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-- Evaluation of static expressions.
-- Copyright (C) 2002, 2003, 2004, 2005 Tristan Gingold
--
-- GHDL is free software; you can redistribute it and/or modify it under
-- the terms of the GNU General Public License as published by the Free
-- Software Foundation; either version 2, or (at your option) any later
-- version.
--
-- GHDL is distributed in the hope that it will be useful, but WITHOUT ANY
-- WARRANTY; without even the implied warranty of MERCHANTABILITY or
-- FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
-- for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with GHDL; see the file COPYING. If not, write to the Free
-- Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-- 02111-1307, USA.
with Types; use Types;
with Iirs; use Iirs;
package Evaluation is
-- Evaluation is about compile-time computation of expressions, such as
-- 2 + 1 --> 3. This is (of course) possible only with locally (and some
-- globally) static expressions. Evaluation is required during semantic
-- analysis at many places (in fact those where locally static expression
-- are required by the language). For example, the type of O'Range (N)
-- depends on N, so we need to evaluate N.
--
-- The result of evaluation is a literal (integer, enumeration, real,
-- physical), a string or a simple aggregate. For scalar types, the
-- result is therefore normalized (there is only one kind of result), but
-- for array types, the result isn't: in general it will be a string, but
-- it may be a simple aggregate. Strings are preferred (because they are
-- more compact), but aren't possible in some cases. For example, the
-- evaluation of "Text" & NUL cannot be a string.
--
-- Some functions (like Eval_Static_Expr) simply returns a result (which
-- may be a node of the expression), others returns a result and set the
-- origin (Literal_Origin or Range_Origin) to remember the original
-- expression that was evaluation. The original expression is kept so that
-- it is possible to print the original tree.
-- Get the value of a physical integer literal or unit.
function Get_Physical_Value (Expr : Iir) return Iir_Int64;
-- Evaluate the locally static expression EXPR (without checking that EXPR
-- is locally static). Return a literal or an aggregate, without setting
-- the origin, and do not modify EXPR. This can be used only to get the
-- value of an expression, without replacing it.
function Eval_Static_Expr (Expr: Iir) return Iir;
-- Evaluate (ie compute) expression EXPR.
-- EXPR is required to be a locally static expression, otherwise an error
-- message is generated.
-- The result is a literal with the origin set.
function Eval_Expr (Expr: Iir) return Iir;
-- Same as Eval_Expr, but if EXPR is not locally static, the result is
-- EXPR. Also, if EXPR is null_iir, then null_iir is returned.
-- The purpose of this function is to evaluate an expression only if it
-- is locally static.
function Eval_Expr_If_Static (Expr : Iir) return Iir;
-- Evaluate a physical literal and return a normalized literal (using
-- the primary unit as unit).
function Eval_Physical_Literal (Expr : Iir) return Iir;
-- Return TRUE if literal EXPR is in SUB_TYPE bounds.
function Eval_Is_In_Bound (Expr : Iir; Sub_Type : Iir) return Boolean;
-- Emit an error if EXPR violates SUB_TYPE bounds.
procedure Eval_Check_Bound (Expr : Iir; Sub_Type : Iir);
-- Same as Eval_Expr, but a range check with SUB_TYPE is performed after
-- computation.
function Eval_Expr_Check (Expr : Iir; Sub_Type : Iir) return Iir;
-- Call Eval_Expr_Check only if EXPR is static.
function Eval_Expr_Check_If_Static (Expr : Iir; Atype : Iir) return Iir;
-- For a locally static range RNG (a range expression, a range attribute
-- or a name that denotes a type or a subtype) returns its corresponding
-- locally static range_expression. The bounds of the results are also
-- literals.
-- Return a range_expression or NULL_IIR for a non locally static range.
function Eval_Static_Range (Rng : Iir) return Iir;
-- Return a locally static range expression with the origin set for ARANGE.
function Eval_Range (Arange : Iir) return Iir;
-- If ARANGE is a locally static range, return locally static range
-- expression (with the origin set), else return ARANGE.
function Eval_Range_If_Static (Arange : Iir) return Iir;
-- Emit an error if A_RANGE is not included in SUB_TYPE. A_RANGE can be
-- a range expression, a range attribute or a name that denotes a discrete
-- type or subtype. A_RANGE must be a locally static range.
procedure Eval_Check_Range (A_Range : Iir; Sub_Type : Iir;
Any_Dir : Boolean);
-- Return TRUE if range expression A_RANGE is not included in SUB_TYPE.
function Eval_Is_Range_In_Bound
(A_Range : Iir; Sub_Type : Iir; Any_Dir : Boolean)
return Boolean;
-- Return TRUE iff VAL belongs to BOUND.
function Eval_Int_In_Range (Val : Iir_Int64; Bound : Iir) return Boolean;
-- Return the length of the discrete range CONSTRAINT.
function Eval_Discrete_Range_Length (Constraint : Iir) return Iir_Int64;
-- Return the length of SUB_TYPE.
function Eval_Discrete_Type_Length (Sub_Type : Iir) return Iir_Int64;
-- Get the left bound of a range constraint.
-- Note: the range constraint may be an attribute or a subtype.
function Eval_Discrete_Range_Left (Constraint : Iir) return Iir;
-- Return the position of EXPR, ie the result of sub_type'pos (EXPR), where
-- sub_type is the type of expr.
-- EXPR must be of a discrete subtype.
function Eval_Pos (Expr : Iir) return Iir_Int64;
-- Replace ORIGIN (an overflow literal) with extreme positive value (if
-- IS_POS is true) or extreme negative value.
function Build_Extreme_Value (Is_Pos : Boolean; Origin : Iir) return Iir;
-- Create an array subtype from LEN and BASE_TYPE, according to rules
-- of LRM93 7.3.2.2. (which are the same as LRM93 7.2.4).
function Create_Unidim_Array_By_Length
(Base_Type : Iir; Len : Iir_Int64; Loc : Iir)
return Iir_Array_Subtype_Definition;
-- Create a subtype of A_TYPE whose length is LEN.
-- This is used to create subtypes for strings or aggregates.
function Create_Range_Subtype_By_Length
(A_Type : Iir; Len : Iir_Int64; Loc : Location_Type)
return Iir;
-- Store into NAME_BUFFER, NAME_LENGTH the simple name, character literal
-- or operator sumbol of ID, using the same format as SIMPLE_NAME
-- attribute.
procedure Eval_Simple_Name (Id : Name_Id);
-- Compare two string literals (of same length).
type Compare_Type is (Compare_Lt, Compare_Eq, Compare_Gt);
function Compare_String_Literals (L, R : Iir) return Compare_Type;
-- Return the local part of 'Instance_Name or 'Path_Name.
type Path_Instance_Name_Type (Len : Natural) is record
-- The node before suffix (entity, architecture or generate iterator).
Path_Instance : Iir;
-- The suffix
Suffix : String (1 .. Len);
end record;
function Get_Path_Instance_Name_Suffix (Attr : Iir)
return Path_Instance_Name_Type;
end Evaluation;
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