Added tests, some refactoring, fixed a parsing bug.

filetests/parser/instruction_encoding.cton

@@ -0,0 +1,25 @@
+test cat
+
+isa riscv
+
+; regex: WS=[ \t]*
+
+function foo(i32, i32) {
+ebb1(v0: i32, v1: i32):
+    [-,-] v2 = iadd v0, v1
+    [-] trap
+    [R#1234, %x5, %x11] v6, v7 = iadd_cout v2, v0
+    [Rshamt#beef, %x25] v8 = ishl_imm v6, 2
+    v9 = iadd v8, v7
+    [Iret#5] return v0, v8
+}
+; sameln: function foo(i32, i32) {
+; nextln: $ebb1($v0: i32, $v1: i32):
+; nextln:     [-]$WS $v2 = iadd $v0, $v1
+; nextln:     [-]$WS trap
+; nextln:     [0#1234]$WS $v6, $v7 = iadd_cout $v2, $v0
+; TODO Add the full encoding information available: instruction recipe name and architectural registers if specified
+; nextln:     [2#beef]$WS $v8 = ishl_imm $v6, 2
+; nextln:     [-]$WS $v9 = iadd $v8, $v7
+; nextln:     [3#05]$WS return $v0, $v8
+; nextln: }