diff --git a/Source/Core/Common/MathUtil.h b/Source/Core/Common/MathUtil.h
index 0febed3014..9ddacd6e1c 100644
--- a/Source/Core/Common/MathUtil.h
+++ b/Source/Core/Common/MathUtil.h
@@ -20,16 +20,18 @@ inline void Clamp(T* val, const T& min, const T& max)
 		*val = max;
 }
 
+// The most significant bit of the fraction is an is-quiet bit on all architectures we care about.
 
 static const u64 DOUBLE_SIGN = 0x8000000000000000ULL,
-	DOUBLE_EXP  = 0x7FF0000000000000ULL,
-	DOUBLE_FRAC = 0x000FFFFFFFFFFFFFULL,
-	DOUBLE_ZERO = 0x0000000000000000ULL;
+                 DOUBLE_EXP  = 0x7FF0000000000000ULL,
+                 DOUBLE_FRAC = 0x000FFFFFFFFFFFFFULL,
+                 DOUBLE_ZERO = 0x0000000000000000ULL,
+                 DOUBLE_QBIT = 0x0008000000000000ULL;
 
 static const u32 FLOAT_SIGN = 0x80000000,
-	FLOAT_EXP  = 0x7F800000,
-	FLOAT_FRAC = 0x007FFFFF,
-	FLOAT_ZERO = 0x00000000;
+                 FLOAT_EXP  = 0x7F800000,
+                 FLOAT_FRAC = 0x007FFFFF,
+                 FLOAT_ZERO = 0x00000000;
 
 union IntDouble {
 	double d;
@@ -40,34 +42,41 @@ union IntFloat {
 	u32 i;
 };
 
+inline bool IsINF(double d)
+{
+	IntDouble x; x.d = d;
+	return (x.i & ~DOUBLE_SIGN) == DOUBLE_EXP;
+}
+
 inline bool IsNAN(double d)
 {
 	IntDouble x; x.d = d;
-	return ( ((x.i & DOUBLE_EXP) == DOUBLE_EXP) &&
-			 ((x.i & DOUBLE_FRAC) != DOUBLE_ZERO) );
+	return ((x.i & DOUBLE_EXP) == DOUBLE_EXP) &&
+	       ((x.i & DOUBLE_FRAC) != DOUBLE_ZERO);
 }
 
 inline bool IsQNAN(double d)
 {
 	IntDouble x; x.d = d;
-	return ( ((x.i & DOUBLE_EXP) == DOUBLE_EXP) &&
-		     ((x.i & 0x0007fffffffffffULL) == 0x000000000000000ULL) &&
-		     ((x.i & 0x000800000000000ULL) == 0x000800000000000ULL) );
+	return ((x.i & DOUBLE_EXP) == DOUBLE_EXP) &&
+	       ((x.i & DOUBLE_QBIT) == DOUBLE_QBIT);
 }
 
 inline bool IsSNAN(double d)
 {
 	IntDouble x; x.d = d;
-	return( ((x.i & DOUBLE_EXP) == DOUBLE_EXP) &&
-			((x.i & DOUBLE_FRAC) != DOUBLE_ZERO) &&
-			((x.i & 0x0008000000000000ULL) == DOUBLE_ZERO) );
+	return ((x.i & DOUBLE_EXP) == DOUBLE_EXP) &&
+	       ((x.i & DOUBLE_FRAC) != DOUBLE_ZERO) &&
+	       ((x.i & DOUBLE_QBIT) == DOUBLE_ZERO);
 }
 
 inline float FlushToZero(float f)
 {
 	IntFloat x; x.f = f;
 	if ((x.i & FLOAT_EXP) == 0)
+	{
 		x.i &= FLOAT_SIGN;  // turn into signed zero
+	}
 	return x.f;
 }
 
@@ -75,7 +84,9 @@ inline double FlushToZero(double d)
 {
 	IntDouble x; x.d = d;
 	if ((x.i & DOUBLE_EXP) == 0)
+	{
 		x.i &= DOUBLE_SIGN;  // turn into signed zero
+	}
 	return x.d;
 }
 
diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FPUtils.h b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FPUtils.h
index fa5e6ff2f4..72136d71d3 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_FPUtils.h
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_FPUtils.h
@@ -33,22 +33,19 @@ const u32 FPSCR_VXSQRT     = (u32)1 << (31 - 22);
 const u32 FPSCR_VXCVI      = (u32)1 << (31 - 23);
 
 const u32 FPSCR_VX_ANY     = FPSCR_VXSNAN | FPSCR_VXISI | FPSCR_VXIDI | FPSCR_VXZDZ |
-							 FPSCR_VXIMZ | FPSCR_VXVC | FPSCR_VXSOFT | FPSCR_VXSQRT | FPSCR_VXCVI;
+                             FPSCR_VXIMZ | FPSCR_VXVC | FPSCR_VXSOFT | FPSCR_VXSQRT | FPSCR_VXCVI;
 
 const u32 FPSCR_ANY_X      = FPSCR_OX | FPSCR_UX | FPSCR_ZX | FPSCR_XX | FPSCR_VX_ANY;
 
 const u64 PPC_NAN_U64      = 0x7ff8000000000000ull;
 const double PPC_NAN       = *(double* const)&PPC_NAN_U64;
 
-inline bool IsINF(double x)
-{
-	return ((*(u64*)&x) & ~DOUBLE_SIGN) == DOUBLE_EXP;
-}
-
 inline void SetFPException(u32 mask)
 {
 	if ((FPSCR.Hex & mask) != mask)
+	{
 		FPSCR.FX = 1;
+	}
 	FPSCR.Hex |= mask;
 }
 
diff --git a/Source/UnitTests/Common/MathUtilTest.cpp b/Source/UnitTests/Common/MathUtilTest.cpp
index a6924f9cf7..56ade34522 100644
--- a/Source/UnitTests/Common/MathUtilTest.cpp
+++ b/Source/UnitTests/Common/MathUtilTest.cpp
@@ -2,8 +2,8 @@
 // Licensed under GPLv2
 // Refer to the license.txt file included.
 
-#include <cmath>
 #include <gtest/gtest.h>
+#include <limits>
 
 #include "Common/MathUtil.h"
 
@@ -27,19 +27,28 @@ TEST(MathUtil, Clamp)
 	EXPECT_EQ(0.0, ClampAndReturn(-1.0, 0.0, 2.0));
 }
 
+TEST(MathUtil, IsINF)
+{
+	EXPECT_TRUE(MathUtil::IsINF( std::numeric_limits<double>::infinity()));
+	EXPECT_TRUE(MathUtil::IsINF(-std::numeric_limits<double>::infinity()));
+}
+
 TEST(MathUtil, IsNAN)
 {
-	EXPECT_TRUE(MathUtil::IsNAN(nan("")));
+	EXPECT_TRUE(MathUtil::IsNAN(std::numeric_limits<double>::quiet_NaN()));
+	EXPECT_TRUE(MathUtil::IsNAN(std::numeric_limits<double>::signaling_NaN()));
 }
 
 TEST(MathUtil, IsQNAN)
 {
-	// TODO
+	EXPECT_TRUE(MathUtil::IsQNAN(std::numeric_limits<double>::quiet_NaN()));
+	EXPECT_FALSE(MathUtil::IsQNAN(std::numeric_limits<double>::signaling_NaN()));
 }
 
 TEST(MathUtil, IsSNAN)
 {
-	// TODO
+	EXPECT_FALSE(MathUtil::IsSNAN(std::numeric_limits<double>::quiet_NaN()));
+	EXPECT_TRUE(MathUtil::IsSNAN(std::numeric_limits<double>::signaling_NaN()));
 }
 
 TEST(MathUtil, Log2)