optimize the asm away */
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[int x = 1;
+  volatile asm("bsf %1,%0\njnz 0f\nmovl $32,%0\n0:":"=r"(x):"r"(x):"memory");
+  /* volatile and "memory" clobber ensures '-O2 -flto' does not optimize the asm away */
+  return x;
 ]])],[AC_MSG_RESULT(yes) 
  AC_DEFINE(HAVE_I386,, Can we use Intel 386 optimizations?)
 ],[AC_MSG_RESULT(no)])