From b168c2a9f9a67027dc311c8b30e4647f95b16df0 Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Sat, 2 Mar 2019 17:53:50 -0500
Subject: [PATCH] common/fp/op: Add operations for floating-point reciprocal
 exponents

---
 src/CMakeLists.txt                   |  2 +
 src/common/fp/op.h                   |  1 +
 src/common/fp/op/FPRecipExponent.cpp | 70 ++++++++++++++++++++++++++++
 src/common/fp/op/FPRecipExponent.h   | 17 +++++++
 4 files changed, 90 insertions(+)
 create mode 100644 src/common/fp/op/FPRecipExponent.cpp
 create mode 100644 src/common/fp/op/FPRecipExponent.h

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index c6a51f87..cfb45452 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -28,6 +28,8 @@ add_library(dynarmic
     common/fp/op/FPMulAdd.h
     common/fp/op/FPRecipEstimate.cpp
     common/fp/op/FPRecipEstimate.h
+    common/fp/op/FPRecipExponent.cpp
+    common/fp/op/FPRecipExponent.h
     common/fp/op/FPRecipStepFused.cpp
     common/fp/op/FPRecipStepFused.h
     common/fp/op/FPRoundInt.cpp
diff --git a/src/common/fp/op.h b/src/common/fp/op.h
index f7232407..c792e50e 100644
--- a/src/common/fp/op.h
+++ b/src/common/fp/op.h
@@ -8,6 +8,7 @@
 
 #include "common/fp/op/FPMulAdd.h"
 #include "common/fp/op/FPRecipEstimate.h"
+#include "common/fp/op/FPRecipExponent.h"
 #include "common/fp/op/FPRecipStepFused.h"
 #include "common/fp/op/FPRoundInt.h"
 #include "common/fp/op/FPRSqrtEstimate.h"
diff --git a/src/common/fp/op/FPRecipExponent.cpp b/src/common/fp/op/FPRecipExponent.cpp
new file mode 100644
index 00000000..eaa7addb
--- /dev/null
+++ b/src/common/fp/op/FPRecipExponent.cpp
@@ -0,0 +1,70 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2018 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 <tuple>
+
+#include "common/common_types.h"
+#include "common/bit_util.h"
+#include "common/fp/fpcr.h"
+#include "common/fp/fpsr.h"
+#include "common/fp/info.h"
+#include "common/fp/op/FPRecipExponent.h"
+#include "common/fp/process_nan.h"
+#include "common/fp/unpacked.h"
+
+namespace Dynarmic::FP {
+namespace {
+// We don't care about unreachable code warnings here
+// TODO: Remove this warning disabling of warnings when
+// half-float support is added.
+#ifdef _MSC_VER
+#pragma warning(disable:4702)
+#endif
+template <typename FPT>
+FPT DetermineExponentValue(size_t value) {
+    if constexpr (sizeof(FPT) == sizeof(u32)) {
+        return static_cast<FPT>(Common::Bits<23, 30>(value));
+    }
+
+    if constexpr (sizeof(FPT) == sizeof(u64)) {
+        return static_cast<FPT>(Common::Bits<52, 62>(value));
+    }
+
+    // Half-float
+    return static_cast<FPT>(Common::Bits<10, 14>(value));
+}
+#ifdef _MSC_VER
+#pragma warning(default:4702)
+#endif
+} // Anonymous namespace
+
+template <typename FPT>
+FPT FPRecipExponent(FPT op, FPCR fpcr, FPSR& fpsr) {
+    const auto [type, sign, value] = FPUnpack<FPT>(op, fpcr, fpsr);
+    (void)value;
+
+    if (type == FPType::SNaN || type == FPType::QNaN) {
+        return FPProcessNaN(type, op, fpcr, fpsr);
+    }
+
+    const FPT sign_bits = FPInfo<FPT>::Zero(sign);
+    const FPT exponent = DetermineExponentValue<FPT>(op);
+
+    // Zero and denormals
+    if (exponent == 0) {
+        const FPT max_exponent = Common::Ones<FPT>(FPInfo<FPT>::exponent_width) - 1;
+        return FPT(sign_bits | (max_exponent << FPInfo<FPT>::explicit_mantissa_width));
+    }
+
+    // Infinities and normals
+    const auto negated_exponent = (~exponent << FPInfo<FPT>::explicit_mantissa_width) & FPInfo<FPT>::exponent_mask;
+    return FPT(sign_bits | negated_exponent);
+}
+
+template u32 FPRecipExponent<u32>(u32 op, FPCR fpcr, FPSR& fpsr);
+template u64 FPRecipExponent<u64>(u64 op, FPCR fpcr, FPSR& fpsr);
+
+} // namespace Dynarmic::FP
diff --git a/src/common/fp/op/FPRecipExponent.h b/src/common/fp/op/FPRecipExponent.h
new file mode 100644
index 00000000..285d0e9d
--- /dev/null
+++ b/src/common/fp/op/FPRecipExponent.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>
+FPT FPRecipExponent(FPT op, FPCR fpcr, FPSR& fpsr);
+
+} // namespace Dynarmic::FP