From 66854d4a5b1b980652fe19692896e9ce8a17318c Mon Sep 17 00:00:00 2001
From: glenda <glenda@9front.local>
Date: Wed, 14 Sep 2022 19:47:38 +0000
Subject: [PATCH] Actually assembling to runnable bytecode!

---
 asm.c           | 98 +++++++++++++++++++++++++++++++++++++++++++++----
 tests/hello.asm | 11 ++++++
 2 files changed, 101 insertions(+), 8 deletions(-)
 create mode 100644 tests/hello.asm

diff --git a/asm.c b/asm.c
index 5661cc8..6e0191c 100644
--- a/asm.c
+++ b/asm.c
@@ -2,6 +2,7 @@
 #include <libc.h>
 #include <stdio.h>
 #include "lc3.h"
+#include "util.c"
 #define MAXLINE 256
 #define MAXTOKEN 32
 #define MAXSYMBOL 128
@@ -27,7 +28,7 @@ Symbol symtab[MAXSYMBOL];
 
 // FIXME: Make these dynamic;
 Inst *mem[MEMORY];
-Inst *unmapped[MEMORY];
+u16int unmapped[MEMORY];
 
 int debug = 0;
 int unmappedcount = 0;
@@ -36,6 +37,7 @@ int memc = 0;
 int lineno = 1;
 u16int orig, pc = 0x3000;
 char *asmfile;
+char *outfile;
 
 
 void
@@ -225,7 +227,7 @@ validate(Inst *in)
 			if(in->arg[1][0] == 'x'){
 				in->p_arg[1] = hexnparse(9, in->arg[1]);
 			} else {
-				unmapped[unmappedcount++] = in;
+				unmapped[unmappedcount++] = pc;
 			}
 			break;
 		}
@@ -237,7 +239,7 @@ validate(Inst *in)
 			if(in->arg[0][0] == 'x'){
 				in->p_arg[0] = hexnparse(9, in->arg[0]);
 			} else {
-				unmapped[unmappedcount++] = in;
+				unmapped[unmappedcount++] = pc;
 			}
 			break;
 		case OP_JSR:
@@ -246,7 +248,7 @@ validate(Inst *in)
 				if(in->arg[0][0] == 'x'){
 					in->p_arg[0] = hexnparse(11, in->arg[0]);
 				} else {
-					unmapped[unmappedcount++] = in;
+					unmapped[unmappedcount++] = pc;
 				}
 			} else { // JSRR
 				goto Reg;
@@ -385,18 +387,89 @@ void
 maplabels(void)
 {
 	for(int i = 0; i<unmappedcount; i++){
-		int last = unmapped[i]->argc - 1;
+		int p = unmapped[i] - orig;
+		int last = mem[p]->argc - 1;
+		int offset = 0;
 		int found = 0;
 		for(int j = 0; j<symcount; j++){
-			if(!strcmp(symtab[j].label, unmapped[i]->arg[last])){
-				unmapped[i]->p_arg[last] = symtab[j].addr;
+			if(!strcmp(symtab[j].label, mem[p]->arg[last])){
+				// JSR has 11 bits available for PCoffset, the rest have 9
+				u16int bits = (mem[p]->op == OP_JSR) ? 11 : 9;
+				u16int mask = (mem[p]->op == OP_JSR) ? 0x07FF : 0x01FF;
+				u16int packed_offset;
+				offset = symtab[j].addr - (p + orig + 1);
+				if(offset < 0){
+					packed_offset = offset * -1;
+					packed_offset = ~packed_offset;
+					packed_offset++;
+				}
+				mem[p]->p_arg[last] = packed_offset & mask;
+				/* FIXME: test this
+				if(offset != signextend(mem[p]->p_arg[last], bits))
+					syntaxerr(smprint("Memory offset %x for label %s is too big to fit the argument for opcode %s", offset, symtab[j].label, opcode[mem[p]->op]));
+				*/
 				found++;
 				break;
 			}
 		}
 		if(!found)
-			syntaxerr(smprint("Label %s does not exist!", unmapped[i]->arg[last]));
+			syntaxerr(smprint("Label %s does not exist!", mem[p]->arg[last]));
+	}
+}
+
+long
+writeinst(Inst *i, FILE *f)
+{
+	u16int code = 0;
+	code |= i->op << 12;
+	switch(i->op){
+	case OP_ADD:
+	case OP_AND:
+		code |= i->p_arg[0] << 9;
+		code |= i->p_arg[1] << 6;
+		code |= i->mode << 5;
+		code |= i->p_arg[2];
+		break;
+	case OP_BR:
+		code |= i->mode << 9;
+		code |= i->p_arg[0];
+		break;
+	case OP_JMP:
+		code |= i->p_arg[0] << 6;
+		break;
+	case OP_JSR:
+		code |= i->mode << 11;
+		if(i->mode)
+			code |= i->p_arg[0];
+		else
+			code |= i->p_arg[0] << 6;
+		break;
+	case OP_LD:
+	case OP_LDI:
+	case OP_LEA:
+	case OP_ST:
+	case OP_STI:
+		code |= i->p_arg[0] << 9;
+		code |= i->p_arg[1];
+		break;
+	case OP_LDR:
+	case OP_STR:
+		code |= i->p_arg[0] << 9;
+		code |= i->p_arg[1] << 6;
+		code |= i->p_arg[2];
+		break;
+	case OP_NOT:
+		code |= i->p_arg[0] << 9;
+		code |= i->p_arg[1] << 6;
+		code |= 0x1f;
+		break;
+	case OP_TRAP:
+		code |= i->p_arg[0];
+	case OP_RTI:
+		break;
 	}
+	code = swap16(code);
+	return fwrite(&code, 2, 1, f);
 }
 
 void
@@ -410,9 +483,14 @@ main(int argc, char* argv[])
 		break;
 	case 'f':
 		asmfile = EARGF(usage());
+		break;
+	case 'o':
+		outfile = EARGF(usage());
+		break;
 	} ARGEND;
 
 	in = fopen(asmfile, "r");
+	out = fopen(outfile, "w+");
 	parse(in);
 	if(debug){
 		print("Symbol table:\n");
@@ -435,5 +513,9 @@ main(int argc, char* argv[])
 			print("\n");
 		}
 	}
+	u16int o = swap16(orig);
+	fwrite(&o, 2, 1, out);
+	for(int i = 0; i < memc; i++)
+		writeinst(mem[i], out);
 	exits(nil);
 }
diff --git a/tests/hello.asm b/tests/hello.asm
new file mode 100644
index 0000000..c0aedfd
--- /dev/null
+++ b/tests/hello.asm
@@ -0,0 +1,11 @@
+	.ORIG	x3000
+	ADD	R2,R2,x6	; we need 6 loops to get to 'h'
+	NOT	R2,R2		; we want to be able to subtract this number so we'll 2's complements it
+	ADD	R2,R2,x1
+LOOPH	ADD	R0,R0,xf
+	ADD	R1,R1,x1
+	ADD	R3,R1,R2	; compare if we're at 6 loops yet
+	BRn	LOOPH
+	ADD	R0,R0,xe
+	TRAP	x21
+	.END
-- 
2.45.2