From 22ade3750e242898684f7197406692cc047ad605 Mon Sep 17 00:00:00 2001
From: John Breaux <j@soft.fish>
Date: Tue, 30 Jan 2024 05:29:25 -0600
Subject: [PATCH] grammar.ebnf: Commit incomplete grammar description

---
 grammar.ebnf | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 grammar.ebnf

diff --git a/grammar.ebnf b/grammar.ebnf
new file mode 100644
index 0000000..06704d9
--- /dev/null
+++ b/grammar.ebnf
@@ -0,0 +1,47 @@
+(* Partical grammar for msp430-asm *)
+
+Line = Label | Directive | Insn ;
+
+Insn = NoEm | OneEm | Special | OneArg | TwoArg | Jump ;
+
+(* Instruction formats *)
+NoEm    = OpNoEm ;
+OneEm   = OpOneEm Dst ;
+Special = "reti" | "br" Src ;
+OneArg  = OpOneArg Src ;
+TwoArg  = OpTwoArg Src ','? Dst ;
+Jump    = OpJump Expr ;
+
+
+(* Addressing modes *)
+Src = '#' (SrcSpecial | '-'? Expr)
+    | Absolute
+    | PostInc
+    | Indexed
+    | Direct ;
+
+Dst = '#' (SrcSpecial | Expr)
+    | Absolute
+    | Indirect
+    | Indexed
+    | Direct ;
+
+Direct     = Reg ;
+Indirect   = '@' Reg ;
+PostInc    = Indirect '+'? ;
+Indexed    = Number '(' Reg ')' ;
+Immediate  = '#' Expr ;
+Absolute   = '&' Expr ;
+SrcSpecial = 0 | 1 | '-' 1 | 0xffff | 2 | 4 | 8 ;
+DstSpecial = 0 | 1 ;
+
+Expr       = '-'? Number ;
+
+(* Pseudo-terminals *)
+Reg = "pc"  | "sp"  | "sr"  | "cg" 
+    | "r0"  | "r1"  | "r2"  | "r3" 
+    | "r4"  | "r5"  | "r6"  | "r7" 
+    | "r8"  | "r9"  | "r10" | "r11"
+    | "r12" | "r13" | "r14" | "r15" ;
+Identifier = ID_START ID_CONTINUE* ;
+Number = '-'? DIGIT ;