From 890448567900ce815a5e4a276e2043ec7679ff5f Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Thu, 20 Dec 2018 17:57:13 +0100
Subject: [PATCH] Implement a small elf-script to C transpiler.

---
 2018/other/elf2c.py | 162 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100755 2018/other/elf2c.py

diff --git a/2018/other/elf2c.py b/2018/other/elf2c.py
new file mode 100755
index 0000000..8d5102b
--- /dev/null
+++ b/2018/other/elf2c.py
@@ -0,0 +1,162 @@
+#!/usr/bin/env python3
+import argparse
+import string
+import textwrap
+import sys
+
+
+def preamble():
+    return textwrap.dedent('''\
+            #include <stdio.h>
+            #include <stdlib.h>
+
+            int main() {
+                int a = 1;
+                int b = 0;
+                int c = 0;
+                int d = 0;
+                int e = 0;
+                int f = 0;''')
+
+
+def footer():
+    return textwrap.dedent('''\
+                program_end:
+                printf("[%d, %d, %d, %d, %d, %d]", a, b, c, d, e, f);
+            }''')
+
+
+def reg_name(num):
+    return string.ascii_lowercase[num]
+
+
+def exhaustive_jump(reg, base, lines):
+    code = '{\n\tswitch (%s + %s) {\n' % (reg_name(reg), base)
+    for i in range(lines):
+        code += '\t\tcase %d: goto line_%d;\n' % (i, i)
+
+    code += textwrap.dedent('''\
+                    default: abort();
+                }
+            }''')
+
+    return code
+
+
+def get_var(ir, var, ip, i):
+    if ir == 'i':
+        return var
+    elif var == ip:
+        return i
+    else:
+        return reg_name(var)
+
+
+def compile(lines):
+    ip = int(next(lines).strip().split()[-1])
+
+    lines = [line for line in lines]
+
+    code = []
+
+    cond = None
+
+    for i, line in enumerate(lines):
+        line = line.strip()
+        parts = line.split()
+        op = parts[0]
+        var = [int(x) for x in parts[1:]]
+
+        code_line = 'line_%d:\n' % i
+        if cond is not None:
+            code_line += '\t'
+        if var[2] == ip:
+            target = None
+            target_reg = None
+            if op == 'seti':
+                target = var[0]
+            elif op == 'addi':
+                if var[0] == ip:
+                    target = i + var[1]
+                else:
+                    sys.exit('Illegal jump at \'%s\'' % line)
+            elif op == 'addr':
+                if var[0] == ip and cond == var[1] \
+                        or var[1] == ip and cond == var[0]:
+                    target = i + 1
+                else:
+                    if var[0] == ip:
+                        target_reg = var[1]
+                    elif var[1] == ip:
+                        target_reg = var[0]
+                    else:
+                        sys.exit('Illegal jump at \'%s\'' % line)
+            elif op == 'mulr':
+                if var[0] == ip and var[1] == ip:
+                    target = i * i
+                else:
+                    sys.exit('Illegal jump at \'%s\'' % line)
+            else:
+                sys.exit('Illegal jump at \'%s\'' % line)
+
+            cond = None
+            if target is not None:
+                if target + 1 < len(lines):
+                    code_line += 'goto line_%d;' % (target + 1)
+                else:
+                    code_line += 'goto program_end;'
+            elif target_reg is not None:
+                code_line += exhaustive_jump(target_reg, i + 1, len(lines))
+            else:
+                sys.exit('Invalid compiler state')
+        else:
+            cond = None
+            if op[:2] in ['gt', 'eq']:
+                cond = var[2]
+                if op[:2] == 'gt':
+                    comp = '>'
+                else:
+                    comp = '=='
+
+                var1 = get_var(op[2], var[0], ip, i)
+                var2 = get_var(op[3], var[1], ip, i)
+                code_line += 'if (%s %s %s)' % (var1, comp, var2)
+            elif op[:3] == 'set':
+                var1 = get_var(op[3], var[0], ip, i)
+                target = reg_name(var[2])
+                code_line += '%s = %s;' % (target, var1)
+            else:
+                var1 = get_var('r', var[0], ip, i)
+                var2 = get_var(op[3], var[1], ip, i)
+                target = reg_name(var[2])
+
+                ops = {
+                        'mul': '*',
+                        'add': '+',
+                        'bor': '|',
+                        'ban': '&',
+                        }
+
+                op = ops[op[:3]]
+                code_line += '%s = %s %s %s;' % (target, var1, op, var2)
+
+        code.append(code_line)
+
+    print(preamble())
+    print('\n'.join(code))
+    print(footer())
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('file')
+
+    args = parser.parse_args()
+    with open(args.file, 'rt') as f:
+        compile(f)
+
+    pass
+
+
+if __name__ == '__main__':
+    main()