[Ongoing] Rewrite frontend to use Flex/Bison

This is a merge of another experiment, so the changes are large:

- separated "modules" directory into frontend/backend
  - adjusted module names and moved files for this to happen
- removed modules lexer & parser
- removed all the unit tests (most were outdated)
- added Bison, flex, and C development tools to manifest.scm
- added lexer.l, a source file used by the flex utility with a functioning lexing implementation
- added parser.y, a source file used by the bison utility with a functioning parser implementation
- added node.c and node.h, which parser.y uses to construct an AST of a C source file (up to binary ops)
- added driver.c, a Guile-C interface that provides a module to scheme programs
- added a Makefile to make all of this
- added stuff to .gitignore

2 files changed, 45 insertions, 0 deletions

diff --git a/src/backend/tacky/driver.scm b/src/backend/tacky/driver.scm
new file mode 100644
index 0000000..b9585c7
--- /dev/null
+++ b/src/backend/tacky/driver.scm
@@ -0,0 +1,6 @@
+(define-module (backend tacky driver)
+  #:export (ast->tacky))
+
+
+(define (ast->tacky n)
+  (eval n (resolve-module '(backend tacky traverse))))
diff --git a/src/backend/tacky/traverse.scm b/src/backend/tacky/traverse.scm
new file mode 100644
index 0000000..9a1b7aa
--- /dev/null
+++ b/src/backend/tacky/traverse.scm
@@ -0,0 +1,39 @@
+(define-module (backend tacky traverse)
+  #:use-module (backend ast ir)
+  #:export (func
+            stmt
+            unary
+            const))
+
+
+(define (func name instrs)
+  (list 'srout name instrs))
+
+(define (stmt val)
+  (list 'instrs
+        (cons 'list (append (cdr val)
+                            (list (list 'ret (car val)))))))
+
+(define (expr op val)
+  (make-instruction op (car val) (cdr val)))
+
+(define (const val)
+  (cons (imm val) '()))
+
+(define (make-instruction op src instrs)
+  (let ((dst (make-temporary)))
+    (cons dst
+          (append instrs
+                  (list (op src dst))))))
+
+(define make-temporary
+  (let ((count 100))
+    (lambda ()
+      (set! count (1+ count))
+      (list 'tmp count))))
+
+(define (neg src dst)
+  (list 'neg src dst))
+
+(define (not src dst)
+  (list 'not src dst))