[dynarmic] Remove redundant constant pool ops

Signed-off-by: lizzie <lizzie@eden-emu.dev>

src/dynarmic/src/dynarmic/backend/x64/constant_pool.cpp

@@ -7,34 +7,27 @@
  */
 
 #include <cstring>
-
-#include "common/assert.h"
-
+#include <cassert>
 #include "dynarmic/backend/x64/block_of_code.h"
 #include "dynarmic/backend/x64/constant_pool.h"
 
 namespace Dynarmic::Backend::X64 {
 
-ConstantPool::ConstantPool(BlockOfCode& code, size_t size)
-    : insertion_point(0)
-{
-    code.EnsureMemoryCommitted(align_size + size);
-    code.int3();
+ConstantPool::ConstantPool(BlockOfCode& code, size_t size) noexcept {
+    auto const align_size = 64; //always align to cacheline
+    code.EnsureMemoryCommitted(2 * align_size + size);
     code.align(align_size);
-    pool = std::span<ConstantT>(reinterpret_cast<ConstantT*>(code.AllocateFromCodeSpace(size)), size / align_size);
+    pool = std::span<u128>(static_cast<u128*>(code.AllocateFromCodeSpace(size)), size / sizeof(u128));
 }
 
-Xbyak::Address ConstantPool::GetConstant(BlockOfCode& code, const Xbyak::AddressFrame& frame, u64 lower, u64 upper) {
-    const auto constant = ConstantT(lower, upper);
-    auto it = constant_info.find(constant);
-    if (it == constant_info.end()) {
-        ASSERT(insertion_point < pool.size());
-        ConstantT& target_constant = pool[insertion_point];
-        target_constant = constant;
-        it = constant_info.insert({constant, &target_constant}).first;
-        ++insertion_point;
-    }
-    return frame[code.rip + it->second];
+Xbyak::Address ConstantPool::GetConstant(BlockOfCode& code, const Xbyak::AddressFrame& frame, u64 lo, u64 hi) noexcept {
+    // offset grows iff new constant is added
+    auto const key = std::make_pair(lo, hi);
+    auto const val = u32(constant_info.size());
+    auto const [it, _] = constant_info.insert({key, val});
+    // if it != constant_info.end(): assume(pool[it->second] == c);
+    pool[it->second] = u128{lo, hi};
+    return frame[code.rip + std::addressof(pool[it->second])];
 }
 
 }  // namespace Dynarmic::Backend::X64

src/dynarmic/src/dynarmic/backend/x64/constant_pool.h

@@ -12,6 +12,7 @@
 #include <cstddef>
 #include <span>
 #include <utility>
+#include <boost/functional/hash.hpp>
 
 #include "common/common_types.h"
 #include "common/container/unordered_map.h"
@@ -21,31 +22,17 @@ namespace Dynarmic::Backend::X64 {
 
 class BlockOfCode;
 
-/// ConstantPool allocates a block of memory from BlockOfCode.
+/// @brief ConstantPool allocates a block of memory from BlockOfCode.
 /// It places constants into this block of memory, returning the address
 /// of the memory location where the constant is placed. If the constant
 /// already exists, its memory location is reused.
 class ConstantPool final {
 public:
-    ConstantPool(BlockOfCode& code, size_t size);
-
-    Xbyak::Address GetConstant(BlockOfCode& code, const Xbyak::AddressFrame& frame, u64 lower, u64 upper = 0);
-
-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 ConstantT& constant) const noexcept {
-            return constant.first ^ std::rotl<u64>(constant.second, 1);
-        }
-    };
-
-    ::Common::unordered_map<ConstantT, void*, ConstantHash> constant_info;
-    std::span<ConstantT> pool;
-    std::size_t insertion_point;
+    ConstantPool(BlockOfCode& code, size_t size) noexcept;
+    Xbyak::Address GetConstant(BlockOfCode& code, const Xbyak::AddressFrame& frame, u64 lower, u64 upper = 0) noexcept;
+    // key = identity hash, value = offset from pool.data()
+    ::Common::unordered_map<std::pair<u64, u64>, u32, boost::hash<std::pair<u64, u64>>> constant_info;
+    std::span<u128> pool;
 };
 
 }  // namespace Dynarmic::Backend::X64