Index: testsuite/gcc.target/i386/pr45296.c
===================================================================
--- testsuite/gcc.target/i386/pr45296.c	(revision 0)
+++ testsuite/gcc.target/i386/pr45296.c	(revision 0)
@@ -0,0 +1 @@
+register long double F80 __asm__("st"); /* { dg-error "stack register" } */
Index: reginfo.c
===================================================================
--- reginfo.c	(revision 163291)
+++ reginfo.c	(working copy)
@@ -798,6 +798,14 @@ fix_register (const char *name, int fixe
 void
 globalize_reg (int i)
 {
+#ifdef STACK_REGS
+  if (IN_RANGE (i, FIRST_STACK_REG, LAST_STACK_REG))
+    {
+      error ("stack register used for global register variable");
+      return;
+    }
+#endif
+
   if (fixed_regs[i] == 0 && no_global_reg_vars)
     error ("global register variable follows a function definition");