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Diffstat (limited to 'gcc-4.8.3/gcc/ada/exp_alfa.ads')
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1 files changed, 86 insertions, 0 deletions
diff --git a/gcc-4.8.3/gcc/ada/exp_alfa.ads b/gcc-4.8.3/gcc/ada/exp_alfa.ads new file mode 100644 index 000000000..7b67c8d3c --- /dev/null +++ b/gcc-4.8.3/gcc/ada/exp_alfa.ads @@ -0,0 +1,86 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- E X P _ A L F A -- +-- -- +-- S p e c -- +-- -- +-- Copyright (C) 2011-2012, Free Software Foundation, Inc. -- +-- -- +-- GNAT is free software; you can redistribute it and/or modify it under -- +-- terms of the GNU General Public License as published by the Free Soft- -- +-- ware Foundation; either version 3, or (at your option) any later ver- -- +-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- +-- OUT 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 distributed with GNAT; see file COPYING3. If not, go to -- +-- http://www.gnu.org/licenses for a complete copy of the license. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- Extensive contributions were provided by Ada Core Technologies Inc. -- +-- -- +------------------------------------------------------------------------------ + +-- This package implements a light expansion which is used in formal +-- verification mode (Alfa_Mode = True). Instead of a complete expansion +-- of nodes for code generation, this Alfa expansion targets generation +-- of intermediate code for formal verification. + +-- Expand_Alfa is called directly by Expander.Expand. + +-- Alfa expansion has three main objectives: + +-- 1. Perform limited expansion to explicit some Ada rules and constructs +-- (translate 'Old and 'Result, replace renamings by renamed, insert +-- conversions, expand actuals in calls to introduce temporaries, expand +-- generics instantiations) + +-- 2. Facilitate treatment for the formal verification back-end (fully +-- qualify names, expand set membership, compute data dependences) + +-- 3. Avoid the introduction of low-level code that is difficult to analyze +-- formally, as typically done in the full expansion for high-level +-- constructs (tasking, dispatching) + +-- To fulfill objective 1, Expand_Alfa selectively expands some constructs. + +-- To fulfill objective 2, the tree after Alfa expansion should be fully +-- analyzed semantically. In particular, all expression must have their proper +-- type, and semantic links should be set between tree nodes (partial to full +-- view, etc.) Some kinds of nodes should be either absent, or can be ignored +-- by the formal verification backend: + +-- N_Object_Renaming_Declaration: can be ignored safely +-- N_Expression_Function: absent (rewitten) +-- N_Expression_With_Actions: absent (not generated) + +-- Alfa cross-references are generated from the regular cross-references (used +-- for browsing and code understanding) and additional references collected +-- during semantic analysis, in particular on all dereferences. These Alfa +-- cross-references are output in a separate section of ALI files, as +-- described in alfa.adb. They are the basis for the computation of data +-- dependences in the formal verification backend. This implies that all +-- cross-references should be generated in this mode, even those that would +-- not make sense from a user point-of-view, and that cross-references that do +-- not lead to data dependences for subprograms can be safely ignored. + +-- To support the formal verification of units parameterized by data, the +-- value of deferred constants should not be considered as a compile-time +-- constant at program locations where the full view is not visible. + +-- To fulfill objective 3, Expand_Alfa does not expand features that are not +-- formally analyzed (tasking), or for which formal analysis relies on the +-- source level representation (dispatching, aspects, pragmas). However, these +-- should be semantically analyzed, which sometimes requires the insertion of +-- semantic pre-analysis, for example for subprogram contracts and pragma +-- check/assert. + +with Types; use Types; + +package Exp_Alfa is + + procedure Expand_Alfa (N : Node_Id); + +end Exp_Alfa; |