ScopedVariableAttribute¶
A scoped VOLATILE or ASYNCHRONOUS declaration for a host- or use-associated variable.
Declaration¶
Syntax¶
ScopedVariableAttribute(symbol_table parent_symtab, identifier name,
symbol variable, bool is_volatile, bool is_asynchronous)
Arguments¶
Argument |
Description |
|---|---|
|
the symbol table of the scope declaring the attributes. |
|
an internal symbol-table key, not a Fortran entity name. |
|
the visible host variable or its local ExternalSymbol, including a use rename. Following external symbols identifies the canonical Variable. |
|
the variable is VOLATILE in this scope. |
|
the variable is ASYNCHRONOUS in this scope. |
Return values¶
None.
Description¶
At least one attribute must be true. The reference must be visible from the declaring scope and identify a variable defined outside that scope. Attributes on a locally defined variable are recorded on that Variable instead. A later local declaration that shadows a host variable removes the tentative scoped declaration and attaches the attribute to the local variable.
This declaration changes neither the canonical entity nor other scopes that use it. It is not exported by USE or submodule imports. Its internal name must not appear in regenerated Fortran: the printer emits attribute statements using the visible variable name in the declaring specification part.
The reference describes entity identity, not a runtime access. Expression lowering must not replace it with a context-storage alias. Symbol duplication and template instantiation remap it to the corresponding entity in copied scopes, retaining shared host-module storage. Module serialization preserves the reference; verification checks visibility before external symbols are resolved, then checks the canonical variable after resolution.
Alias analysis and dead-store elimination must account for these scoped facts as well as the canonical variable’s attributes, including contained scopes.
Examples¶
In the following example, a remains an ordinary dummy outside the BLOCK;
the BLOCK’s specification part owns its ASYNCHRONOUS declaration.
subroutine scoped_roundtrip(a)
real :: a(4)
block
asynchronous :: a
a = 1
end block
end subroutine
program scoped_attributes
real :: a(4)
call scoped_roundtrip(a)
if (any(a /= 1)) error stop
end program
Its complete ASR is:
(TranslationUnit
:symtab (SymbolTable
:id 0
:symbols {
"scoped_attributes" (Program
:symtab (SymbolTable
:id 1
:symbols {
"a" (Variable
:parent_symtab 1
:name "a"
:dependencies []
:intent :Local
:symbolic_value nil
:value nil
:storage :Default
:type (Array
:type (Real
:kind 4
)
:dims [
(dimension
:start (IntegerConstant
:n 1
:type (Integer
:kind 4
)
:intboz_type :Decimal
)
:length (IntegerConstant
:n 4
:type (Integer
:kind 4
)
:intboz_type :Decimal
)
)
]
:physical_type :FixedSizeArray
:memory_space :Global
)
:type_declaration nil
:abi :Source
:access :Public
:presence :Required
:value_attr false
:target_attr false
:contiguous_attr false
:bindc_name nil
:is_volatile false
:is_asynchronous false
:is_protected false
:pass_attr :NotMethod
:self_argument nil
:codims []
:common_block nil
)
}
)
:name "scoped_attributes"
:dependencies []
:body [
(SubroutineCall
:name (SymbolRef 0 "scoped_roundtrip")
:original_name nil
:args [
(call_arg
:value (ArrayPhysicalCast
:arg (Var
:v (SymbolRef 1 "a")
)
:old :FixedSizeArray
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)
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)
:intboz_type :Decimal
)
:length (IntegerConstant
:n 4
:type (Integer
:kind 4
)
:intboz_type :Decimal
)
)
]
:physical_type :PointerArray
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)
:value nil
)
)
]
:dt nil
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)
(If
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(ArrayPhysicalCast
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)
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)
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)
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)
)
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)
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]
:physical_type :FixedSizeArray
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)
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)
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)
]
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)
"scoped_roundtrip" (Function
:symtab (SymbolTable
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"a" (Variable
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:name "a"
:dependencies []
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)
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)
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:length (IntegerConstant
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:type (Integer
:kind 4
)
:intboz_type :Decimal
)
)
]
:physical_type :PointerArray
:memory_space :Global
)
:type_declaration nil
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:access :Public
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:bindc_name nil
:is_volatile false
:is_asynchronous false
:is_protected false
:pass_attr :NotMethod
:self_argument nil
:codims []
:common_block nil
)
"block" (Block
:symtab (SymbolTable
:id 3
:symbols {
"__scoped_attribute_a" (ScopedVariableAttribute
:parent_symtab 3
:name "__scoped_attribute_a"
:variable (SymbolRef 2 "a")
:is_volatile false
:is_asynchronous true
)
}
)
:name "block"
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)
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)
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)
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)
]
)
}
)
:name "scoped_roundtrip"
:function_signature (FunctionType
:arg_types [
(Array
:type (Real
:kind 4
)
:dims [
(dimension
:start (IntegerConstant
:n 1
:type (Integer
:kind 4
)
:intboz_type :Decimal
)
:length (IntegerConstant
:n 4
:type (Integer
:kind 4
)
:intboz_type :Decimal
)
)
]
:physical_type :PointerArray
:memory_space :Global
)
]
:return_var_type nil
:abi :Source
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:elemental false
:pure false
:module false
:inline false
:static false
:restrictions []
:is_restriction false
:exec_space :Host
)
:dependencies []
:args [
(Var
:v (SymbolRef 2 "a")
)
]
:body [
(BlockCall
:label -1
:m (SymbolRef 2 "block")
)
]
:return_var nil
:access :Public
:deterministic true
:side_effect_free true
:module_file nil
)
}
)
:items []
:global_init nil
)