#define SET_GCT(to) gct = (to)
-#if defined(sparc_HOST_ARCH) || defined(i386_HOST_ARCH)
+#if defined(sparc_HOST_ARCH) || (defined(i386_HOST_ARCH) && defined(linux_HOST_OS))
// Don't use REG_base or R1 for gct on SPARC because they're getting clobbered
// by something else. Not sure what yet. -- BL 2009/01/03
-// Using __thread is better than stealing a register on x86, because
+// Using __thread is better than stealing a register on x86/Linux, because
// we have too few registers available. In my tests it was worth
// about 5% in GC performance, but of course that might change as gcc
// improves. -- SDM 2009/04/03