From a5132a7b8f2727a33f0a1a0e4347025fb581bf67 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Thu, 16 Jun 2016 00:19:20 -0700
Subject: [PATCH] GBA BIOS: Fix ArcTan2 accuracy and boundary conditions

---
 CHANGES        | 1 +
 src/gba/bios.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index 91eee9769..77e3446b7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -22,6 +22,7 @@ Bugfixes:
  - ARM7: Fix flags on SBC/RSC
  - Util: Fix realloc semantics in utf16to8
  - ARM7: Fix setting spsr privilege bits when spsr is empty
+ - GBA BIOS: Fix ArcTan2 accuracy and boundary conditions
 Misc:
  - GBA: Slightly optimize GBAProcessEvents
  - Qt: Add preset for DualShock 4
diff --git a/src/gba/bios.c b/src/gba/bios.c
index 5afdd73df..9895155e5 100644
--- a/src/gba/bios.c
+++ b/src/gba/bios.c
@@ -301,7 +301,7 @@ void GBASwi16(struct ARMCore* cpu, int immediate) {
 		cpu->gprs[0] = sqrt((uint32_t) cpu->gprs[0]);
 		break;
 	case 0xA:
-		cpu->gprs[0] = atan2f(cpu->gprs[1] / 16384.f, cpu->gprs[0] / 16384.f) / (2 * M_PI) * 0x10000;
+		cpu->gprs[0] = (uint16_t) (atan2f(cpu->gprs[1] / 16384.f, cpu->gprs[0] / 16384.f) / (2 * M_PI) * 0x10001);
 		break;
 	case 0xB:
 	case 0xC: