From 8a79f9099cebad4e4517ed7d89418ac23faef32f Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Wed, 23 May 2018 19:45:24 -0400
Subject: [PATCH 1/2] Interpreter_FloatingPoint: Set FPSCR.VXSNAN if input to
 fres is a signaling NaN

fres is defined as having the VXSNAN bit set if an input to the
instruction is a signaling NaN
---
 .../Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
index 98a5b8a2c0..18a33a1a5e 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
@@ -394,7 +394,7 @@ void Interpreter::fdivsx(UGeckoInstruction inst)
 // Single precision only.
 void Interpreter::fresx(UGeckoInstruction inst)
 {
-  double b = rPS0(inst.FB);
+  const double b = rPS0(inst.FB);
   rPS0(inst.FD) = rPS1(inst.FD) = Common::ApproximateReciprocal(b);
 
   if (b == 0.0)
@@ -402,6 +402,11 @@ void Interpreter::fresx(UGeckoInstruction inst)
     SetFPException(FPSCR_ZX);
   }
 
+  if (Common::IsSNAN(b))
+  {
+    SetFPException(FPSCR_VXSNAN);
+  }
+
   PowerPC::UpdateFPRF(rPS0(inst.FD));
 
   if (inst.Rc)

From 34adc529a77d6efb64774ea23b69ac8835609b47 Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Wed, 23 May 2018 23:31:56 -0400
Subject: [PATCH 2/2] Interpreter_FloatingPoint: Don't update the FPRF in fres
 in certain exceptional cases

If FPSCR.ZE is set and a divide by zero exception is signaled, then the
FPRF shouldn't be updated with a result. Similarly, if the input is an
SNaN and FPSCR.VE is set, then the FPRF shouldn't be updated.
---
 .../Interpreter/Interpreter_FloatingPoint.cpp | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
index 18a33a1a5e..cab27b3dd7 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
@@ -395,19 +395,28 @@ void Interpreter::fdivsx(UGeckoInstruction inst)
 void Interpreter::fresx(UGeckoInstruction inst)
 {
   const double b = rPS0(inst.FB);
-  rPS0(inst.FD) = rPS1(inst.FD) = Common::ApproximateReciprocal(b);
+  const double result = Common::ApproximateReciprocal(b);
+
+  rPS0(inst.FD) = rPS1(inst.FD) = result;
 
   if (b == 0.0)
   {
     SetFPException(FPSCR_ZX);
-  }
 
-  if (Common::IsSNAN(b))
+    if (FPSCR.ZE == 0)
+      PowerPC::UpdateFPRF(result);
+  }
+  else if (Common::IsSNAN(b))
   {
     SetFPException(FPSCR_VXSNAN);
-  }
 
-  PowerPC::UpdateFPRF(rPS0(inst.FD));
+    if (FPSCR.VE == 0)
+      PowerPC::UpdateFPRF(result);
+  }
+  else
+  {
+    PowerPC::UpdateFPRF(result);
+  }
 
   if (inst.Rc)
     Helper_UpdateCR1();