[patch]: Enhance rtl-dse to remove unaligned read after writes.

[Paolo Bonzini]

+      target = expand_binop (new_mode, lshr_optab, new_reg,
+			     GEN_INT (shift), new_reg, 1, OPTAB_DIRECT);
+
+      /* If the target is NULL, there was no way to do this, if the
+	 target is not equal to new_reg, then it had to add an extra
+	 move.  In either case, we fall back and try the arithmetic
+	 shift of this size to see if we get lucky there.  */
+      if (target != new_reg)
+	target = expand_binop (new_mode, ashr_optab, new_reg,
+			       GEN_INT (shift), new_reg, 1, OPTAB_DIRECT);

I guess you are missing and end_sequence/start_sequence pair to discard 
the result of expanding with lshr_optab.

Paolo