diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index c4d0e36e9c0a2256f5dde1f4dc021c0328aa0cba..477dd007ea80272680751b61e35cc3eec79b66c3 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -19682,7 +19682,15 @@ ix86_can_change_mode_class (machine_mode from, machine_mode to,
 
   /* x87 registers can't do subreg at all, as all values are reformatted
      to extended precision.  */
-  if (MAYBE_FLOAT_CLASS_P (regclass))
+  if (MAYBE_FLOAT_CLASS_P (regclass)
+      && VALID_FP_MODE_P (from)
+      && VALID_FP_MODE_P (to))
+    return false;
+
+  /* Reject integer modes if the sizes aren't the same.  It would have
+     normally exited above.  */
+  if (MAYBE_FLOAT_CLASS_P (regclass)
+      && GET_MODE_SIZE (from) != GET_MODE_SIZE (to))
     return false;
 
   if (MAYBE_SSE_CLASS_P (regclass) || MAYBE_MMX_CLASS_P (regclass))