From 95af9dafbe3532f9fe7f7aa319607159ebf91d9d Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Sun, 3 Mar 2019 01:08:12 -0500
Subject: [PATCH] common/fp/op: Add FP conversion functions

---
 src/CMakeLists.txt             |   2 +
 src/common/fp/op.h             |   1 +
 src/common/fp/op/FPConvert.cpp | 102 +++++++++++++++++++++++++++++++++
 src/common/fp/op/FPConvert.h   |  18 ++++++
 4 files changed, 123 insertions(+)
 create mode 100644 src/common/fp/op/FPConvert.cpp
 create mode 100644 src/common/fp/op/FPConvert.h

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index c9ef4fcb..66c1db77 100644
--- a/src/CMakeLists.txt
+++ b/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/FPConvert.cpp
+    common/fp/op/FPConvert.h
     common/fp/op/FPMulAdd.cpp
     common/fp/op/FPMulAdd.h
     common/fp/op/FPRecipEstimate.cpp
diff --git a/src/common/fp/op.h b/src/common/fp/op.h
index c792e50e..b8ee1441 100644
--- a/src/common/fp/op.h
+++ b/src/common/fp/op.h
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include "common/fp/op/FPConvert.h"
 #include "common/fp/op/FPMulAdd.h"
 #include "common/fp/op/FPRecipEstimate.h"
 #include "common/fp/op/FPRecipExponent.h"
diff --git a/src/common/fp/op/FPConvert.cpp b/src/common/fp/op/FPConvert.cpp
new file mode 100644
index 00000000..559d0242
--- /dev/null
+++ b/src/common/fp/op/FPConvert.cpp
@@ -0,0 +1,102 @@
+/* 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 <tuple>
+
+#include "common/common_types.h"
+#include "common/fp/fpcr.h"
+#include "common/fp/fpsr.h"
+#include "common/fp/info.h"
+#include "common/fp/op/FPRecipEstimate.h"
+#include "common/fp/process_exception.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 disabling of warnings when
+// half-float support is added.
+#ifdef _MSC_VER
+#pragma warning(disable:4702)
+#endif
+template <typename FPT_TO, typename FPT_FROM>
+FPT_TO FPConvertNaN(FPT_FROM op) {
+    const bool sign = Common::Bit<Common::BitSize<FPT_FROM>() - 1>(op);
+    const u64 frac = [op] {
+        if constexpr (sizeof(FPT_FROM) == sizeof(u64)) {
+            return Common::Bits<0, 50>(op);
+        }
+
+        if constexpr (sizeof(FPT_FROM) == sizeof(u32)) {
+            return u64{Common::Bits<0, 21>(op)} << 29;
+        }
+
+        return u64{Common::Bits<0, 8>(op)} << 42;
+    }();
+
+    const size_t dest_bit_size = Common::BitSize<FPT_TO>();
+    const u64 shifted_sign = u64{sign} << (dest_bit_size - 1);
+    const u64 exponent = Common::Ones<u64>(dest_bit_size - FPInfo<FPT_TO>::explicit_mantissa_width);
+
+    if constexpr (sizeof(FPT_TO) == sizeof(u64)) {
+        return FPT_TO(shifted_sign | exponent << 52 | frac);
+    }
+
+    if constexpr (sizeof(FPT_TO) == sizeof(u32)) {
+        return FPT_TO(shifted_sign | exponent << 22 | Common::Bits<29, 50>(frac));
+    }
+
+    return FPT_TO(shifted_sign | exponent << 9 | Common::Bits<42, 50>(frac));
+}
+#ifdef _MSC_VER
+#pragma warning(default:4702)
+#endif
+} // Anonymous namespace
+
+template <typename FPT_TO, typename FPT_FROM>
+FPT_TO FPConvert(FPT_FROM op, FPCR fpcr, RoundingMode rounding_mode, FPSR& fpsr) {
+    const auto [type, sign, value] = FPUnpack<FPT_FROM>(op, fpcr, fpsr);
+    const bool is_althp = Common::BitSize<FPT_TO>() == 16 && fpcr.AHP();
+
+    if (type == FPType::SNaN || type == FPType::QNaN) {
+        FPT_TO result{};
+
+        if (is_althp) {
+            result = FPInfo<FPT_TO>::Zero(sign);
+        } else if (fpcr.DN()) {
+            result = FPInfo<FPT_TO>::DefaultNaN();
+        } else {
+            result = FPConvertNaN<FPT_TO>(op);
+        }
+
+        if (type == FPType::SNaN || is_althp) {
+            FPProcessException(FPExc::InvalidOp, fpcr, fpsr);
+        }
+
+        return result;
+    }
+
+    if (type == FPType::Infinity) {
+        if (is_althp) {
+            FPProcessException(FPExc::InvalidOp, fpcr, fpsr);
+            return static_cast<FPT_TO>(u32{sign} << 15 | 0b111111111111111);
+        }
+
+        return FPInfo<FPT_TO>::Infinity(sign);
+    }
+
+    if (type == FPType::Zero) {
+        return FPInfo<FPT_TO>::Zero(sign);
+    }
+
+    return FPRoundBase<FPT_TO>(value, fpcr, rounding_mode, fpsr);
+}
+
+template u64 FPConvert<u64, u32>(u32 op, FPCR fpcr, RoundingMode rounding_mode, FPSR& fpsr);
+template u32 FPConvert<u32, u64>(u64 op, FPCR fpcr, RoundingMode rounding_mode, FPSR& fpsr);
+
+} // namespace Dynarmic::FP
diff --git a/src/common/fp/op/FPConvert.h b/src/common/fp/op/FPConvert.h
new file mode 100644
index 00000000..419a158b
--- /dev/null
+++ b/src/common/fp/op/FPConvert.h
@@ -0,0 +1,18 @@
+/* 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;
+enum class RoundingMode;
+
+template <typename FPT_TO, typename FPT_FROM>
+FPT_TO FPConvert(FPT_FROM op, FPCR fpcr, RoundingMode rounding_mode, FPSR& fpsr);
+
+} // namespace Dynarmic::FP