psxinterpreter: Merge DIV interpreter fix from libretro's fork (#193)

Fix comes from here :
https://github.com/libretro/pcsx_rearmed/pull/530

Co-authored-by: Ember Cold <embercold@outlook.com>

diff --git a/libpcsxcore/psxinterpreter.c b/libpcsxcore/psxinterpreter.c
index fa454e1..e59f93d 100644 (file)
--- a/libpcsxcore/psxinterpreter.c
+++ b/libpcsxcore/psxinterpreter.c
@@ -501,14 +501,27 @@ void psxSLTU()    { if (!_Rd_) return; _rRd_ = _u32(_rRs_) < _u32(_rRt_); }       // Rd
 * Format:  OP rs, rt                                     *
 *********************************************************/
 void psxDIV() {
-       if (_i32(_rRt_) != 0) {
-               _i32(_rLo_) = _i32(_rRs_) / _i32(_rRt_);
-               _i32(_rHi_) = _i32(_rRs_) % _i32(_rRt_);
-       }
-       else {
-               _i32(_rLo_) = _i32(_rRs_) >= 0 ? 0xffffffff : 1;
-               _i32(_rHi_) = _i32(_rRs_);
-       }
+    if (!_i32(_rRt_)) {
+        _i32(_rHi_) = _i32(_rRs_);
+        if (_i32(_rRs_) & 0x80000000) {
+            _i32(_rLo_) = 1;
+        } else {
+            _i32(_rLo_) = 0xFFFFFFFF;
+        }
+/*
+ * Notaz said that this was "not needed" for ARM platforms and could slow it down so let's disable for ARM. 
+ * This fixes a crash issue that can happen when running Amidog's CPU test.
+ * (It still stays stuck to a black screen but at least it doesn't crash anymore)
+ */
+#if !defined(__arm__) && !defined(__aarch64__)
+    } else if (_i32(_rRs_) == 0x80000000 && _i32(_rRt_) == 0xFFFFFFFF) {
+        _i32(_rLo_) = 0x80000000;
+        _i32(_rHi_) = 0;
+#endif
+    } else {
+        _i32(_rLo_) = _i32(_rRs_) / _i32(_rRt_);
+        _i32(_rHi_) = _i32(_rRs_) % _i32(_rRt_);
+    }
 }
 
 void psxDIVU() {