From: gameblabla <gameblabla@users.noreply.github.com>
Date: Sun, 22 Aug 2021 22:31:18 +0000 (+0000)
Subject: psxinterpreter: Merge DIV interpreter fix from libretro's fork (#193)
X-Git-Tag: r23~132
X-Git-Url: https://notaz.gp2x.de/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a4ae39973ff2e77b233c467fbd0e49cc55d72f56;p=pcsx_rearmed.git

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 fa454e1a..e59f93d8 100644
--- 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() {