Add readme for the C compiler

Author: simon816

README.md

@@ -11,6 +11,11 @@ in Minecraft 1.12, Command Block Assembly now outputs functions.
 Functions greatly increase the speed of execution, so Command Block Assembly
 keeps the usage of command blocks to a minimum.
 
+# C Compiler
+
+There is a C compiler that compiles to this assembly language,
+read more [here](https://github.com/simon816/Command-Block-Assembly/blob/master/README_C.md).
+
 # The Assembly Language
 
 It is a simple language with instructions similar to that of x86.
@@ -305,9 +310,6 @@ Instead, they evaluate the most recent CMP instruction.
 The assembler keeps a reference to the most recent CMP instruction. If a conditional jump instruction
 is encountered, it fetches this CMP to decide whether to jump or not.
 
-For almost all use-cases, this should not matter, but it's something to keep in mind and may not be what
-one anticipates.
-
 A more accurate conditional jump could be an instruction that takes 3 arguments e.g: `JL left, right, label`.
 However writing out the comparison is clunky when performing a succinct multi-jump like this:
 ```asm

README_C.md

@@ -0,0 +1,50 @@
+The C Compiler
+==============
+
+The compiler takes a C file and converts it to Command Block Assembly instructions,
+then feeds that to the assembler to generate the final output.
+
+Almost all language features are supported, including a preprocessor with macros.
+
+
+There is only one built-in type, `int`. Fundamentally, all data is stored in a scoreboard objective
+which is a 32 bit signed integer.
+
+The compiler is invoked by calling `compiler_main.py`.
+
+The parameters are similar to the assembler, with the addition of `--page-size` and `--dump-asm`.
+
+
+Command line parameters:
+```
+usage: compiler_main.py [-h] [--world-dir WORLD_DIR] [--namespace NAMESPACE]
+                        [--rem-existing] [--debug] [--stack STACK] [--arg ARG]
+                        [--place-location PLACE_LOCATION] [--enable-sync]
+                        [--page-size PAGE_SIZE] [--dump-asm]
+                        file
+
+positional arguments:
+  file                  C File
+
+optional arguments:
+  -h, --help            show this help message and exit
+  --world-dir WORLD_DIR
+                        World Directory
+  --namespace NAMESPACE
+                        Function namespace
+  --rem-existing        Remove existing functions in namespace
+  --debug               Enable debug output
+  --stack STACK         Stack size
+  --arg ARG             ASM file arguments
+  --place-location PLACE_LOCATION
+                        Location to place command blocks
+  --enable-sync         Enable SYNC opcode
+  --page-size PAGE_SIZE
+                        Memory page size
+  --dump-asm            Dump generated ASM
+```
+
+There are some examples in the [examples](https://github.com/simon816/Command-Block-Assembly/tree/master/examples) directory.
+
+The [mclib.h](https://github.com/simon816/Command-Block-Assembly/blob/master/examples/mclib.h) file
+contains several useful macros and definitions.

compiler/asm_extensions.py

@@ -54,6 +54,12 @@ def __init__(self):
             'MOVINDS': self.handle_mov_ind_s
         })
 
+    def handle_ret(self):
+        if not self.enable_sync:
+            # No need to warn here, the compiler is safe with CALL/RET
+            return
+        super().handle_ret()
+
     def handle_mov_ind(self, src, s_off, dest, d_off):
         """Move indirect src to indirect dest"""
         src, dest = self.get_src_dest(src, dest)

compiler_main.py

@@ -11,15 +11,14 @@
 
 if __name__ == '__main__':
     parser = argparse.ArgumentParser()
-    parser.add_argument('file', help="ASM File", type=argparse.FileType('r'))
+    parser.add_argument('file', help="C File", type=argparse.FileType('r'))
     parser.add_argument('--world-dir', help="World Directory")
     parser.add_argument('--namespace', help="Function namespace", default='c_generated')
     parser.add_argument('--rem-existing', help="Remove existing functions in namespace",
                         action='store_true')
     parser.add_argument('--debug', action='store_true', help="Enable debug output")
     parser.add_argument('--stack', help="Stack size", type=int, default=8)
     parser.add_argument('--arg', help="ASM file arguments", action='append')
-    parser.add_argument('--jump', help='Output subroutine jump instruction')
     parser.add_argument('--place-location', default="~1,~,~1",
                         help="Location to place command blocks")
     parser.add_argument('--enable-sync', help="Enable SYNC opcode", action='store_true')
@@ -69,7 +68,8 @@
     print ('/' + setup)
     print('== Cleanup command ==')
     print('/' + cleanup)
-
-    if args.jump:
-        print('== Jump to %s command ==' % args.jump)
-        print('/' + assembler.get_sub_jump_command(args.jump).resolve(session.scope))
+    if 'main' in assembler.subroutines:
+        print('== Run main() ==')
+        print('/' + assembler.get_sub_jump_command('main').resolve(session.scope))
+    else:
+        print('Cannot output jump: No main() function')

examples/hdd_driver.c

@@ -17,7 +17,7 @@ int __hdd_mul;
 void memory_seek();
 
 void read_mem() {
-    CMD(summon armor_stand $arg:mem_loc$ {Tags:["$tag:_mem_ptr"], NoGravity:1b, Marker: 1b});
+    CMD(summon armor_stand $arg:mem_loc$ {Tags:["$tag:_mem_ptr$"], NoGravity:1b, Marker: 1b});
     __hdd_addr = mar;
     mbr = 0;
     __hdd_addr /= MEM_SIZE_X;
@@ -39,7 +39,7 @@ void read_mem() {
 int __mem_temp;
 
 void write_mem() {
-    CMD(summon armor_stand $arg:mem_loc$ {Tags:["$tag:_mem_ptr"], NoGravity:1b, Marker: 1b});
+    CMD(summon armor_stand $arg:mem_loc$ {Tags:["$tag:_mem_ptr$"], NoGravity:1b, Marker: 1b});
     __hdd_addr = mar;
     __hdd_addr /= MEM_SIZE_X;
     memory_seek();

examples/mem_test.c

@@ -0,0 +1,26 @@
+#include "hdd_driver.c"
+
+int count;
+
+void main() {
+    count = 0;
+    while (count != 64) {
+        mar = count;
+        mbr = count;
+        write_mem();
+        sync;
+        count += 1;
+    }
+}
+
+
+void clear() {
+    count = 0;
+    mbr = 0;
+    while (count != 64) {
+        mar = count;
+        write_mem();
+        sync;
+        count += 1;
+    }
+}