tree-ssa.c (useless_type_conversion_p_1): Make function and array type comparisons frontend independent.

2009-08-06  Richard Guenther  <rguenther@suse.de>

	* tree-ssa.c (useless_type_conversion_p_1): Make function and
	array type comparisons frontend independent.
	* Makefile.in (tree-ssa.o): Add $(TARGET_H) dependency.
	* tree-ssa-sccvn.c (copy_reference_ops_from_ref): Always fill
	out array reference lower bound and element size operands.
	(ao_ref_init_from_vn_reference): Properly compute the offset
	for ARRAY_RANGE_REF.
	(vn_reference_fold_indirect): Fill out array reference lower
	bound and element size operands.
	* tree-ssa-pre.c (phi_translate_1): Fail if we have to translate
	a non gimple valued reference operand which can happen for
	array reference lower bound or element size.
	(create_component_ref_by_pieces_1): Properly generate the
	element size operand for array references.

From-SVN: r150519

1 files changed, 119 insertions, 15 deletions

diff --git a/gcc/tree-ssa.c b/gcc/tree-ssa.c
index 28da94b..0b4cc96 100644
--- a/gcc/tree-ssa.c
+++ b/gcc/tree-ssa.c
@@ -26,6 +26,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "flags.h"
 #include "rtl.h"
 #include "tm_p.h"
+#include "target.h"
 #include "ggc.h"
 #include "langhooks.h"
 #include "hard-reg-set.h"
@@ -871,8 +872,10 @@ useless_type_conversion_p_1 (tree outer_type, tree inner_type)
       && TYPE_CANONICAL (inner_type) == TYPE_CANONICAL (outer_type))
     return true;
 
-  /* Changes in machine mode are never useless conversions.  */
-  if (TYPE_MODE (inner_type) != TYPE_MODE (outer_type))
+  /* Changes in machine mode are never useless conversions unless we
+     deal with aggregate types in which case we defer to later checks.  */
+  if (TYPE_MODE (inner_type) != TYPE_MODE (outer_type)
+      && !AGGREGATE_TYPE_P (inner_type))
     return false;
 
   /* If both the inner and outer types are integral types, then the
@@ -919,6 +922,11 @@ useless_type_conversion_p_1 (tree outer_type, tree inner_type)
 	  && TYPE_VOLATILE (TREE_TYPE (outer_type)))
 	return false;
 
+      /* We require explicit conversions from incomplete target types.  */
+      if (!COMPLETE_TYPE_P (TREE_TYPE (inner_type))
+	  && COMPLETE_TYPE_P (TREE_TYPE (outer_type)))
+	return false;
+
       /* Do not lose casts between pointers that when dereferenced access
 	 memory with different alias sets.  */
       if (get_deref_alias_set (inner_type) != get_deref_alias_set (outer_type))
@@ -948,33 +956,129 @@ useless_type_conversion_p_1 (tree outer_type, tree inner_type)
     return useless_type_conversion_p (TREE_TYPE (outer_type),
 				      TREE_TYPE (inner_type));
 
-  /* For aggregates we may need to fall back to structural equality
-     checks.  */
-  else if (AGGREGATE_TYPE_P (inner_type)
-	   && AGGREGATE_TYPE_P (outer_type))
+  else if (TREE_CODE (inner_type) == ARRAY_TYPE
+	   && TREE_CODE (outer_type) == ARRAY_TYPE)
     {
-      /* Different types of aggregates are incompatible.  */
-      if (TREE_CODE (inner_type) != TREE_CODE (outer_type))
+      /* Preserve string attributes.  */
+      if (TYPE_STRING_FLAG (inner_type) != TYPE_STRING_FLAG (outer_type))
 	return false;
 
       /* Conversions from array types with unknown extent to
 	 array types with known extent are not useless.  */
-      if (TREE_CODE (inner_type) == ARRAY_TYPE
-	  && !TYPE_DOMAIN (inner_type)
+      if (!TYPE_DOMAIN (inner_type)
 	  && TYPE_DOMAIN (outer_type))
 	return false;
 
+      /* Nor are conversions from array types with non-constant size to
+         array types with constant size or to different size.  */
+      if (TYPE_SIZE (outer_type)
+	  && TREE_CODE (TYPE_SIZE (outer_type)) == INTEGER_CST
+	  && (!TYPE_SIZE (inner_type)
+	      || TREE_CODE (TYPE_SIZE (inner_type)) != INTEGER_CST
+	      || !tree_int_cst_equal (TYPE_SIZE (outer_type),
+				      TYPE_SIZE (inner_type))))
+	return false;
+
+      /* Check conversions between arrays with partially known extents.
+	 If the array min/max values are constant they have to match.
+	 Otherwise allow conversions to unknown and variable extents.
+	 In particular this declares conversions that may change the
+	 mode to BLKmode as useless.  */
+      if (TYPE_DOMAIN (inner_type)
+	  && TYPE_DOMAIN (outer_type)
+	  && TYPE_DOMAIN (inner_type) != TYPE_DOMAIN (outer_type))
+	{
+	  tree inner_min = TYPE_MIN_VALUE (TYPE_DOMAIN (inner_type));
+	  tree outer_min = TYPE_MIN_VALUE (TYPE_DOMAIN (outer_type));
+	  tree inner_max = TYPE_MAX_VALUE (TYPE_DOMAIN (inner_type));
+	  tree outer_max = TYPE_MAX_VALUE (TYPE_DOMAIN (outer_type));
+
+	  /* After gimplification a variable min/max value carries no
+	     additional information compared to a NULL value.  All that
+	     matters has been lowered to be part of the IL.  */
+	  if (inner_min && TREE_CODE (inner_min) != INTEGER_CST)
+	    inner_min = NULL_TREE;
+	  if (outer_min && TREE_CODE (outer_min) != INTEGER_CST)
+	    outer_min = NULL_TREE;
+	  if (inner_max && TREE_CODE (inner_max) != INTEGER_CST)
+	    inner_max = NULL_TREE;
+	  if (outer_max && TREE_CODE (outer_max) != INTEGER_CST)
+	    outer_max = NULL_TREE;
+
+	  /* Conversions NULL / variable <- cst are useless, but not
+	     the other way around.  */
+	  if (outer_min
+	      && (!inner_min
+		  || !tree_int_cst_equal (inner_min, outer_min)))
+	    return false;
+	  if (outer_max
+	      && (!inner_max
+		  || !tree_int_cst_equal (inner_max, outer_max)))
+	    return false;
+	}
+
+      /* Recurse on the element check.  */
+      return useless_type_conversion_p (TREE_TYPE (outer_type),
+					TREE_TYPE (inner_type));
+    }
+
+  else if ((TREE_CODE (inner_type) == FUNCTION_TYPE
+	    || TREE_CODE (inner_type) == METHOD_TYPE)
+	   && TREE_CODE (inner_type) == TREE_CODE (outer_type))
+    {
+      tree outer_parm, inner_parm;
+
+      /* If the return types are not compatible bail out.  */
+      if (!useless_type_conversion_p (TREE_TYPE (outer_type),
+				      TREE_TYPE (inner_type)))
+	return false;
+
+      /* Method types should belong to a compatible base class.  */
+      if (TREE_CODE (inner_type) == METHOD_TYPE
+	  && !useless_type_conversion_p (TYPE_METHOD_BASETYPE (outer_type),
+					 TYPE_METHOD_BASETYPE (inner_type)))
+	return false;
+
+      /* A conversion to an unprototyped argument list is ok.  */
+      if (!TYPE_ARG_TYPES (outer_type))
+	return true;
+
+      /* If the argument types are compatible the conversion is useless.  */
+      if (TYPE_ARG_TYPES (outer_type) == TYPE_ARG_TYPES (inner_type))
+	return true;
+
+      for (outer_parm = TYPE_ARG_TYPES (outer_type),
+	   inner_parm = TYPE_ARG_TYPES (inner_type);
+	   outer_parm && inner_parm;
+	   outer_parm = TREE_CHAIN (outer_parm),
+	   inner_parm = TREE_CHAIN (inner_parm))
+	if (!useless_type_conversion_p (TREE_VALUE (outer_parm),
+					TREE_VALUE (inner_parm)))
+	  return false;
+
+      /* If there is a mismatch in the number of arguments the functions
+	 are not compatible.  */
+      if (outer_parm || inner_parm)
+	return false;
+
+      /* Defer to the target if necessary.  */
+      if (TYPE_ATTRIBUTES (inner_type) || TYPE_ATTRIBUTES (outer_type))
+	return targetm.comp_type_attributes (outer_type, inner_type) != 0;
+
+      return true;
+    }
+
+  /* For aggregates we may need to fall back to structural equality
+     checks.  */
+  else if (AGGREGATE_TYPE_P (inner_type)
+	   && TREE_CODE (inner_type) == TREE_CODE (outer_type))
+    {
       /* ???  This seems to be necessary even for aggregates that don't
 	 have TYPE_STRUCTURAL_EQUALITY_P set.  */
 
       /* ???  This should eventually just return false.  */
       return lang_hooks.types_compatible_p (inner_type, outer_type);
     }
-  /* Also for functions and possibly other types with
-     TYPE_STRUCTURAL_EQUALITY_P set.  */
-  else if (TYPE_STRUCTURAL_EQUALITY_P (inner_type)
-	   && TYPE_STRUCTURAL_EQUALITY_P (outer_type))
-    return lang_hooks.types_compatible_p (inner_type, outer_type);
   
   return false;
 }