1 files changed, 128 insertions, 0 deletions
diff --git a/tests/runrom/branching.s b/tests/runrom/branching.s
new file mode 100644
index 0000000..a96888c
--- /dev/null
+++ b/tests/runrom/branching.s
@@ -0,0 +1,128 @@
+.segment "HEADER"
+    .byte 'N', 'E', 'S', $1A
+    .byte $02, $01
+    .byte $00
+    .byte $00
+
+.segment "CHARS"
+.byte 0
+
+.segment "VECTORS"
+    .addr reset, reset, reset
+
+.segment "CODE"
+;; asan:stack full
+
+;; From: https://git.mssola.com/nes/jetpac.nes/.
+.scope Globals
+    ;; | Bit | Short name       | Meaning                  |
+    ;; |-----+------------------+--------------------------|
+    ;; |   7 | enabled          | Multiplayer enabled.     |
+    ;; | 6-3 | -                | Unused.                  |
+    ;; |   2 | player's 2 state | 0: over; 1: alive        |
+    ;; |   1 | player's 1 state | 0: over; 1: alive        |
+    ;; |   0 | active           | 0: player 1; 1: player 2 |
+    zp_multiplayer = $27
+
+    ;; Extra bitmap that was needed beyond the ones that we already have. Yeah,
+    ;; I know, bad planning from my side, but now it's a bit complex to untangle
+    ;; variables like 'Globals::zp_flags'.
+    ;;
+    ;; | Bit | Short name       | Meaning                          |
+    ;; |-----+------------------+----------------------------------|
+    ;; |   7 | score            | The score has been updated.      |
+    ;; |   6 | high             | The high score has been updated. |
+    ;; | 5-0 | -                | Unused.                          |
+    zp_extra_flags = $28
+.endscope
+
+;; From: https://git.mssola.com/nes/jetpac.nes/.
+.scope Score
+    ;; Scores for both players are stored in a single buffer. Even indeces
+    ;; contain digits for the first player, and odd indeces contain digits for
+    ;; the second player. Digits are stored in little-endian format.
+    ;;
+    ;; Interweaving digits this way might seem weird, but it actually makes
+    ;; indexing things super easy: the 'active' bit from
+    ;; 'Globals::zp_multiplayer' can be used to index the first item, and then
+    ;; it's a matter of advancing the 'x' register twice in order to get the
+    ;; next digit.
+    PLAYERS_BUFF_SIZE = $0C
+    m_players = $300     ; asan:reserve PLAYERS_BUFF_SIZE
+
+    ;; The high score for this session.
+    m_hi = $30C           ; asan:reserve $06
+.endscope
+
+;; This is basically Score::save_hi_score() from
+;; https://git.mssola.com/nes/jetpac.nes/.
+.proc reset
+    ;;;
+    ;; Check player 1.
+
+    ldx #(Score::PLAYERS_BUFF_SIZE - 2)
+    ldy #5
+
+@player1_loop:
+    lda Score::m_hi, y
+    cmp Score::m_players, x
+    bcc @save_player1
+    dex
+    dex
+    dey
+    cpy #$FF
+    bne @player1_loop
+
+    ;; No dice! If we are in multiplayer mode, then check player 2,
+    ;; otherwise just quit.
+    bit Globals::zp_multiplayer
+    bpl @end
+
+    ;;;
+    ;; Check player 2.
+
+    ldx #(Score::PLAYERS_BUFF_SIZE - 1)
+    ldy #5
+
+@player2_loop:
+    lda Score::m_hi, y
+    cmp Score::m_players, x
+    bcc @save_player2
+    dex
+    dex
+    dey
+    cpy #$FF
+    bne @player2_loop
+
+    ;; Not player 2 either. Just quit.
+    rts
+
+    ;;;
+    ;; One of the players actually achieved a high score. Let's save it.
+
+@save_player1:
+    ldx #0
+    beq @save
+@save_player2:
+    ldx #1
+
+@save:
+    ldy #0
+@save_loop:
+    lda Score::m_players, x
+    sta Score::m_hi, y
+
+    inx
+    inx
+    iny
+    cpy #6
+    bne @save_loop
+
+    ;; And set the 'high' bit so this change is reflected on screen.
+    lda Globals::zp_extra_flags
+    ora #$40
+    sta Globals::zp_extra_flags
+
+@end:
+    rts
+.endproc