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decl.c (gnat_to_gnu_entity): Create a mere scalar constant instead of a reference for renaming of scalar literal. 

* gcc-interface/decl.c (gnat_to_gnu_entity) <object>: Create a mere
	scalar constant instead of a reference for renaming of scalar literal.
	Do not create a new object for constant renaming except for a function
	call.  Make sure a VAR_DECL is created for the renaming pointer.
	* gcc-interface/trans.c (constant_decl_with_initializer_p): New.
	(fold_constant_decl_in_expr): New function.
	(Identifier_to_gnu): Use constant_decl_with_initializer_p.
	For a constant renaming, try to fold a constant DECL in the result.
	(lvalue_required_p) <N_Object_Renaming_Declaration>: Always return 1.
	(Identifier_to_gnu): Reference the renamed object of constant renaming
	pointers directly.
	(Case_Statement_to_gnu): Do not re-fold the bounds of integer types.
	Assert that the case values are constant.
	* gcc-interface/utils.c (invalidate_global_renaming_pointers): Do not
	invalidate constant renaming pointers.

Co-Authored-By: Pierre-Marie de Rodat <derodat@adacore.com>

From-SVN: r209411
This commit is contained in:
Eric Botcazou 2014-04-15 09:23:21 +00:00 committed by Eric Botcazou
parent e63b36bda5
commit e297e2eaa6
4 changed files with 199 additions and 123 deletions
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19
gcc/ada/ChangeLog
View File

@ -1,3 +1,22 @@
2014-04-15 Eric Botcazou <ebotcazou@adacore.com>
Pierre-Marie de Rodat <derodat@adacore.com>
* gcc-interface/decl.c (gnat_to_gnu_entity) <object>: Create a mere
scalar constant instead of a reference for renaming of scalar literal.
Do not create a new object for constant renaming except for a function
call. Make sure a VAR_DECL is created for the renaming pointer.
* gcc-interface/trans.c (constant_decl_with_initializer_p): New.
(fold_constant_decl_in_expr): New function.
(Identifier_to_gnu): Use constant_decl_with_initializer_p.
For a constant renaming, try to fold a constant DECL in the result.
(lvalue_required_p) <N_Object_Renaming_Declaration>: Always return 1.
(Identifier_to_gnu): Reference the renamed object of constant renaming
pointers directly.
(Case_Statement_to_gnu): Do not re-fold the bounds of integer types.
Assert that the case values are constant.
* gcc-interface/utils.c (invalidate_global_renaming_pointers): Do not
invalidate constant renaming pointers.
2014-04-15 Eric Botcazou <ebotcazou@adacore.com>
* gcc-interface/utils.c (type_for_vector_element_p): New predicate.

145
gcc/ada/gcc-interface/decl.c
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@ -960,18 +960,20 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, int definition)
gnu_type = TREE_TYPE (gnu_expr);
/* Case 1: If this is a constant renaming stemming from a function
call, treat it as a normal object whose initial value is what
is being renamed. RM 3.3 says that the result of evaluating a
function call is a constant object. As a consequence, it can
be the inner object of a constant renaming. In this case, the
renaming must be fully instantiated, i.e. it cannot be a mere
reference to (part of) an existing object. */
call, treat it as a normal object whose initial value is what is
being renamed. RM 3.3 says that the result of evaluating a
function call is a constant object. Treat constant literals
the same way. As a consequence, it can be the inner object of
a constant renaming. In this case, the renaming must be fully
instantiated, i.e. it cannot be a mere reference to (part of) an
existing object. */
if (const_flag)
{
tree inner_object = gnu_expr;
while (handled_component_p (inner_object))
inner_object = TREE_OPERAND (inner_object, 0);
if (TREE_CODE (inner_object) == CALL_EXPR)
if (TREE_CODE (inner_object) == CALL_EXPR
|| CONSTANT_CLASS_P (inner_object))
create_normal_object = true;
}
@ -1030,15 +1032,7 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, int definition)
about that failure. */
}
/* Case 3: If this is a constant renaming and creating a
new object is allowed and cheap, treat it as a normal
object whose initial value is what is being renamed. */
if (const_flag
&& !Is_Composite_Type
(Underlying_Type (Etype (gnat_entity))))
;
/* Case 4: Make this into a constant pointer to the object we
/* Case 3: Make this into a constant pointer to the object we
are to rename and attach the object to the pointer if it is
something we can stabilize.
@ -1050,68 +1044,59 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, int definition)
The pointer is called a "renaming" pointer in this case.
In the rare cases where we cannot stabilize the renamed
object, we just make a "bare" pointer, and the renamed
entity is always accessed indirectly through it. */
else
object, we just make a "bare" pointer and the renamed
object will always be accessed indirectly through it.
Note that we need to preserve the volatility of the renamed
object through the indirection. */
if (TREE_THIS_VOLATILE (gnu_expr) && !TYPE_VOLATILE (gnu_type))
gnu_type = build_qualified_type (gnu_type,
(TYPE_QUALS (gnu_type)
| TYPE_QUAL_VOLATILE));
gnu_type = build_reference_type (gnu_type);
inner_const_flag = TREE_READONLY (gnu_expr);
const_flag = true;
/* If the previous attempt at stabilizing failed, there is
no point in trying again and we reuse the result without
attaching it to the pointer. In this case it will only
be used as the initializing expression of the pointer and
thus needs no special treatment with regard to multiple
evaluations.
Otherwise, try to stabilize and attach the expression to
the pointer if the stabilization succeeds.
Note that this might introduce SAVE_EXPRs and we don't
check whether we are at the global level or not. This
is fine since we are building a pointer initializer and
neither the pointer nor the initializing expression can
be accessed before the pointer elaboration has taken
place in a correct program.
These SAVE_EXPRs will be evaluated at the right place
by either the evaluation of the initializer for the
non-global case or the elaboration code for the global
case, and will be attached to the elaboration procedure
in the latter case. */
if (!maybe_stable_expr)
{
/* We need to preserve the volatileness of the renamed
object through the indirection. */
if (TREE_THIS_VOLATILE (gnu_expr)
&& !TYPE_VOLATILE (gnu_type))
gnu_type
= build_qualified_type (gnu_type,
(TYPE_QUALS (gnu_type)
| TYPE_QUAL_VOLATILE));
gnu_type = build_reference_type (gnu_type);
inner_const_flag = TREE_READONLY (gnu_expr);
const_flag = true;
maybe_stable_expr
= gnat_stabilize_reference (gnu_expr, true, &stable);
/* If the previous attempt at stabilizing failed, there
is no point in trying again and we reuse the result
without attaching it to the pointer. In this case it
will only be used as the initializing expression of
the pointer and thus needs no special treatment with
regard to multiple evaluations. */
if (maybe_stable_expr)
;
/* Otherwise, try to stabilize and attach the expression
to the pointer if the stabilization succeeds.
Note that this might introduce SAVE_EXPRs and we don't
check whether we're at the global level or not. This
is fine since we are building a pointer initializer and
neither the pointer nor the initializing expression can
be accessed before the pointer elaboration has taken
place in a correct program.
These SAVE_EXPRs will be evaluated at the right place
by either the evaluation of the initializer for the
non-global case or the elaboration code for the global
case, and will be attached to the elaboration procedure
in the latter case. */
else
{
maybe_stable_expr
= gnat_stabilize_reference (gnu_expr, true, &stable);
if (stable)
renamed_obj = maybe_stable_expr;
/* Attaching is actually performed downstream, as soon
as we have a VAR_DECL for the pointer we make. */
}
if (type_annotate_only
&& TREE_CODE (maybe_stable_expr) == ERROR_MARK)
gnu_expr = NULL_TREE;
else
gnu_expr = build_unary_op (ADDR_EXPR, gnu_type,
maybe_stable_expr);
gnu_size = NULL_TREE;
used_by_ref = true;
if (stable)
renamed_obj = maybe_stable_expr;
}
if (type_annotate_only
&& TREE_CODE (maybe_stable_expr) == ERROR_MARK)
gnu_expr = NULL_TREE;
else
gnu_expr
= build_unary_op (ADDR_EXPR, gnu_type, maybe_stable_expr);
gnu_size = NULL_TREE;
used_by_ref = true;
}
}
@ -1483,10 +1468,10 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, int definition)
/* Now create the variable or the constant and set various flags. */
gnu_decl
= create_var_decl (gnu_entity_name, gnu_ext_name, gnu_type,
gnu_expr, const_flag, Is_Public (gnat_entity),
imported_p || !definition, static_p, attr_list,
gnat_entity);
= create_var_decl_1 (gnu_entity_name, gnu_ext_name, gnu_type,
gnu_expr, const_flag, Is_Public (gnat_entity),
imported_p || !definition, static_p,
!renamed_obj, attr_list, gnat_entity);
DECL_BY_REF_P (gnu_decl) = used_by_ref;
DECL_POINTS_TO_READONLY_P (gnu_decl) = used_by_ref && inner_const_flag;
DECL_CAN_NEVER_BE_NULL_P (gnu_decl) = Can_Never_Be_Null (gnat_entity);
@ -1517,7 +1502,7 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, int definition)
/* If this is a renaming pointer, attach the renamed object to it and
register it if we are at the global level. Note that an external
constant is at the global level. */
if (TREE_CODE (gnu_decl) == VAR_DECL && renamed_obj)
if (renamed_obj)
{
SET_DECL_RENAMED_OBJECT (gnu_decl, renamed_obj);
if ((!definition && kind == E_Constant) || global_bindings_p ())

150
gcc/ada/gcc-interface/trans.c
View File

@ -898,17 +898,8 @@ lvalue_required_p (Node_Id gnat_node, tree gnu_type, bool constant,
address_of_constant, aliased);
case N_Object_Renaming_Declaration:
/* We need to make a real renaming only if the constant object is
aliased or if we may use a renaming pointer; otherwise we can
optimize and return the rvalue. We make an exception if the object
is an identifier since in this case the rvalue can be propagated
attached to the CONST_DECL. */
return (!constant
|| aliased
/* This should match the constant case of the renaming code. */
|| Is_Composite_Type
(Underlying_Type (Etype (Name (gnat_parent))))
|| Nkind (Name (gnat_parent)) == N_Identifier);
/* We need to preserve addresses through a renaming. */
return 1;
case N_Object_Declaration:
/* We cannot use a constructor if this is an atomic object because
@ -968,6 +959,77 @@ lvalue_required_p (Node_Id gnat_node, tree gnu_type, bool constant,
gcc_unreachable ();
}
/* Return true if T is a constant DECL node that can be safely replaced
by its initializer. */
static bool
constant_decl_with_initializer_p (tree t)
{
if (!TREE_CONSTANT (t) || !DECL_P (t) || !DECL_INITIAL (t))
return false;
/* Return false for aggregate types that contain a placeholder since
their initializers cannot be manipulated easily. */
if (AGGREGATE_TYPE_P (TREE_TYPE (t))
&& !TYPE_IS_FAT_POINTER_P (TREE_TYPE (t))
&& type_contains_placeholder_p (TREE_TYPE (t)))
return false;
return true;
}
/* Return an expression equivalent to EXP but where constant DECL nodes
have been replaced by their initializer. */
static tree
fold_constant_decl_in_expr (tree exp)
{
enum tree_code code = TREE_CODE (exp);
tree op0;
switch (code)
{
case CONST_DECL:
case VAR_DECL:
if (!constant_decl_with_initializer_p (exp))
return exp;
return DECL_INITIAL (exp);
case BIT_FIELD_REF:
case COMPONENT_REF:
op0 = fold_constant_decl_in_expr (TREE_OPERAND (exp, 0));
if (op0 == TREE_OPERAND (exp, 0))
return exp;
return fold_build3 (code, TREE_TYPE (exp), op0, TREE_OPERAND (exp, 1),
TREE_OPERAND (exp, 2));
case ARRAY_REF:
case ARRAY_RANGE_REF:
op0 = fold_constant_decl_in_expr (TREE_OPERAND (exp, 0));
if (op0 == TREE_OPERAND (exp, 0))
return exp;
return fold (build4 (code, TREE_TYPE (exp), op0, TREE_OPERAND (exp, 1),
TREE_OPERAND (exp, 2), TREE_OPERAND (exp, 3)));
case VIEW_CONVERT_EXPR:
case REALPART_EXPR:
case IMAGPART_EXPR:
op0 = fold_constant_decl_in_expr (TREE_OPERAND (exp, 0));
if (op0 == TREE_OPERAND (exp, 0))
return exp;
return fold_build1 (code, TREE_TYPE (exp), op0);
default:
return exp;
}
gcc_unreachable ();
}
/* Subroutine of gnat_to_gnu to translate gnat_node, an N_Identifier,
to a GCC tree, which is returned. GNU_RESULT_TYPE_P is a pointer
to where we should place the result type. */
@ -1112,13 +1174,16 @@ Identifier_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p)
true, false)))
gnu_result = DECL_INITIAL (gnu_result);
/* If it's a renaming pointer and we are at the right binding level,
we can reference the renamed object directly, since the renamed
expression has been protected against multiple evaluations. */
/* If it's a renaming pointer and, either the renamed object is constant
or we are at the right binding level, we can reference the renamed
object directly, since it is constant or has been protected against
multiple evaluations. */
if (TREE_CODE (gnu_result) == VAR_DECL
&& !DECL_LOOP_PARM_P (gnu_result)
&& DECL_RENAMED_OBJECT (gnu_result)
&& (!DECL_RENAMING_GLOBAL_P (gnu_result) || global_bindings_p ()))
&& (TREE_CONSTANT (DECL_RENAMED_OBJECT (gnu_result))
|| !DECL_RENAMING_GLOBAL_P (gnu_result)
|| global_bindings_p ()))
gnu_result = DECL_RENAMED_OBJECT (gnu_result);
/* Otherwise, do the final dereference. */
@ -1138,15 +1203,8 @@ Identifier_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p)
/* If we have a constant declaration and its initializer, try to return the
latter to avoid the need to call fold in lots of places and the need for
elaboration code if this identifier is used as an initializer itself.
Don't do it for aggregate types that contain a placeholder since their
initializers cannot be manipulated easily. */
if (TREE_CONSTANT (gnu_result)
&& DECL_P (gnu_result)
&& DECL_INITIAL (gnu_result)
&& !(AGGREGATE_TYPE_P (TREE_TYPE (gnu_result))
&& !TYPE_IS_FAT_POINTER_P (TREE_TYPE (gnu_result))
&& type_contains_placeholder_p (TREE_TYPE (gnu_result))))
elaboration code if this identifier is used as an initializer itself. */
if (constant_decl_with_initializer_p (gnu_result))
{
bool constant_only = (TREE_CODE (gnu_result) == CONST_DECL
&& !DECL_CONST_CORRESPONDING_VAR (gnu_result));
@ -1166,6 +1224,21 @@ Identifier_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p)
gnu_result = DECL_INITIAL (gnu_result);
}
/* But for a constant renaming we couldn't do that incrementally for its
definition because of the need to return an lvalue so, if the present
context doesn't itself require an lvalue, we try again here. */
else if (Ekind (gnat_temp) == E_Constant
&& Is_Elementary_Type (gnat_temp_type)
&& Present (Renamed_Object (gnat_temp)))
{
if (require_lvalue < 0)
require_lvalue
= lvalue_required_p (gnat_node, gnu_result_type, true, false,
Is_Aliased (gnat_temp));
if (!require_lvalue)
gnu_result = fold_constant_decl_in_expr (gnu_result);
}
/* The GNAT tree has the type of a function set to its result type, so we
adjust here. Also use the type of the result if the Etype is a subtype
that is nominally unconstrained. Likewise if this is a deferred constant
@ -2327,9 +2400,11 @@ Case_Statement_to_gnu (Node_Id gnat_node)
/* First compile all the different case choices for the current WHEN
alternative. */
for (gnat_choice = First (Discrete_Choices (gnat_when));
Present (gnat_choice); gnat_choice = Next (gnat_choice))
Present (gnat_choice);
gnat_choice = Next (gnat_choice))
{
tree gnu_low = NULL_TREE, gnu_high = NULL_TREE;
tree label = create_artificial_label (input_location);
switch (Nkind (gnat_choice))
{
@ -2353,8 +2428,8 @@ Case_Statement_to_gnu (Node_Id gnat_node)
{
tree gnu_type = get_unpadded_type (Entity (gnat_choice));
gnu_low = fold (TYPE_MIN_VALUE (gnu_type));
gnu_high = fold (TYPE_MAX_VALUE (gnu_type));
gnu_low = TYPE_MIN_VALUE (gnu_type);
gnu_high = TYPE_MAX_VALUE (gnu_type);
break;
}
@ -2372,20 +2447,13 @@ Case_Statement_to_gnu (Node_Id gnat_node)
gcc_unreachable ();
}
/* If the case value is a subtype that raises Constraint_Error at
run time because of a wrong bound, then gnu_low or gnu_high is
not translated into an INTEGER_CST. In such a case, we need
to ensure that the when statement is not added in the tree,
otherwise it will crash the gimplifier. */
if ((!gnu_low || TREE_CODE (gnu_low) == INTEGER_CST)
&& (!gnu_high || TREE_CODE (gnu_high) == INTEGER_CST))
{
add_stmt_with_node (build_case_label
(gnu_low, gnu_high,
create_artificial_label (input_location)),
gnat_choice);
choices_added_p = true;
}
/* Everything should be folded into constants at this point. */
gcc_assert (!gnu_low || TREE_CODE (gnu_low) == INTEGER_CST);
gcc_assert (!gnu_high || TREE_CODE (gnu_high) == INTEGER_CST);
add_stmt_with_node (build_case_label (gnu_low, gnu_high, label),
gnat_choice);
choices_added_p = true;
}
/* This construct doesn't define a scope so we shouldn't push a binding

8
gcc/ada/gcc-interface/utils.c
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@ -2514,7 +2514,10 @@ record_global_renaming_pointer (tree decl)
vec_safe_push (global_renaming_pointers, decl);
}
/* Invalidate the global renaming pointers. */
/* Invalidate the global renaming pointers that are not constant, lest their
renamed object contains SAVE_EXPRs tied to an elaboration routine. Note
that we should not blindly invalidate everything here because of the need
to propagate constant values through renaming. */
void
invalidate_global_renaming_pointers (void)
@ -2526,7 +2529,8 @@ invalidate_global_renaming_pointers (void)
return;
FOR_EACH_VEC_ELT (*global_renaming_pointers, i, iter)
SET_DECL_RENAMED_OBJECT (iter, NULL_TREE);
if (!TREE_CONSTANT (DECL_RENAMED_OBJECT (iter)))
SET_DECL_RENAMED_OBJECT (iter, NULL_TREE);
vec_free (global_renaming_pointers);
}