GOTO command got performance optimization

src/basic/basic_commands/cmd_run_goto.s

@@ -6,32 +6,83 @@
 cmd_run:
 
 	// RUN clears all variables
+
 	jsr do_clr
 
-cmd_goto:
+	// Initialize OLDTXT pointer, disable Kernal messages
 
-	// XXX optimize this: deduplicate last part (and init_oldtxt) with load/verify,
-	// if line number greater than current line - find line backwards
-
-	// Disable Kernal messages
+	jsr init_oldtxt
 	lda #$00
 	jsr JSETMSG
 
-	// Reset line pointer to first line of program.
-	jsr init_oldtxt
+	// Check if we have any paramenters
 
 	jsr is_end_of_statement
-	bcs !+
+	bcs cmd_run_goto_launch
+
+	// FALLTROUGH
+
+cmd_goto:
+
+	// GOTO requires line number
 
 	jsr fetch_line_number
 	bcs_16 do_SYNTAX_error
-	jsr find_line
-	bcc !+
-	// Line does not exist, so report error
-	jmp do_UNDEFD_STATEMENT_error
+
+	// Check for direct mode
+
+	lda CURLIN+1
+	bmi cmd_goto_direct
+
+	// Not a direct mode - compare desired line number (LINNUM) with the current one (CURLIN)
+
+	lda LINNUM+1
+	cmp CURLIN+1
+	bne !+
+	lda LINNUM+0
+	cmp CURLIN+0
 !:
+	// If desired line number is lower - search line number from start
+
+	bcc cmd_goto_from_start
+
+	// Else - search from the current line
+
+	jsr find_line_from_current
+
+#if HAS_OPCODES_65C02
+	bra cmd_goto_check
+#else
+	jmp cmd_goto_check
+#endif
+
+cmd_goto_direct:
+
+	// Disable Kernal messages
+
+	lda #$00
+	jsr JSETMSG
+
+	// FALLTROUGH
+
+cmd_goto_from_start:
+
+	// Direct mode - find the line from the beginning
+
+	jsr find_line_from_start
+
+	// FALLTROUGH
+
+cmd_goto_check:
+
+	bcs_16 do_UNDEFD_STATEMENT_error
+
+	// FALLTROUGH
+
+cmd_run_goto_launch:
+
 	// Run it!
-	
+
 	pha
 	pha
 	jmp execute_line