X-Git-Url: https://git.xandkar.net/?p=tiger.ml.git;a=blobdiff_plain;f=README.md;h=0678fa9ca0f505c0a5dcd3311ad1e45d67c32d08;hp=632225a4993760aab5a0c0515b84058539f83858;hb=299dd05453cc3ce02261fe3f224d9f19a28ec551;hpb=96ad2fee9c1cde8e8ab49c2589b381ad5a4a750e

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 Tiger.ml
 ========
+A Tiger-compiler implementation in (OCa)ML
 
-Project Plan
-------------
-
-I. Fundamentals of Compilation
-    1. Introduction
-    2. Lexical Analysis
-    3. Parsing
-    4. Abstract Syntax
-    5. Semantic Analysis
-    6. Activation Records
-    7. Translation to Intermediate Code
-    8. Basic Blocks and Traces
-    9. Instruction Selection
-    10. Liveness Analysis
-    11. Register Allocation
-    12. Putting It
-II. Advanced Topics
-    13. Garbage Collection
-    14. Object-Oriented Languages
-    15. Functional Programming Languages
-    16. Polymorphic Types
-    17. Dataflow Analysis
-    18. Loop Optimizations
-    19. Static Single-Assignment Form
-    20. Pipelining and Scheduling
-    21. The Memory Hierarchy
+Status
+------
+
+![screenshot-tests-head](screenshots/tests-head.jpg)
+...
+![screenshot-tests-tail](screenshots/tests-tail.jpg)
+
+### Features
+#### Done
+- [x] ch 1: Warm-up AST
+- [x] ch 2: Lexer
+- [x] ch 3: Parser
+- [x] ch 4: AST
+- [x] ch 5: Semantic Analysis (type checking)
+#### In-progress
+- [ ] ch 6: Activation Records
+#### TODO (short-term)
+- [ ] ch 7: Translation to Intermediate Code
+- [ ] ch 08: Basic Blocks and Traces
+- [ ] ch 09: Instruction Selection
+- [ ] ch 10: Liveness Analysis
+- [ ] ch 11: Register Allocation
+- [ ] ch 12: Putting It All Together
+#### TODO (long-term)
+- [ ] ch 13: Garbage Collection
+- [ ] ch 15: Functional Programming Languages
+- [ ] ch 16: Polymorphic Types
+- [ ] ch 17: Dataflow Analysis
+- [ ] ch 18: Loop Optimizations
+- [ ] ch 19: Static Single-Assignment Form
+- [ ] ch 20: Pipelining and Scheduling
+- [ ] ch 21: The Memory Hierarchy
+#### Maybe
+- [ ] ch 14: Object-Oriented Languages
+
+### Technical issues
+- [-] testing framework
+  - [x] run arbitrary code snippets
+  - [x] check non-failures
+  - [x] check expected output
+  - [-] check expected exceptions
+    - [x] semant stage
+    - [ ] generalized expect `Output ('a option) | Exception of (exn -> bool)`
+  - [x] run all book test case files 
+  - [-] grid view (cols: lex, pars, semant, etc.; rows: test cases.) 
+    - [x] implementation
+    - [ ] refactoring
+  - [ ] test time-outs (motive: cycle non-detection caused an infinite loop)
+    - [ ] parallel test execution
+- [ ] Travis CI
+
+Implementation Notes
+--------------------
+
+### Parser
+
+#### shift/reduce conflicts
+##### grouping consecutive declarations
+In order to support mutual recursion, we need to group consecutive
+type and function declarations (see Tiger-book pages 97-99).
+
+Initially, I defined the rules to do so as:
+
+    decs:
+      | dec      { $1 :: [] }
+      | dec decs { $1 :: $2 }
+      ;
+    dec:
+      | var_dec  { $1 }
+      | typ_decs { Ast.TypeDecs $1 }
+      | fun_decs { Ast.FunDecs $1 }
+      ;
+
+which, while straightforward (and working, because `ocamlyacc` defaults to
+shift in case of a conflict), nonetheless caused a shift/reduce conflict in
+each of: `typ_decs` and `fun_decs`; where the parser did not know whether to
+shift and stay in `(typ|fun_)_dec` state or to reduce and get back to `dec`
+state.
+
+Sadly, tagging the rules with a lower precedence (to explicitly favor
+shifting) - does not help :(
+
+    %nonassoc LOWEST
+    ...
+    dec:
+      | var_dec                { $1 }
+      | typ_decs  %prec LOWEST { Ast.TypeDecs $1 }
+      | fun_decs  %prec LOWEST { Ast.FunDecs $1 }
+      ;
+
+The difficulty seems to be in the lack of a separator token which would be
+able to definitively mark the end of each sequence of consecutive
+`(typ_|fun_)` declarations.
+
+Keeping this in mind, another alternative is to manually capture the possible
+interspersion patterns in the rules like:
+
+    (N * foo) followed-by (N * not-foo)
+
+for the exception of `var_dec`, which, since we do not need to group its
+consecutive sequences, can be reduced upon first sighting.
+
+##### lval
+
+### AST
+
+#### print as M-exp
+
+I chose to pretty-print AST as an (indented)
+[M-expression](https://en.wikipedia.org/wiki/M-expression) - an underrated
+format, used in Mathematica and was intended for Lisp by McCarthy himself; it
+is nearly as flexible as S-expressions, but significantly more readable (IMO).
+
+As an example, here is what `test28.tig` looks like after parsing and
+pretty-printing:
+
+    LetExp[
+        [
+        TypeDecs[
+            TypeDec[
+                arrtype1,
+                ArrayTy[
+                int]],
+            TypeDec[
+                arrtype2,
+                ArrayTy[
+                int]]],
+        VarDec[
+            arr1,
+            arrtype1,
+            ArrayExp[
+                arrtype2,
+                IntExp[
+                    10],
+                IntExp[
+                    0]]]],
+        SeqExp[
+            VarExp[
+                SimpleVar[
+                    arr1]]]]
+
+### Machine
+Will most-likely compile to RISC and execute using SPIM (as favored by Appel)