Compile something

It's just an integer, but it actually is a number, and it exports and
builds and runs properly...  That's... more than I knew before!

!!!!

scm/inc/.gitignore

@@ -0,0 +1,2 @@
scheme
integers.s

scm/inc/Makefile

@@ -1,2 +1,11 @@
run-scheme: scheme
	./scheme
scheme: scheme.s driver.c
	gcc -O3 scheme.s driver.c -o $@
scheme.s: compiler.scm
	petite --script compiler.scm > $@
integers.s: integers.c
	gcc -O3 --omit-frame-pointer -S $<

scm/inc/compiler.scm

@@ -0,0 +1,17 @@
(define (emit1 instr arg)
  (display "\t")
  (display (format instr arg))
  (display "\n"))
(define (emit0 instr)
  (display "\t")
  (display instr)
  (display "\n"))
(define (compile-program x)
  (display "\t.globl scheme_entry\n\n")
  (display "scheme_entry:\n")
  (emit1 "movl $~a, %eax" x)
  (emit0 "ret"))
(compile-program 42)

scm/inc/driver.c

@@ -0,0 +1,10 @@
/* a simple driver for scheme_entry */
#include <stdio.h>
int scheme_entry();
int main(int argc, char **argv) {
	printf("%d\n", scheme_entry());
	return 0;
}

scm/inc/scheme.s

@@ -0,0 +1,5 @@
	.globl scheme_entry
scheme_entry:
	movl $42, %eax
	ret