From 6ee196e6800099d52776bb16f84f26525586958f Mon Sep 17 00:00:00 2001
From: Bobby Bingham <koorogi@koorogi.info>
Date: Wed, 18 Jan 2017 19:10:20 -0600
Subject: nqasm: lex registers as if they were labels

This makes parsing registers trickier, but allows a label to have a name
'r0'-'r7', which would otherwise conflict with the registers.
---
 lexer.l  |  6 ++----
 parser.y | 36 +++++++++++++++++++++++++++---------
 2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/lexer.l b/lexer.l
index 7d44adf..5c8ebfb 100644
--- a/lexer.l
+++ b/lexer.l
@@ -35,7 +35,7 @@ HEX        [0-9a-f]
 %%
 
 <INITIAL>{SP}+           { BEGIN(inst);    return T_SPACE; }
-<INITIAL>{LABEL}         { SETSTR(yytext); return T_LABEL; }
+<INITIAL,args>{LABEL}    { SETSTR(yytext); return T_LABEL; }
 <INITIAL>:{SP}*          { BEGIN(inst);    return T_COLON; }
 
 <inst>add/{EOI}          { BEGIN(args);    return T_ADD;    }
@@ -74,12 +74,10 @@ HEX        [0-9a-f]
 <inst>addpc/{EOI}        { BEGIN(args);    return T_ADDPC;  }
 <inst>nop/{EOI}          { BEGIN(args);    return T_NOP;    }
 
-<args>r{REGNUM}          { SETVALUE(yytext[1]-'0'); return T_REG;    }
-<args>@r{REGNUM}         { SETVALUE(yytext[2]-'0'); return T_REGPTR; }
+<args>@                  { return T_DEREF; }
 <args>[-+]?{DEC}+        { return intlit(yytext,   10, &yylval.lval); }
 <args>0x{HEX}+           { return intlit(yytext+2, 16, &yylval.lval); }
 <args>{SP}*,{SP}*        { return T_COMMA; }
-<args>{LABEL}            { SETSTR(yytext); return T_LABEL; }
 
 {SP}*{COMMENT}?\n        { BEGIN(INITIAL); return T_EOL;    }
 {SP}*{COMMENT}           { BEGIN(INITIAL); return T_EOL;    }
diff --git a/parser.y b/parser.y
index e6cb0b1..f63a70f 100644
--- a/parser.y
+++ b/parser.y
@@ -78,13 +78,13 @@ void yyerror(const char *msg)
 %token <lval> T_INT
 %token        T_BADINT
 
-%token <arg> T_REG
-%token <arg> T_REGPTR
-
 %token       T_COMMA    ","
 %token       T_COLON    ":"
+%token       T_DEREF    "@"
 
 %type <inst> inst
+%type <arg>  reg
+%type <arg>  regp
 %type <arg>  expr
 %type <args> a_reg2
 %type <args> a_reg3
@@ -150,20 +150,38 @@ inst:
 	;
 
 a_reg2:
-	T_SPACE T_REG "," T_REG              { $$ = MKARGS($2, $4);     }
+	T_SPACE reg "," reg                  { $$ = MKARGS($2, $4);     }
 a_reg3:
-	T_SPACE T_REG "," T_REG "," T_REG    { $$ = MKARGS($2, $4, $6); }
+	T_SPACE reg "," reg "," reg          { $$ = MKARGS($2, $4, $6); }
 a_regp:
-	T_SPACE T_REGPTR                     { $$ = MKARGS($2);         }
+	T_SPACE regp                         { $$ = MKARGS($2);         }
 a_regp_reg:
-	T_SPACE T_REGPTR "," T_REG           { $$ = MKARGS($2, $4);     }
+	T_SPACE regp "," reg                 { $$ = MKARGS($2, $4);     }
 a_reg_regp:
-	T_SPACE T_REG "," T_REGPTR           { $$ = MKARGS($2, $4);     }
+	T_SPACE reg "," regp                 { $$ = MKARGS($2, $4);     }
 a_reg_expr:
-	T_SPACE T_REG "," expr               { $$ = MKARGS($2, $4);     }
+	T_SPACE reg "," expr                 { $$ = MKARGS($2, $4);     }
 a_expr:
 	T_SPACE expr                         { $$ = MKARGS($2);         }
 
+regp:	"@" reg { $$ = $2; }
+reg:	T_LABEL {
+			int bad = 0;
+			if ($1[0] != 'r' && $1[0] != 'R')
+				bad = 1;
+			else if (0 > $1[1] - '0' || $1[1] - '0' > 9)
+				bad = 1;
+			else if ($1[2])
+				bad = 1;
+
+			if (bad) {
+				yyerror("invalid register");
+				YYERROR;
+			} else {
+				$$ = MKARGVALUE($1[1] - '0');
+			}
+		}
+
 expr:
 		intlit         { $$ = MKARGVALUE($1); }
 	|	T_LABEL        { $$ = MKARGLABEL($1); }
-- 
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