From 31504f85a7998db647d03241289300c8206c9081 Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Thu, 24 May 2018 14:31:21 -0400
Subject: [PATCH 1/2] Interpreter_FloatingPoint: Don't update FPRF in frsqrte
 in certain exceptional cases

If the FPSCR.VE bit is set and an invalid operand is passed in, then the FPRF
shouldn't be updated. Similarly this is also the case when the FPSCR.ZE bit
is set and negative or positive zero is passed in as the operand.
---
 .../Interpreter/Interpreter_FloatingPoint.cpp    | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
index 98a5b8a2c0..f6d63087d7 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
@@ -410,19 +410,29 @@ void Interpreter::fresx(UGeckoInstruction inst)
 
 void Interpreter::frsqrtex(UGeckoInstruction inst)
 {
-  double b = rPS0(inst.FB);
+  const double b = rPS0(inst.FB);
+  const double result = Common::ApproximateReciprocalSquareRoot(b);
 
   if (b < 0.0)
   {
     SetFPException(FPSCR_VXSQRT);
+
+    if (FPSCR.VE == 0)
+      PowerPC::UpdateFPRF(result);
   }
   else if (b == 0.0)
   {
     SetFPException(FPSCR_ZX);
+
+    if (FPSCR.ZE == 0)
+      PowerPC::UpdateFPRF(result);
+  }
+  else
+  {
+    PowerPC::UpdateFPRF(result);
   }
 
-  rPS0(inst.FD) = Common::ApproximateReciprocalSquareRoot(b);
-  PowerPC::UpdateFPRF(rPS0(inst.FD));
+  rPS0(inst.FD) = result;
 
   if (inst.Rc)
     Helper_UpdateCR1();

From 155bcb1649e35ec277babe5c864f2fe8f706ba2c Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Thu, 24 May 2018 14:37:05 -0400
Subject: [PATCH 2/2] Interpreter_FloatingPoint: Set FPSCR.VXSNAN if the input
 to frsqrte is a signaling NaN

If the input is a signaling NaN, then we need to signal that via setting
the FPSCR.VXSNAN bit. We also shouldn't update the FPRF flags if
FPSCR.VE is set.
---
 .../Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
index f6d63087d7..e88d97b3cf 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FloatingPoint.cpp
@@ -427,6 +427,13 @@ void Interpreter::frsqrtex(UGeckoInstruction inst)
     if (FPSCR.ZE == 0)
       PowerPC::UpdateFPRF(result);
   }
+  else if (Common::IsSNAN(b))
+  {
+    SetFPException(FPSCR_VXSNAN);
+
+    if (FPSCR.VE == 0)
+      PowerPC::UpdateFPRF(result);
+  }
   else
   {
     PowerPC::UpdateFPRF(result);