GBA BIOS: Fix ArcTan2 accuracy and boundary conditions

mgba-emu · Jun 16, 2016 · 415298e · 415298e
1 parent eb6cedd
commit 415298e
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Showing 2 changed files with 2 additions and 1 deletion.
diff --git a/CHANGES b/CHANGES
@@ -27,6 +27,7 @@ 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
@@ -304,7 +304,7 @@ 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: