From 6ffd71ffaefeb39066694eca9c4ea2cbea2a8dfd Mon Sep 17 00:00:00 2001
From: mitaclaw <140017135+mitaclaw@users.noreply.github.com>
Date: Mon, 24 Jun 2024 00:05:46 -0700
Subject: [PATCH] BitUtils: Constexpr BitCastToArray, Remove BitCastFromArray

`std::bit_cast` participates in overload resolution only if `sizeof(To) == sizeof(From)` and both `To` and `From` are *TriviallyCopyable* types, so the static assertions here can be removed. `[[nodiscard]]` was added as well.
---
 Source/Core/Common/BitUtils.h               | 47 ++-------------------
 Source/Core/Core/HW/DSPHLE/UCodes/AX.h      |  2 +-
 Source/Core/Core/HW/DSPHLE/UCodes/AXWii.cpp |  4 +-
 3 files changed, 7 insertions(+), 46 deletions(-)

diff --git a/Source/Core/Common/BitUtils.h b/Source/Core/Common/BitUtils.h
index b20baa20f2..8b1b196c24 100644
--- a/Source/Core/Common/BitUtils.h
+++ b/Source/Core/Common/BitUtils.h
@@ -4,6 +4,7 @@
 #pragma once
 
 #include <array>
+#include <bit>
 #include <climits>
 #include <cstddef>
 #include <cstdint>
@@ -166,50 +167,10 @@ inline auto BitCastPtr(PtrType* ptr) noexcept -> BitCastPtrType<T, PtrType>
 }
 
 // Similar to BitCastPtr, but specifically for aliasing structs to arrays.
-template <typename ArrayType, typename T,
-          typename Container = std::array<ArrayType, sizeof(T) / sizeof(ArrayType)>>
-inline auto BitCastToArray(const T& obj) noexcept -> Container
+template <typename ValueType, typename From>
+[[nodiscard]] constexpr auto BitCastToArray(const From& obj) noexcept
 {
-  static_assert(sizeof(T) % sizeof(ArrayType) == 0,
-                "Size of array type must be a factor of size of source type.");
-  static_assert(std::is_trivially_copyable<T>(),
-                "BitCastToArray source type must be trivially copyable.");
-  static_assert(std::is_trivially_copyable<Container>(),
-                "BitCastToArray array type must be trivially copyable.");
-
-  Container result;
-  std::memcpy(result.data(), &obj, sizeof(T));
-  return result;
-}
-
-template <typename ArrayType, typename T,
-          typename Container = std::array<ArrayType, sizeof(T) / sizeof(ArrayType)>>
-inline void BitCastFromArray(const Container& array, T& obj) noexcept
-{
-  static_assert(sizeof(T) % sizeof(ArrayType) == 0,
-                "Size of array type must be a factor of size of destination type.");
-  static_assert(std::is_trivially_copyable<Container>(),
-                "BitCastFromArray array type must be trivially copyable.");
-  static_assert(std::is_trivially_copyable<T>(),
-                "BitCastFromArray destination type must be trivially copyable.");
-
-  std::memcpy(&obj, array.data(), sizeof(T));
-}
-
-template <typename ArrayType, typename T,
-          typename Container = std::array<ArrayType, sizeof(T) / sizeof(ArrayType)>>
-inline auto BitCastFromArray(const Container& array) noexcept -> T
-{
-  static_assert(sizeof(T) % sizeof(ArrayType) == 0,
-                "Size of array type must be a factor of size of destination type.");
-  static_assert(std::is_trivially_copyable<Container>(),
-                "BitCastFromArray array type must be trivially copyable.");
-  static_assert(std::is_trivially_copyable<T>(),
-                "BitCastFromArray destination type must be trivially copyable.");
-
-  T obj;
-  std::memcpy(&obj, array.data(), sizeof(T));
-  return obj;
+  return std::bit_cast<std::array<ValueType, sizeof(From) / sizeof(ValueType)>>(obj);
 }
 
 template <typename T>
diff --git a/Source/Core/Core/HW/DSPHLE/UCodes/AX.h b/Source/Core/Core/HW/DSPHLE/UCodes/AX.h
index a4d8cb05f4..108a98e351 100644
--- a/Source/Core/Core/HW/DSPHLE/UCodes/AX.h
+++ b/Source/Core/Core/HW/DSPHLE/UCodes/AX.h
@@ -143,7 +143,7 @@ protected:
       pb_mem[update_off] = update_val;
     }
 
-    Common::BitCastFromArray<u16>(pb_mem, pb);
+    pb = std::bit_cast<PBType>(pb_mem);
   }
 
   virtual void HandleCommandList();
diff --git a/Source/Core/Core/HW/DSPHLE/UCodes/AXWii.cpp b/Source/Core/Core/HW/DSPHLE/UCodes/AXWii.cpp
index 36cd154f9b..53be74371d 100644
--- a/Source/Core/Core/HW/DSPHLE/UCodes/AXWii.cpp
+++ b/Source/Core/Core/HW/DSPHLE/UCodes/AXWii.cpp
@@ -397,7 +397,7 @@ bool AXWiiUCode::ExtractUpdatesFields(AXPBWii& pb, u16* num_updates, u16* update
   // Remove the updates data from the PB
   memmove(&pb_mem[41], &pb_mem[46], sizeof(pb) - 2 * 46);
 
-  Common::BitCastFromArray<u16>(pb_mem, pb);
+  pb = std::bit_cast<AXPBWii>(pb_mem);
 
   return true;
 }
@@ -416,7 +416,7 @@ void AXWiiUCode::ReinjectUpdatesFields(AXPBWii& pb, u16* num_updates, u32 update
   pb_mem[44] = updates_addr >> 16;
   pb_mem[45] = updates_addr & 0xFFFF;
 
-  Common::BitCastFromArray<u16>(pb_mem, pb);
+  pb = std::bit_cast<AXPBWii>(pb_mem);
 }
 
 void AXWiiUCode::ProcessPBList(u32 pb_addr)