New parser based on new version of the Coq backend of Menhir (#276)

What's new:

1. A rewrite of the Coq interpreter of Menhir automaton, with
   dependent types removing the need for runtime checks for the
   well-formedness of the LR stack. This seem to cause some speedup on
   the parsing time (~10% for lexing + parsing).

2. Thanks to 1., it is now possible to avoid the use of int31 for
   comparing symbols: Since this is only used for validation,
   positives are enough.

3. Speedup of Validation: on my machine, the time needed for compiling
   Parser.v goes from about 2 minutes to about 1 minute. This seem to
   be related to a performance bug in the completeness validator and
   to the use of positive instead of int31.

3. Menhir now generates a dedicated inductive type for
   (semantic-value-carrying) tokens (in addition to the already
   existing inductive type for (non-semantic-value-carrying)
   terminals. The end result is that the OCaml support code for the
   parser no longer contain calls to Obj.magic. The bad side of this
   change is that the formal specification of the parser is perhaps
   harder to read.

4. The parser and its library are now free of axioms (I used to use
   axiom K and proof irrelevance for easing proofs involving dependent
   types).

5. Use of a dedicated custom negative coinductive type for the input
   stream of tokens, instead of Coq stdlib's `Stream`. `Stream` is a
   positive coinductive type, which are now deprecated by Coq.

6. The fuel of the parser is now specified using its logarithm instead
   of its actual value. This makes it possible to give large fuel
   values instead of using the `let rec fuel = S fuel` hack.

7. Some refactoring in the lexer, the parser and the Cabs syntax tree.

The corresponding changes in Menhir have been released as part of
version 20190626. The `MenhirLib` directory is identical to the
content of the `src` directory of the corresponding `coq-menhirlib`
opam package except that:
   - In order to try to make CompCert compatible with several Menhir
     versions without updates, we do not check the version of menhir
     is compatible with the version of coq-menhirlib. Hence the
     `Version.v` file is not present in CompCert's copy.
   - Build-system related files have been removed.

1 files changed, 1 insertions, 11 deletions

diff --git a/extraction/extraction.v b/extraction/extraction.v
index c0286f7b..25319475 100644
--- a/extraction/extraction.v
+++ b/extraction/extraction.v
@@ -34,7 +34,6 @@ Require Clight.
 Require Compiler.
 Require Parser.
 Require Initializers.
-Require Int31.
 
 (* Standard lib *)
 Require Import ExtrOcamlBasic.
@@ -128,7 +127,7 @@ Extract Constant Compiler.time  => "Timing.time_coq".
 (*Extraction Inline Compiler.apply_total Compiler.apply_partial.*)
 
 (* Cabs *)
-Extract Constant Cabs.cabsloc =>
+Extract Constant Cabs.loc =>
 "{ lineno : int;
    filename: string;
    byteno: int;
@@ -137,15 +136,6 @@ Extract Constant Cabs.cabsloc =>
 Extract Inlined Constant Cabs.string => "String.t".
 Extract Constant Cabs.char_code => "int64".
 
-(* Int31 *)
-Extract Inductive Int31.digits => "bool" [ "false" "true" ].
-Extract Inductive Int31.int31 => "int" [ "Camlcoq.Int31.constr" ] "Camlcoq.Int31.destr".
-Extract Constant Int31.twice => "Camlcoq.Int31.twice".
-Extract Constant Int31.twice_plus_one => "Camlcoq.Int31.twice_plus_one".
-Extract Constant Int31.compare31 => "Camlcoq.Int31.compare".
-Extract Constant Int31.On => "0".
-Extract Constant Int31.In => "1".
-
 (* Processor-specific extraction directives *)
 
 Load extractionMachdep.