From 965b963a6f62bec45c0810c01ab5a8a1aa231463 Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Thu, 12 Apr 2018 01:40:55 -0400
Subject: [PATCH 1/2] Interpreter_FloatingPoint: Handle SNaNs properly in frsp

If FPSCR[VE] is set, a result isn't supposed to be written to the destination,
just the FPSCR[VXSNAN] bit gets set, and FPSCR[FR] and FPSCR[FI] get set to zero.

If FPSCR[VE] isn't set, then we do write out a result, however, the FPSCR[FPRF]
field is updated to signify a QNaN (yes, a QNaN, the FPRF field doesn't have
a bit configuration for SNaNs).
---
 .../Interpreter/Interpreter_FloatingPoint.cpp | 31 +++++++++++++++----
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
index 4529d2ebe8..69f3a93de8 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
@@ -272,12 +272,31 @@ void Interpreter::fselx(UGeckoInstruction inst)
 // PS1 is said to be undefined
 void Interpreter::frspx(UGeckoInstruction inst)  // round to single
 {
-  double b = rPS0(inst.FB);
-  double rounded = ForceSingle(b);
-  SetFI(b != rounded);
-  FPSCR.FR = fabs(rounded) > fabs(b);
-  PowerPC::UpdateFPRF(rounded);
-  rPS0(inst.FD) = rPS1(inst.FD) = rounded;
+  const double b = rPS0(inst.FB);
+  const double rounded = ForceSingle(b);
+
+  if (MathUtil::IsSNAN(b))
+  {
+    SetFPException(FPSCR_VXSNAN);
+
+    if (FPSCR.VE == 0)
+    {
+      rPS0(inst.FD) = rounded;
+      rPS1(inst.FD) = rounded;
+      PowerPC::UpdateFPRF(b);
+    }
+
+    SetFI(0);
+    FPSCR.FR = 0;
+  }
+  else
+  {
+    SetFI(b != rounded);
+    FPSCR.FR = fabs(rounded) > fabs(b);
+    PowerPC::UpdateFPRF(rounded);
+    rPS0(inst.FD) = rounded;
+    rPS1(inst.FD) = rounded;
+  }
 
   if (inst.Rc)
     Helper_UpdateCR1();

From a36bf438cde503f98964af16a958891ad9cd8ff9 Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Thu, 12 Apr 2018 02:51:37 -0400
Subject: [PATCH 2/2] Interpreter_FloatingPoint: Handle QNaNs properly in frsp

Essentially the same behavior as the SNaN path, minus the conditional result and setting of the VXSNAN FPSCR bit.
---
 .../PowerPC/Interpreter/Interpreter_FloatingPoint.cpp    | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
index 69f3a93de8..911f06af3b 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
@@ -275,11 +275,14 @@ void Interpreter::frspx(UGeckoInstruction inst)  // round to single
   const double b = rPS0(inst.FB);
   const double rounded = ForceSingle(b);
 
-  if (MathUtil::IsSNAN(b))
+  if (std::isnan(b))
   {
-    SetFPException(FPSCR_VXSNAN);
+    const bool is_snan = MathUtil::IsSNAN(b);
 
-    if (FPSCR.VE == 0)
+    if (is_snan)
+      SetFPException(FPSCR_VXSNAN);
+
+    if (!is_snan || FPSCR.VE == 0)
     {
       rPS0(inst.FD) = rounded;
       rPS1(inst.FD) = rounded;