From a5318c775c2dd817cb857ea4e459f0e2bbe5c3a6 Mon Sep 17 00:00:00 2001
From: Wunkolo <Wunkolo@gmail.com>
Date: Tue, 28 Jun 2022 11:58:17 -0700
Subject: [PATCH] constant_pool: Use `std::span` to manage pool

Simplifies some raw pointer arithmetic and type-usage into the new
`ConstantT` type.
---
 src/dynarmic/backend/x64/constant_pool.cpp | 18 +++++++++---------
 src/dynarmic/backend/x64/constant_pool.h   | 14 +++++++++-----
 2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/src/dynarmic/backend/x64/constant_pool.cpp b/src/dynarmic/backend/x64/constant_pool.cpp
index 14e37f67..29678847 100644
--- a/src/dynarmic/backend/x64/constant_pool.cpp
+++ b/src/dynarmic/backend/x64/constant_pool.cpp
@@ -14,22 +14,22 @@
 namespace Dynarmic::Backend::X64 {
 
 ConstantPool::ConstantPool(BlockOfCode& code, size_t size)
-        : code(code), pool_size(size) {
+        : code(code), insertion_point(0) {
     code.int3();
     code.align(align_size);
-    pool_begin = reinterpret_cast<u8*>(code.AllocateFromCodeSpace(size));
-    current_pool_ptr = pool_begin;
+    pool = std::span<ConstantT>(
+        reinterpret_cast<ConstantT*>(code.AllocateFromCodeSpace(size)), size / align_size);
 }
 
 Xbyak::Address ConstantPool::GetConstant(const Xbyak::AddressFrame& frame, u64 lower, u64 upper) {
-    const auto constant = std::make_pair(lower, upper);
+    const auto constant = ConstantT(lower, upper);
     auto iter = constant_info.find(constant);
     if (iter == constant_info.end()) {
-        ASSERT(static_cast<size_t>(current_pool_ptr - pool_begin) < pool_size);
-        std::memcpy(current_pool_ptr, &lower, sizeof(u64));
-        std::memcpy(current_pool_ptr + sizeof(u64), &upper, sizeof(u64));
-        iter = constant_info.emplace(constant, current_pool_ptr).first;
-        current_pool_ptr += align_size;
+        ASSERT(insertion_point < pool.size());
+        ConstantT& target_constant = pool[insertion_point];
+        target_constant = constant;
+        iter = constant_info.emplace(constant, &target_constant).first;
+        ++insertion_point;
     }
     return frame[code.rip + iter->second];
 }
diff --git a/src/dynarmic/backend/x64/constant_pool.h b/src/dynarmic/backend/x64/constant_pool.h
index 3a5717e9..2ab64215 100644
--- a/src/dynarmic/backend/x64/constant_pool.h
+++ b/src/dynarmic/backend/x64/constant_pool.h
@@ -6,6 +6,8 @@
 #pragma once
 
 #include <bit>
+#include <cstddef>
+#include <span>
 #include <utility>
 
 #include <mcl/stdint.hpp>
@@ -29,18 +31,20 @@ public:
 private:
     static constexpr size_t align_size = 16;  // bytes
 
+    using ConstantT = std::pair<u64, u64>;
+    static_assert(sizeof(ConstantT) == align_size);
+
     struct ConstantHash {
-        std::size_t operator()(const std::pair<u64, u64>& constant) const noexcept {
+        std::size_t operator()(const ConstantT& constant) const noexcept {
             return constant.first ^ std::rotl<u64>(constant.second, 1);
         }
     };
 
-    tsl::robin_map<std::pair<u64, u64>, void*, ConstantHash> constant_info;
+    tsl::robin_map<ConstantT, void*, ConstantHash> constant_info;
 
     BlockOfCode& code;
-    size_t pool_size;
-    u8* pool_begin;
-    u8* current_pool_ptr;
+    std::span<ConstantT> pool;
+    std::size_t insertion_point;
 };
 
 }  // namespace Dynarmic::Backend::X64