[PATCH] Remove odd restriction on conversion folding

[Richard Biener]

The following removes the restriction of not removing a useless
intermediate conversion if the final conversion is to a type
whose precision doesn't match its mode precision (in case the
intermediate conversion has the same mode).

Possibly from the times where such outer conversion didn't generate
any code (IIRC I fixed that early during the 4.x series).

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2016-07-29  Richard Biener  <rguenther@suse.de>

	* match.pd ((T)(T2)x -> (T)x): Remove restriction on final
	precision not matching mode precision.

Index: gcc/match.pd
===================================================================
--- gcc/match.pd	(revision 237813)
+++ gcc/match.pd	(working copy)
@@ -1652,14 +1652,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        float or both integer, we don't need the middle conversion if the
        former is wider than the latter and doesn't change the signedness
        (for integers).  Avoid this if the final type is a pointer since
-       then we sometimes need the middle conversion.  Likewise if the
-       final type has a precision not equal to the size of its mode.  */
+       then we sometimes need the middle conversion.  */
     (if (((inter_int && inside_int) || (inter_float && inside_float))
 	 && (final_int || final_float)
 	 && inter_prec >= inside_prec
-	 && (inter_float || inter_unsignedp == inside_unsignedp)
-	 && ! (final_prec != GET_MODE_PRECISION (TYPE_MODE (type))
-	       && TYPE_MODE (type) == TYPE_MODE (inter_type)))
+	 && (inter_float || inter_unsignedp == inside_unsignedp))
      (ocvt @0))
 
     /* If we have a sign-extension of a zero-extended value, we can
@@ -1692,9 +1689,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 	 && ((inter_unsignedp && inter_prec > inside_prec)
 	     == (final_unsignedp && final_prec > inter_prec))
 	 && ! (inside_ptr && inter_prec != final_prec)
-	 && ! (final_ptr && inside_prec != inter_prec)
-	 && ! (final_prec != GET_MODE_PRECISION (TYPE_MODE (type))
-	       && TYPE_MODE (type) == TYPE_MODE (inter_type)))
+	 && ! (final_ptr && inside_prec != inter_prec))
      (ocvt @0))
 
     /* A truncation to an unsigned type (a zero-extension) should be