From b51d025f1c7342bad03777a1bb74ae7d8eb9e827 Mon Sep 17 00:00:00 2001
From: Kurausukun <lord.uber1@gmail.com>
Date: Sun, 8 Aug 2021 20:33:21 -0400
Subject: [PATCH] port cgb fakematching fixes (thanks to revo)

---
 src/m4a.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/m4a.c b/src/m4a.c
index 105312a40c..ef4c2a537a 100644
--- a/src/m4a.c
+++ b/src/m4a.c
@@ -906,7 +906,6 @@ void CgbSound(void)
 {
     s32 ch;
     struct CgbChannel *channels;
-    s32 envelopeStepTimeAndDir;
     s32 prevC15;
     struct SoundInfo *soundInfo = SOUND_INFO_PTR;
     vu8 *nrx0ptr;
@@ -914,6 +913,7 @@ void CgbSound(void)
     vu8 *nrx2ptr;
     vu8 *nrx3ptr;
     vu8 *nrx4ptr;
+    s32 envelopeStepTimeAndDir;
 
     // Most comparision operations that cast to s8 perform 'and' by 0xFF.
     int mask = 0xff;
@@ -1198,8 +1198,8 @@ void CgbSound(void)
             }
             else
             {
-                envelopeStepTimeAndDir &= 0xf;
-                *nrx2ptr = (channels->envelopeVolume << 4) + envelopeStepTimeAndDir;
+                unsigned int newMask = 0xF;
+                *nrx2ptr = (envelopeStepTimeAndDir & newMask) + (channels->envelopeVolume << 4);
                 *nrx4ptr = channels->n4 | 0x80;
                 if (ch == 1 && !(*nrx0ptr & 0x08))
                     *nrx4ptr = channels->n4 | 0x80;