#include "flags.h"
#include "rtl.h"
#include "tm_p.h"
+#include "target.h"
#include "ggc.h"
#include "langhooks.h"
#include "hard-reg-set.h"
redirect_edge_var_map_destroy ();
}
-/* Helper function for useless_type_conversion_p. */
+/* Return true if the conversion from INNER_TYPE to OUTER_TYPE is a
+ useless type conversion, otherwise return false.
-static bool
-useless_type_conversion_p_1 (tree outer_type, tree inner_type)
+ This function implicitly defines the middle-end type system. With
+ the notion of 'a < b' meaning that useless_type_conversion_p (a, b)
+ holds and 'a > b' meaning that useless_type_conversion_p (b, a) holds,
+ the following invariants shall be fulfilled:
+
+ 1) useless_type_conversion_p is transitive.
+ If a < b and b < c then a < c.
+
+ 2) useless_type_conversion_p is not symmetric.
+ From a < b does not follow a > b.
+
+ 3) Types define the available set of operations applicable to values.
+ A type conversion is useless if the operations for the target type
+ is a subset of the operations for the source type. For example
+ casts to void* are useless, casts from void* are not (void* can't
+ be dereferenced or offsetted, but copied, hence its set of operations
+ is a strict subset of that of all other data pointer types). Casts
+ to const T* are useless (can't be written to), casts from const T*
+ to T* are not. */
+
+bool
+useless_type_conversion_p (tree outer_type, tree inner_type)
{
/* Do the following before stripping toplevel qualifiers. */
if (POINTER_TYPE_P (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
else if (POINTER_TYPE_P (inner_type)
&& POINTER_TYPE_P (outer_type))
{
+ /* If the outer type is (void *) or a pointer to an incomplete
+ record type, then the conversion is not necessary. */
+ if (VOID_TYPE_P (TREE_TYPE (outer_type))
+ || (AGGREGATE_TYPE_P (TREE_TYPE (outer_type))
+ && TREE_CODE (TREE_TYPE (outer_type)) != ARRAY_TYPE
+ && (TREE_CODE (TREE_TYPE (outer_type))
+ == TREE_CODE (TREE_TYPE (inner_type)))
+ && !COMPLETE_TYPE_P (TREE_TYPE (outer_type))))
+ return true;
+
/* Don't lose casts between pointers to volatile and non-volatile
qualified types. Doing so would result in changing the semantics
of later accesses. For function types the volatile qualifier
&& 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))
/* Otherwise pointers/references are equivalent if their pointed
to types are effectively the same. We can strip qualifiers
on pointed-to types for further comparison, which is done in
- the callee. */
- return useless_type_conversion_p_1 (TREE_TYPE (outer_type),
- TREE_TYPE (inner_type));
+ the callee. Note we have to use true compatibility here
+ because addresses are subject to propagation into dereferences
+ and thus might get the original type exposed which is equivalent
+ to a reverse conversion. */
+ return types_compatible_p (TREE_TYPE (outer_type),
+ TREE_TYPE (inner_type));
}
/* Recurse for complex types. */
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;
- /* ??? This seems to be necessary even for aggregates that don't
- have TYPE_STRUCTURAL_EQUALITY_P set. */
+ /* 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;
+ }
- /* ??? This should eventually just return false. */
- return lang_hooks.types_compatible_p (inner_type, outer_type);
+ /* Recurse on the element check. */
+ return useless_type_conversion_p (TREE_TYPE (outer_type),
+ TREE_TYPE (inner_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;
-}
-/* Return true if the conversion from INNER_TYPE to OUTER_TYPE is a
- useless type conversion, otherwise return false.
+ 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;
- This function implicitly defines the middle-end type system. With
- the notion of 'a < b' meaning that useless_type_conversion_p (a, b)
- holds and 'a > b' meaning that useless_type_conversion_p (b, a) holds,
- the following invariants shall be fulfilled:
+ /* If the return types are not compatible bail out. */
+ if (!useless_type_conversion_p (TREE_TYPE (outer_type),
+ TREE_TYPE (inner_type)))
+ return false;
- 1) useless_type_conversion_p is transitive.
- If a < b and b < c then a < c.
+ /* 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;
- 2) useless_type_conversion_p is not symmetric.
- From a < b does not follow a > b.
+ /* 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;
- 3) Types define the available set of operations applicable to values.
- A type conversion is useless if the operations for the target type
- is a subset of the operations for the source type. For example
- casts to void* are useless, casts from void* are not (void* can't
- be dereferenced or offsetted, but copied, hence its set of operations
- is a strict subset of that of all other data pointer types). Casts
- to const T* are useless (can't be written to), casts from const T*
- to T* are not. */
+ /* 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;
-bool
-useless_type_conversion_p (tree outer_type, tree inner_type)
-{
- /* If the outer type is (void *) or a pointer to an incomplete record type,
- then the conversion is not necessary.
- We have to make sure to not apply this while recursing though. */
- if (POINTER_TYPE_P (inner_type)
- && POINTER_TYPE_P (outer_type)
- && (VOID_TYPE_P (TREE_TYPE (outer_type))
- || (AGGREGATE_TYPE_P (TREE_TYPE (outer_type))
- && TREE_CODE (TREE_TYPE (outer_type)) != ARRAY_TYPE
- && (TREE_CODE (TREE_TYPE (outer_type))
- == TREE_CODE (TREE_TYPE (inner_type)))
- && !COMPLETE_TYPE_P (TREE_TYPE (outer_type)))))
- return true;
+ return true;
+ }
- return useless_type_conversion_p_1 (outer_type, inner_type);
+ /* 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))
+ {
+ if (TYPE_STRUCTURAL_EQUALITY_P (outer_type)
+ || TYPE_STRUCTURAL_EQUALITY_P (inner_type))
+ return lang_hooks.types_compatible_p (inner_type, outer_type);
+
+ return false;
+ }
+
+ return false;
}
/* Return true if a conversion from either type of TYPE1 and TYPE2
/* We do not care about LHS. */
if (wi->is_lhs)
- return NULL_TREE;
+ {
+ /* Except for operands of INDIRECT_REF. */
+ if (!INDIRECT_REF_P (t))
+ return NULL_TREE;
+ t = TREE_OPERAND (t, 0);
+ }
switch (TREE_CODE (t))
{
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