common/fp/op: Add soft-float implementation of FPCompareEQ

This will be used to implement the half-precision floating-point
variants of FCMEQ in following changes.

src/CMakeLists.txt

@@ -24,6 +24,8 @@ add_library(dynarmic
     common/fp/info.h
     common/fp/mantissa_util.h
     common/fp/op.h
+    common/fp/op/FPCompare.cpp
+    common/fp/op/FPCompare.h
     common/fp/op/FPConvert.cpp
     common/fp/op/FPConvert.h
     common/fp/op/FPMulAdd.cpp

src/common/fp/op.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include "common/fp/op/FPCompare.h"
 #include "common/fp/op/FPConvert.h"
 #include "common/fp/op/FPMulAdd.h"
 #include "common/fp/op/FPRecipEstimate.h"

src/common/fp/op/FPCompare.cpp

@@ -0,0 +1,41 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2019 MerryMage
+ * This software may be used and distributed according to the terms of the GNU
+ * General Public License version 2 or any later version.
+ */
+
+#include "common/fp/fpcr.h"
+#include "common/fp/fpsr.h"
+#include "common/fp/op/FPCompare.h"
+#include "common/fp/process_exception.h"
+#include "common/fp/unpacked.h"
+
+namespace Dynarmic::FP {
+
+template <typename FPT>
+bool FPCompareEQ(FPT lhs, FPT rhs, FPCR fpcr, FPSR& fpsr) {
+    const auto unpacked1 = FPUnpack(lhs, fpcr, fpsr);
+    const auto unpacked2 = FPUnpack(rhs, fpcr, fpsr);
+    const auto type1 = std::get<FPType>(unpacked1);
+    const auto type2 = std::get<FPType>(unpacked2);
+    const auto& value1 = std::get<FPUnpacked>(unpacked1);
+    const auto& value2 = std::get<FPUnpacked>(unpacked2);
+
+    if (type1 == FPType::QNaN || type1 == FPType::SNaN ||
+        type2 == FPType::QNaN || type2 == FPType::SNaN) {
+        if (type1 == FPType::SNaN || type2 == FPType::SNaN) {
+            FPProcessException(FPExc::InvalidOp, fpcr, fpsr);
+        }
+
+        // Comparisons against NaN are never equal.
+        return false;
+    }
+
+    return value1 == value2 || (type1 == FPType::Zero && type2 == FPType::Zero);
+}
+
+template bool FPCompareEQ<u16>(u16 lhs, u16 rhs, FPCR fpcr, FPSR& fpsr);
+template bool FPCompareEQ<u32>(u32 lhs, u32 rhs, FPCR fpcr, FPSR& fpsr);
+template bool FPCompareEQ<u64>(u64 lhs, u64 rhs, FPCR fpcr, FPSR& fpsr);
+
+} // namespace Dynarmic::FP

src/common/fp/op/FPCompare.h

@@ -0,0 +1,17 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2019 MerryMage
+ * This software may be used and distributed according to the terms of the GNU
+ * General Public License version 2 or any later version.
+ */
+
+#pragma once
+
+namespace Dynarmic::FP {
+
+class FPCR;
+class FPSR;
+
+template <typename FPT>
+bool FPCompareEQ(FPT lhs, FPT rhs, FPCR fpcr, FPSR& fpsr);
+
+} // namespace Dynarmic::FP