forwprop: Pattern recognize more rotates [PR94344]

The following patch adjusts simplify_rotate to recognize more rotates,
basically we allow even some same precision integral -> integral
conversions, with the requirement that the RSHIFT_EXPR operand has to be
done in unsigned type (i.e. logical right shift), so that we compensate for
the combiner no longer being able to simplify those into rotates on some
targets.

2020-03-31  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/94344
	* tree-ssa-forwprop.c (simplify_rotate): Handle also same precision
	conversions, either on both operands of |^+ or just one.  Handle
	also extra same precision conversion on RSHIFT_EXPR first operand
	provided RSHIFT_EXPR is performed in unsigned type.

	* gcc.dg/pr94344.c: New test.

1 files changed, 44 insertions, 4 deletions

diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
index 234c1f7..e7eaa18 100644
--- a/gcc/tree-ssa-forwprop.c
+++ b/gcc/tree-ssa-forwprop.c
@@ -1562,14 +1562,14 @@ simplify_rotate (gimple_stmt_iterator *gsi)
   for (i = 0; i < 2; i++)
     defcodefor_name (arg[i], &def_code[i], &def_arg1[i], &def_arg2[i]);
 
-  /* Look through narrowing conversions.  */
+  /* Look through narrowing (or same precision) conversions.  */
   if (CONVERT_EXPR_CODE_P (def_code[0])
       && CONVERT_EXPR_CODE_P (def_code[1])
       && INTEGRAL_TYPE_P (TREE_TYPE (def_arg1[0]))
       && INTEGRAL_TYPE_P (TREE_TYPE (def_arg1[1]))
       && TYPE_PRECISION (TREE_TYPE (def_arg1[0]))
 	 == TYPE_PRECISION (TREE_TYPE (def_arg1[1]))
-      && TYPE_PRECISION (TREE_TYPE (def_arg1[0])) > TYPE_PRECISION (rtype)
+      && TYPE_PRECISION (TREE_TYPE (def_arg1[0])) >= TYPE_PRECISION (rtype)
       && has_single_use (arg[0])
       && has_single_use (arg[1]))
     {
@@ -1579,6 +1579,21 @@ simplify_rotate (gimple_stmt_iterator *gsi)
 	  defcodefor_name (arg[i], &def_code[i], &def_arg1[i], &def_arg2[i]);
 	}
     }
+  else
+    {
+      /* Handle signed rotate; the RSHIFT_EXPR has to be done
+	 in unsigned type but LSHIFT_EXPR could be signed.  */
+      i = (def_code[0] == LSHIFT_EXPR || def_code[0] == RSHIFT_EXPR);
+      if (CONVERT_EXPR_CODE_P (def_code[i])
+	  && (def_code[1 - i] == LSHIFT_EXPR || def_code[1 - i] == RSHIFT_EXPR)
+	  && INTEGRAL_TYPE_P (TREE_TYPE (def_arg1[i]))
+	  && TYPE_PRECISION (rtype) == TYPE_PRECISION (TREE_TYPE (def_arg1[i]))
+	  && has_single_use (arg[i]))
+	{
+	  arg[i] = def_arg1[i];
+	  defcodefor_name (arg[i], &def_code[i], &def_arg1[i], &def_arg2[i]);
+	}
+    }
 
   /* One operand has to be LSHIFT_EXPR and one RSHIFT_EXPR.  */
   for (i = 0; i < 2; i++)
@@ -1608,8 +1623,33 @@ simplify_rotate (gimple_stmt_iterator *gsi)
   if (!operand_equal_for_phi_arg_p (def_arg1[0], def_arg1[1])
       || !types_compatible_p (TREE_TYPE (def_arg1[0]),
 			      TREE_TYPE (def_arg1[1])))
-    return false;
-  if (!TYPE_UNSIGNED (TREE_TYPE (def_arg1[0])))
+    {
+      if ((TYPE_PRECISION (TREE_TYPE (def_arg1[0]))
+	   != TYPE_PRECISION (TREE_TYPE (def_arg1[1])))
+	  || (TYPE_UNSIGNED (TREE_TYPE (def_arg1[0]))
+	      == TYPE_UNSIGNED (TREE_TYPE (def_arg1[1]))))
+	return false;
+
+      /* Handle signed rotate; the RSHIFT_EXPR has to be done
+	 in unsigned type but LSHIFT_EXPR could be signed.  */
+      i = def_code[0] != RSHIFT_EXPR;
+      if (!TYPE_UNSIGNED (TREE_TYPE (def_arg1[i])))
+	return false;
+
+      tree tem;
+      enum tree_code code;
+      defcodefor_name (def_arg1[i], &code, &tem, NULL);
+      if (!CONVERT_EXPR_CODE_P (code)
+	  || !INTEGRAL_TYPE_P (TREE_TYPE (tem))
+	  || TYPE_PRECISION (TREE_TYPE (tem)) != TYPE_PRECISION (rtype))
+	return false;
+      def_arg1[i] = tem;
+      if (!operand_equal_for_phi_arg_p (def_arg1[0], def_arg1[1])
+	  || !types_compatible_p (TREE_TYPE (def_arg1[0]),
+				  TREE_TYPE (def_arg1[1])))
+	return false;
+    }
+  else if (!TYPE_UNSIGNED (TREE_TYPE (def_arg1[0])))
     return false;
 
   /* CNT1 + CNT2 == B case above.  */