From 1e0d0202e614f398f491624c84ae9a8309fa2f96 Mon Sep 17 00:00:00 2001
From: Bobby Bingham <koorogi@koorogi.info>
Date: Wed, 18 Jan 2017 19:20:20 -0600
Subject: nqasm: allow "." to refer to current pc in immediate operand

---
 lexer.l  | 1 +
 nqasm.c  | 8 ++++----
 nqasm.h  | 1 +
 parser.y | 3 +++
 4 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/lexer.l b/lexer.l
index 5c8ebfb..053ac4e 100644
--- a/lexer.l
+++ b/lexer.l
@@ -74,6 +74,7 @@ HEX        [0-9a-f]
 <inst>addpc/{EOI}        { BEGIN(args);    return T_ADDPC;  }
 <inst>nop/{EOI}          { BEGIN(args);    return T_NOP;    }
 
+<args>\.                 { return T_DOT; }
 <args>@                  { return T_DEREF; }
 <args>[-+]?{DEC}+        { return intlit(yytext,   10, &yylval.lval); }
 <args>0x{HEX}+           { return intlit(yytext+2, 16, &yylval.lval); }
diff --git a/nqasm.c b/nqasm.c
index 0b0bbd8..ee3010a 100644
--- a/nqasm.c
+++ b/nqasm.c
@@ -56,12 +56,12 @@ void add_instruction(const struct instruction *inst)
 	addr += 2;
 }
 
-static long eval_argument(const struct argument *arg)
+static long eval_argument(const struct argument *arg, uint16_t pc)
 {
 	struct label *l;
 	switch (arg->type) {
-	case ARG_INTEGER:
-		return arg->value;
+	case ARG_INTEGER: return arg->value;
+	case ARG_PC:      return pc;
 
 	case ARG_LABEL:
 		l = vector_search(&labels->v, &(struct label) { .name = arg->label }, cmp_label);
@@ -82,7 +82,7 @@ static void assemble_instruction(const struct instruction *inst, uint16_t pc)
 	const struct operand  *ops  = mnem->operands;
 	const struct argument *args = inst->args.args;
 	for (int i = 0; i < 3 && ops[i].type; i++) {
-		long value = eval_argument(args + i);
+		long value = eval_argument(args + i, pc);
 
 		switch (ops[i].type) {
 		case REG:
diff --git a/nqasm.h b/nqasm.h
index f2e036d..0bc51f7 100644
--- a/nqasm.h
+++ b/nqasm.h
@@ -3,6 +3,7 @@
 
 #define ARG_INTEGER   0
 #define ARG_LABEL     1
+#define ARG_PC        2
 
 struct argument {
 	int type;
diff --git a/parser.y b/parser.y
index e698e47..2ec2264 100644
--- a/parser.y
+++ b/parser.y
@@ -15,6 +15,7 @@ void yyerror(const char *msg)
 #define MKARGS(...)           (struct arguments)   { { __VA_ARGS__ } }
 #define MKARGVALUE(v)         (struct argument)    { .type = ARG_INTEGER, .value = (v) }
 #define MKARGLABEL(l)         (struct argument)    { .type = ARG_LABEL,   .label = (l) }
+#define MKARGTYPE(t)          (struct argument)    { .type = (t) }
 
 %}
 
@@ -80,6 +81,7 @@ void yyerror(const char *msg)
 
 %token       T_COMMA    ","
 %token       T_COLON    ":"
+%token       T_DOT      "."
 %token       T_DEREF    "@"
 
 %type <inst> inst
@@ -178,6 +180,7 @@ reg:	T_LABEL {
 expr:
 		intlit         { $$ = MKARGVALUE($1); }
 	|	T_LABEL        { $$ = MKARGLABEL($1); }
+	|	"."            { $$ = MKARGTYPE(ARG_PC); }
 	;
 
 intlit:	T_INT
-- 
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