#define SET_GCT(to) gct = (to)
-#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
+
+#if (defined(i386_HOST_ARCH) && defined(linux_HOST_OS))
// 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
extern __thread gc_thread* gct;
#define DECLARE_GCT __thread gc_thread* gct;
+
+#elif defined(sparc_TARGET_ARCH)
+// On SPARC we can't pin gct to a register. Names like %l1 are just offsets
+// into the register window, which change on each function call.
+//
+// There are eight global (non-window) registers, but they're used for other purposes.
+// %g0 -- always zero
+// %g1 -- volatile over function calls, used by the linker
+// %g2-%g3 -- used as scratch regs by the C compiler (caller saves)
+// %g4 -- volatile over function calls, used by the linker
+// %g5-%g7 -- reserved by the OS
+
+extern __thread gc_thread* gct;
+#define DECLARE_GCT __thread gc_thread* gct;
+
+
#elif defined(REG_Base) && !defined(i386_HOST_ARCH)
// on i386, REG_Base is %ebx which is also used for PIC, so we don't
// want to steal it
GLOBAL_REG_DECL(gc_thread*, gct, REG_Base)
#define DECLARE_GCT /* nothing */
+
#elif defined(REG_R1)
GLOBAL_REG_DECL(gc_thread*, gct, REG_R1)
#define DECLARE_GCT /* nothing */
+
#elif defined(__GNUC__)
extern __thread gc_thread* gct;