[PATCH 5/5] Remove CANNOT_CHANGE_MODE_CLASS workaround in i386.c

[Richard Sandiford]

Patch 4 should make it possible to relax i386'a CANNOT_CHANGE_MODE_CLASS,
solving the missed optimisation that triggered the original thread.


gcc/
        * config/i386/i386.c (ix86_cannot_change_mode_class): Remove
        GET_MODE_SIZE (to) < GET_MODE_SIZE (from) test.

Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c      2014-09-15 09:48:11.310438531 +0100
+++ gcc/config/i386/i386.c      2014-09-15 09:48:11.310438531 +0100
@@ -37526,13 +37526,6 @@ ix86_cannot_change_mode_class (enum mach
         the vec_dupv4hi pattern.  */
       if (GET_MODE_SIZE (from) < 4)
        return true;
-
-      /* Vector registers do not support subreg with nonzero offsets, which
-        are otherwise valid for integer registers.  Since we can't see
-        whether we have a nonzero offset from here, prohibit all
-         nonparadoxical subregs changing size.  */
-      if (GET_MODE_SIZE (to) < GET_MODE_SIZE (from))
-       return true;
     }
 
   return false;