backend/rv64: Initial implementation of register allocator

src/dynarmic/CMakeLists.txt

@@ -402,6 +402,16 @@ endif()
 if ("riscv" IN_LIST ARCHITECTURE)
     target_link_libraries(dynarmic PRIVATE biscuit::biscuit)
 
+    target_sources(dynarmic PRIVATE
+        backend/riscv64/abi.h
+        backend/riscv64/emit_context.h
+        backend/riscv64/emit_riscv64.cpp
+        backend/riscv64/emit_riscv64.h
+        backend/riscv64/reg_alloc.cpp
+        backend/riscv64/reg_alloc.h
+        backend/riscv64/stack_layout.h
+    )
+
     if ("A32" IN_LIST DYNARMIC_FRONTENDS)
         target_sources(dynarmic PRIVATE
             backend/riscv64/a32_address_space.cpp
@@ -411,8 +421,6 @@ if ("riscv" IN_LIST ARCHITECTURE)
             backend/riscv64/a32_jitstate.cpp
             backend/riscv64/a32_jitstate.h
             backend/riscv64/code_block.h
-            backend/riscv64/emit_riscv64.cpp
-            backend/riscv64/emit_riscv64.h
         )
     endif()
 

src/dynarmic/backend/riscv64/a32_address_space.cpp

@@ -7,6 +7,7 @@
 
 #include <mcl/assert.hpp>
 
+#include "dynarmic/backend/riscv64/abi.h"
 #include "dynarmic/backend/riscv64/emit_riscv64.h"
 #include "dynarmic/frontend/A32/a32_location_descriptor.h"
 #include "dynarmic/frontend/A32/translate/a32_translate.h"
@@ -80,6 +81,8 @@ void A32AddressSpace::EmitPrelude() {
         as.FSD(FPR{i}, 32 + i * 8, sp);
     }
 
+    as.ADDI(Xstate, a1, 0);
+    as.ADDI(Xhalt, a2, 0);
     as.JALR(x0, 0, a0);
 
     prelude_info.return_from_run_code = GetCursorPtr<CodePtr>();
@@ -112,7 +115,7 @@ EmittedBlockInfo A32AddressSpace::Emit(IR::Block block) {
         ClearCache();
     }
 
-    EmittedBlockInfo block_info = EmitRV64(as, std::move(block));
+    EmittedBlockInfo block_info = EmitRV64(as, std::move(block), {});
     Link(block_info);
 
     return block_info;

src/dynarmic/backend/riscv64/abi.h

@@ -0,0 +1,20 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2024 MerryMage
+ * SPDX-License-Identifier: 0BSD
+ */
+
+#pragma once
+
+#include <biscuit/registers.hpp>
+
+namespace Dynarmic::Backend::RV64 {
+
+constexpr biscuit::GPR Xstate{27};
+constexpr biscuit::GPR Xhalt{26};
+
+constexpr biscuit::GPR Xscratch0{30}, Xscratch1{31};
+
+constexpr std::initializer_list<u32> GPR_ORDER{8, 9, 18, 19, 20, 21, 22, 23, 24, 25, 5, 6, 7, 28, 29, 10, 11, 12, 13, 14, 15, 16, 17};
+constexpr std::initializer_list<u32> FPR_ORDER{8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31};
+
+}  // namespace Dynarmic::Backend::RV64

src/dynarmic/backend/riscv64/emit_context.h

@@ -0,0 +1,26 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2024 MerryMage
+ * SPDX-License-Identifier: 0BSD
+ */
+
+#pragma once
+
+#include "dynarmic/backend/riscv64/emit_riscv64.h"
+#include "dynarmic/backend/riscv64/reg_alloc.h"
+
+namespace Dynarmic::IR {
+class Block;
+}  // namespace Dynarmic::IR
+
+namespace Dynarmic::Backend::RV64 {
+
+struct EmitConfig;
+
+struct EmitContext {
+    IR::Block& block;
+    RegAlloc& reg_alloc;
+    const EmitConfig& emit_conf;
+    EmittedBlockInfo& ebi;
+};
+
+}  // namespace Dynarmic::Backend::RV64

src/dynarmic/backend/riscv64/emit_riscv64.cpp

@@ -5,25 +5,98 @@
 
 #include "dynarmic/backend/riscv64/emit_riscv64.h"
 
+#include <bit>
+
 #include <biscuit/assembler.hpp>
+#include <fmt/ostream.h>
+#include <mcl/bit/bit_field.hpp>
 
 #include "dynarmic/backend/riscv64/a32_jitstate.h"
+#include "dynarmic/backend/riscv64/abi.h"
+#include "dynarmic/backend/riscv64/emit_context.h"
+#include "dynarmic/backend/riscv64/reg_alloc.h"
 #include "dynarmic/ir/basic_block.h"
+#include "dynarmic/ir/microinstruction.h"
+#include "dynarmic/ir/opcodes.h"
 
 namespace Dynarmic::Backend::RV64 {
 
-EmittedBlockInfo EmitRV64(biscuit::Assembler& as, [[maybe_unused]] IR::Block block) {
+// TODO: We should really move this to biscuit.
+static void Mov64(biscuit::Assembler& as, biscuit::GPR rd, u64 imm) {
+    if (mcl::bit::sign_extend<32>(imm) == imm) {
+        as.LI(rd, static_cast<u32>(imm));
+        return;
+    }
+
+    // For 64-bit imm, a sequence of up to 8 instructions (i.e. LUI+ADDIW+SLLI+ADDI+SLLI+ADDI+SLLI+ADDI) is emitted.
+    // In the following, imm is processed from LSB to MSB while instruction emission is performed from MSB to LSB by calling Mov64 recursively.
+    // In each recursion, the lowest 12 bits are removed from imm and the optimal shift amount is calculated.
+    // Then, the remaining part of imm is processed recursively and as.LI() get called as soon as it fits into 32 bits.
+    s32 lo12 = static_cast<s32>(mcl::bit::sign_extend<12>(imm));
+    /* Add 0x800 to cancel out the signed extension of ADDI. */
+    u64 hi52 = (imm + 0x800) >> 12;
+    int shift = 12 + std::countr_zero(hi52);
+    hi52 = mcl::bit::sign_extend(shift, hi52 >> (shift - 12));
+    Mov64(as, rd, hi52);
+    as.SLLI(rd, rd, shift);
+    if (lo12 != 0) {
+        as.ADDI(rd, rd, lo12);
+    }
+}
+
+template<IR::Opcode op>
+void EmitIR(biscuit::Assembler&, EmitContext&, IR::Inst*) {
+    ASSERT_FALSE("Unimplemented opcode {}", op);
+}
+
+template<>
+void EmitIR<IR::Opcode::GetCarryFromOp>(biscuit::Assembler&, EmitContext& ctx, IR::Inst* inst) {
+    ASSERT(ctx.reg_alloc.IsValueLive(inst));
+}
+
+EmittedBlockInfo EmitRV64(biscuit::Assembler& as, IR::Block block, const EmitConfig& emit_conf) {
     using namespace biscuit;
 
     EmittedBlockInfo ebi;
+
+    RegAlloc reg_alloc{as, GPR_ORDER, FPR_ORDER};
+    EmitContext ctx{block, reg_alloc, emit_conf, ebi};
+
     ebi.entry_point = reinterpret_cast<CodePtr>(as.GetCursorPointer());
 
-    as.ADDIW(a0, zero, 8);
-    as.SW(a0, offsetof(A32JitState, regs) + 0 * sizeof(u32), a1);
+    for (auto iter = block.begin(); iter != block.end(); ++iter) {
+        IR::Inst* inst = &*iter;
 
-    as.ADDIW(a0, zero, 2);
-    as.SW(a0, offsetof(A32JitState, regs) + 1 * sizeof(u32), a1);
-    as.SW(a0, offsetof(A32JitState, regs) + 15 * sizeof(u32), a1);
+        switch (inst->GetOpcode()) {
+#define OPCODE(name, type, ...)                  \
+    case IR::Opcode::name:                       \
+        EmitIR<IR::Opcode::name>(as, ctx, inst); \
+        break;
+#define A32OPC(name, type, ...)                       \
+    case IR::Opcode::A32##name:                       \
+        EmitIR<IR::Opcode::A32##name>(as, ctx, inst); \
+        break;
+#define A64OPC(name, type, ...)                       \
+    case IR::Opcode::A64##name:                       \
+        EmitIR<IR::Opcode::A64##name>(as, ctx, inst); \
+        break;
+#include "dynarmic/ir/opcodes.inc"
+#undef OPCODE
+#undef A32OPC
+#undef A64OPC
+        default:
+            ASSERT_FALSE("Invalid opcode: {}", inst->GetOpcode());
+            break;
+        }
+    }
+    // TODO: Add Cycles
+
+    // TODO: Emit Terminal
+    const auto term = block.GetTerminal();
+    const IR::Term::LinkBlock* link_block_term = boost::get<IR::Term::LinkBlock>(&term);
+    ASSERT(link_block_term);
+    Mov64(as, Xscratch0, link_block_term->next.Value());
+    as.SD(Xscratch0, offsetof(A32JitState, regs) + sizeof(u32) * 15, Xstate);
 
     ptrdiff_t offset = reinterpret_cast<CodePtr>(as.GetCursorPointer()) - ebi.entry_point;
     ebi.relocations.emplace_back(Relocation{offset, LinkTarget::ReturnFromRunCode});

src/dynarmic/backend/riscv64/emit_riscv64.h

@@ -15,6 +15,8 @@ class Assembler;
 
 namespace Dynarmic::IR {
 class Block;
+enum class Opcode;
+class Inst;
 }  // namespace Dynarmic::IR
 
 namespace Dynarmic::Backend::RV64 {
@@ -36,6 +38,13 @@ struct EmittedBlockInfo {
     std::vector<Relocation> relocations;
 };
 
-EmittedBlockInfo EmitRV64(biscuit::Assembler& as, IR::Block block);
+struct EmitConfig {};
+
+struct EmitContext;
+
+template<IR::Opcode op>
+void EmitIR(biscuit::Assembler& as, EmitContext& ctx, IR::Inst* inst);
+
+EmittedBlockInfo EmitRV64(biscuit::Assembler& as, IR::Block block, const EmitConfig& emit_conf);
 
 }  // namespace Dynarmic::Backend::RV64

src/dynarmic/backend/riscv64/reg_alloc.cpp

@@ -0,0 +1,280 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2024 MerryMage
+ * SPDX-License-Identifier: 0BSD
+ */
+
+#include "dynarmic/backend/riscv64/reg_alloc.h"
+
+#include <algorithm>
+#include <array>
+
+#include <mcl/assert.hpp>
+#include <mcl/stdint.hpp>
+
+namespace Dynarmic::Backend::RV64 {
+
+constexpr size_t spill_offset = offsetof(StackLayout, spill);
+constexpr size_t spill_slot_size = sizeof(decltype(StackLayout::spill)::value_type);
+
+static bool IsValuelessType(IR::Type type) {
+    switch (type) {
+    case IR::Type::Table:
+        return true;
+    default:
+        return false;
+    }
+}
+
+IR::Type Argument::GetType() const {
+    return value.GetType();
+}
+
+bool Argument::IsImmediate() const {
+    return value.IsImmediate();
+}
+
+bool Argument::GetImmediateU1() const {
+    return value.GetU1();
+}
+
+u8 Argument::GetImmediateU8() const {
+    const u64 imm = value.GetImmediateAsU64();
+    ASSERT(imm < 0x100);
+    return u8(imm);
+}
+
+u16 Argument::GetImmediateU16() const {
+    const u64 imm = value.GetImmediateAsU64();
+    ASSERT(imm < 0x10000);
+    return u16(imm);
+}
+
+u32 Argument::GetImmediateU32() const {
+    const u64 imm = value.GetImmediateAsU64();
+    ASSERT(imm < 0x100000000);
+    return u32(imm);
+}
+
+u64 Argument::GetImmediateU64() const {
+    return value.GetImmediateAsU64();
+}
+
+IR::Cond Argument::GetImmediateCond() const {
+    ASSERT(IsImmediate() && GetType() == IR::Type::Cond);
+    return value.GetCond();
+}
+
+IR::AccType Argument::GetImmediateAccType() const {
+    ASSERT(IsImmediate() && GetType() == IR::Type::AccType);
+    return value.GetAccType();
+}
+
+bool HostLocInfo::Contains(const IR::Inst* value) const {
+    return std::find(values.begin(), values.end(), value) != values.end();
+}
+
+RegAlloc::ArgumentInfo RegAlloc::GetArgumentInfo(IR::Inst* inst) {
+    ArgumentInfo ret = {Argument{*this}, Argument{*this}, Argument{*this}, Argument{*this}};
+    for (size_t i = 0; i < inst->NumArgs(); i++) {
+        const IR::Value arg = inst->GetArg(i);
+        ret[i].value = arg;
+        if (!arg.IsImmediate() && !IsValuelessType(arg.GetType())) {
+            ASSERT_MSG(ValueLocation(arg.GetInst()), "argument must already been defined");
+            ValueInfo(arg.GetInst()).accumulated_uses++;
+        }
+    }
+    return ret;
+}
+
+bool RegAlloc::IsValueLive(IR::Inst* inst) const {
+    return !!ValueLocation(inst);
+}
+
+template<bool is_fpr>
+u32 RegAlloc::RealizeReadImpl(const IR::Inst* value) {
+    constexpr HostLoc::Kind required_kind = is_fpr ? HostLoc::Kind::Fpr : HostLoc::Kind::Gpr;
+
+    const auto current_location = ValueLocation(value);
+    ASSERT(current_location);
+
+    if (current_location->kind == required_kind) {
+        ValueInfo(*current_location).realized = true;
+        return current_location->index;
+    }
+
+    ASSERT(!ValueInfo(*current_location).realized);
+    ASSERT(!ValueInfo(*current_location).locked);
+
+    if constexpr (is_fpr) {
+        const u32 new_location_index = AllocateRegister(fprs, fpr_order);
+        SpillFpr(new_location_index);
+
+        switch (current_location->kind) {
+        case HostLoc::Kind::Gpr:
+            as.FMV_D_X(biscuit::FPR{new_location_index}, biscuit::GPR(current_location->index));
+            break;
+        case HostLoc::Kind::Fpr:
+            ASSERT_FALSE("Logic error");
+            break;
+        case HostLoc::Kind::Spill:
+            as.FLD(biscuit::FPR{new_location_index}, spill_offset + new_location_index * spill_slot_size, biscuit::sp);
+            break;
+        }
+
+        fprs[new_location_index] = std::exchange(ValueInfo(*current_location), {});
+        fprs[new_location_index].realized = true;
+        return new_location_index;
+    } else {
+        const u32 new_location_index = AllocateRegister(gprs, gpr_order);
+        SpillGpr(new_location_index);
+
+        switch (current_location->kind) {
+        case HostLoc::Kind::Gpr:
+            ASSERT_FALSE("Logic error");
+            break;
+        case HostLoc::Kind::Fpr:
+            as.FMV_X_D(biscuit::GPR(new_location_index), biscuit::FPR{current_location->index});
+            // ASSERT size fits
+            break;
+        case HostLoc::Kind::Spill:
+            as.LD(biscuit::GPR{new_location_index}, spill_offset + new_location_index * spill_slot_size, biscuit::sp);
+            break;
+        }
+
+        gprs[new_location_index] = std::exchange(ValueInfo(*current_location), {});
+        gprs[new_location_index].realized = true;
+        return new_location_index;
+    }
+}
+
+template<bool is_fpr>
+u32 RegAlloc::RealizeWriteImpl(const IR::Inst* value) {
+    ASSERT(!ValueLocation(value));
+
+    const auto setup_location = [&](HostLocInfo& info) {
+        info = {};
+        info.values.emplace_back(value);
+        info.locked = true;
+        info.realized = true;
+        info.expected_uses += value->UseCount();
+    };
+
+    if constexpr (is_fpr) {
+        const u32 new_location_index = AllocateRegister(fprs, fpr_order);
+        SpillFpr(new_location_index);
+        setup_location(fprs[new_location_index]);
+        return new_location_index;
+    } else {
+        const u32 new_location_index = AllocateRegister(gprs, gpr_order);
+        SpillGpr(new_location_index);
+        setup_location(gprs[new_location_index]);
+        return new_location_index;
+    }
+}
+
+template u32 RegAlloc::RealizeReadImpl<true>(const IR::Inst* value);
+template u32 RegAlloc::RealizeReadImpl<false>(const IR::Inst* value);
+template u32 RegAlloc::RealizeWriteImpl<true>(const IR::Inst* value);
+template u32 RegAlloc::RealizeWriteImpl<false>(const IR::Inst* value);
+
+void RegAlloc::Unlock(HostLoc host_loc) {
+    HostLocInfo& info = ValueInfo(host_loc);
+    if (!info.realized) {
+        return;
+    }
+
+    if (info.accumulated_uses == info.expected_uses) {
+        info = {};
+    } else {
+        info.realized = false;
+        info.locked = false;
+    }
+}
+
+u32 RegAlloc::AllocateRegister(const std::array<HostLocInfo, 32>& regs, const std::vector<u32>& order) const {
+    const auto empty = std::find_if(order.begin(), order.end(), [&](u32 i) { return regs[i].values.empty() && !regs[i].locked; });
+    if (empty != order.end()) {
+        return *empty;
+    }
+
+    std::vector<u32> candidates;
+    std::copy_if(order.begin(), order.end(), std::back_inserter(candidates), [&](u32 i) { return !regs[i].locked; });
+
+    // TODO: LRU
+    std::uniform_int_distribution<size_t> dis{0, candidates.size() - 1};
+    return candidates[dis(rand_gen)];
+}
+
+void RegAlloc::SpillGpr(u32 index) {
+    ASSERT(!gprs[index].locked && !gprs[index].realized);
+    if (gprs[index].values.empty()) {
+        return;
+    }
+    const u32 new_location_index = FindFreeSpill();
+    as.SD(biscuit::GPR{index}, spill_offset + new_location_index * spill_slot_size, biscuit::sp);
+    spills[new_location_index] = std::exchange(gprs[index], {});
+}
+
+void RegAlloc::SpillFpr(u32 index) {
+    ASSERT(!fprs[index].locked && !fprs[index].realized);
+    if (fprs[index].values.empty()) {
+        return;
+    }
+    const u32 new_location_index = FindFreeSpill();
+    as.FSD(biscuit::FPR{index}, spill_offset + new_location_index * spill_slot_size, biscuit::sp);
+    spills[new_location_index] = std::exchange(fprs[index], {});
+}
+
+u32 RegAlloc::FindFreeSpill() const {
+    const auto iter = std::find_if(spills.begin(), spills.end(), [](const HostLocInfo& info) { return info.values.empty(); });
+    ASSERT_MSG(iter != spills.end(), "All spill locations are full");
+    return static_cast<u32>(iter - spills.begin());
+}
+
+std::optional<HostLoc> RegAlloc::ValueLocation(const IR::Inst* value) const {
+    const auto contains_value = [value](const HostLocInfo& info) {
+        return info.Contains(value);
+    };
+
+    if (const auto iter = std::find_if(gprs.begin(), gprs.end(), contains_value); iter != gprs.end()) {
+        return HostLoc{HostLoc::Kind::Gpr, static_cast<u32>(iter - gprs.begin())};
+    }
+    if (const auto iter = std::find_if(fprs.begin(), fprs.end(), contains_value); iter != fprs.end()) {
+        return HostLoc{HostLoc::Kind::Fpr, static_cast<u32>(iter - fprs.begin())};
+    }
+    if (const auto iter = std::find_if(spills.begin(), spills.end(), contains_value); iter != spills.end()) {
+        return HostLoc{HostLoc::Kind::Spill, static_cast<u32>(iter - spills.begin())};
+    }
+    return std::nullopt;
+}
+
+HostLocInfo& RegAlloc::ValueInfo(HostLoc host_loc) {
+    switch (host_loc.kind) {
+    case HostLoc::Kind::Gpr:
+        return gprs[static_cast<size_t>(host_loc.index)];
+    case HostLoc::Kind::Fpr:
+        return fprs[static_cast<size_t>(host_loc.index)];
+    case HostLoc::Kind::Spill:
+        return spills[static_cast<size_t>(host_loc.index)];
+    }
+    ASSERT_FALSE("RegAlloc::ValueInfo: Invalid HostLoc::Kind");
+}
+
+HostLocInfo& RegAlloc::ValueInfo(const IR::Inst* value) {
+    const auto contains_value = [value](const HostLocInfo& info) {
+        return info.Contains(value);
+    };
+
+    if (const auto iter = std::find_if(gprs.begin(), gprs.end(), contains_value)) {
+        return *iter;
+    }
+    if (const auto iter = std::find_if(fprs.begin(), fprs.end(), contains_value)) {
+        return *iter;
+    }
+    if (const auto iter = std::find_if(spills.begin(), spills.end(), contains_value)) {
+        return *iter;
+    }
+    ASSERT_FALSE("RegAlloc::ValueInfo: Value not found");
+}
+
+}  // namespace Dynarmic::Backend::RV64

src/dynarmic/backend/riscv64/reg_alloc.h

@@ -0,0 +1,169 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2024 MerryMage
+ * SPDX-License-Identifier: 0BSD
+ */
+
+#pragma once
+
+#include <array>
+#include <optional>
+#include <random>
+#include <utility>
+#include <vector>
+
+#include <biscuit/assembler.hpp>
+#include <biscuit/registers.hpp>
+#include <mcl/assert.hpp>
+#include <mcl/stdint.hpp>
+#include <mcl/type_traits/is_instance_of_template.hpp>
+#include <tsl/robin_set.h>
+
+#include "dynarmic/backend/riscv64/stack_layout.h"
+#include "dynarmic/ir/cond.h"
+#include "dynarmic/ir/microinstruction.h"
+#include "dynarmic/ir/value.h"
+
+namespace Dynarmic::Backend::RV64 {
+
+class RegAlloc;
+
+struct HostLoc {
+    enum class Kind {
+        Gpr,
+        Fpr,
+        Spill,
+    } kind;
+    u32 index;
+};
+
+struct Argument {
+public:
+    using copyable_reference = std::reference_wrapper<Argument>;
+
+    IR::Type GetType() const;
+    bool IsImmediate() const;
+
+    bool GetImmediateU1() const;
+    u8 GetImmediateU8() const;
+    u16 GetImmediateU16() const;
+    u32 GetImmediateU32() const;
+    u64 GetImmediateU64() const;
+    IR::Cond GetImmediateCond() const;
+    IR::AccType GetImmediateAccType() const;
+
+private:
+    friend class RegAlloc;
+    explicit Argument(RegAlloc& reg_alloc)
+            : reg_alloc{reg_alloc} {}
+
+    bool allocated = false;
+    RegAlloc& reg_alloc;
+    IR::Value value;
+};
+
+template<typename T>
+struct RAReg {
+public:
+    static constexpr bool is_fpr = std::is_base_of_v<biscuit::FPR, T>;
+
+    operator T() const { return *reg; }
+
+    T operator*() const { return *reg; }
+
+    ~RAReg();
+
+private:
+    friend class RegAlloc;
+    explicit RAReg(RegAlloc& reg_alloc, bool write, const IR::Inst* value)
+            : reg_alloc{reg_alloc}, write{write}, value{value} {}
+
+    void Realize();
+
+    RegAlloc& reg_alloc;
+    bool write;
+    const IR::Inst* value;
+    std::optional<T> reg;
+};
+
+struct HostLocInfo final {
+    std::vector<const IR::Inst*> values;
+    bool locked = false;
+    bool realized = false;
+    size_t accumulated_uses = 0;
+    size_t expected_uses = 0;
+
+    bool Contains(const IR::Inst*) const;
+};
+
+class RegAlloc {
+public:
+    using ArgumentInfo = std::array<Argument, IR::max_arg_count>;
+
+    explicit RegAlloc(biscuit::Assembler& as, std::vector<u32> gpr_order, std::vector<u32> fpr_order)
+            : as{as}, gpr_order{gpr_order}, fpr_order{fpr_order}, rand_gen{std::random_device{}()} {}
+
+    ArgumentInfo GetArgumentInfo(IR::Inst* inst);
+    bool IsValueLive(IR::Inst* inst) const;
+
+    auto ReadX(Argument& arg) { return RAReg<biscuit::GPR>{*this, false, PreReadImpl(arg.value)}; }
+    auto ReadD(Argument& arg) { return RAReg<biscuit::FPR>{*this, false, PreReadImpl(arg.value)}; }
+
+    auto WriteX(IR::Inst* inst) { return RAReg<biscuit::GPR>{*this, true, inst}; }
+    auto WriteD(IR::Inst* inst) { return RAReg<biscuit::FPR>{*this, true, inst}; }
+
+    void SpillAll();
+
+    template<typename... Ts>
+    static void Realize(Ts&... rs) {
+        static_assert((mcl::is_instance_of_template<RAReg, Ts>() && ...));
+        (rs.Realize(), ...);
+    }
+
+private:
+    template<typename>
+    friend struct RAReg;
+
+    const IR::Inst* PreReadImpl(const IR::Value& value) {
+        ValueInfo(value.GetInst()).locked = true;
+        return value.GetInst();
+    }
+
+    template<bool is_fpr>
+    u32 RealizeReadImpl(const IR::Inst* value);
+    template<bool is_fpr>
+    u32 RealizeWriteImpl(const IR::Inst* value);
+    void Unlock(HostLoc host_loc);
+
+    u32 AllocateRegister(const std::array<HostLocInfo, 32>& regs, const std::vector<u32>& order) const;
+    void SpillGpr(u32 index);
+    void SpillFpr(u32 index);
+    u32 FindFreeSpill() const;
+
+    std::optional<HostLoc> ValueLocation(const IR::Inst* value) const;
+    HostLocInfo& ValueInfo(HostLoc host_loc);
+    HostLocInfo& ValueInfo(const IR::Inst* value);
+
+    biscuit::Assembler& as;
+    std::vector<u32> gpr_order;
+    std::vector<u32> fpr_order;
+
+    std::array<HostLocInfo, 32> gprs;
+    std::array<HostLocInfo, 32> fprs;
+    std::array<HostLocInfo, SpillCount> spills;
+
+    mutable std::mt19937 rand_gen;
+};
+
+template<typename T>
+RAReg<T>::~RAReg() {
+    if (reg) {
+        reg_alloc.Unlock(HostLoc{is_fpr ? HostLoc::Kind::Fpr : HostLoc::Kind::Gpr, reg->Index()});
+    }
+}
+
+template<typename T>
+void RAReg<T>::Realize() {
+    reg = T{write ? reg_alloc.RealizeWriteImpl<is_fpr>(value) : reg_alloc.RealizeReadImpl<is_fpr>(value)};
+}
+
+}  // namespace Dynarmic::Backend::RV64

src/dynarmic/backend/riscv64/stack_layout.h

@@ -0,0 +1,30 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2024 MerryMage
+ * SPDX-License-Identifier: 0BSD
+ */
+
+#pragma once
+
+#include <array>
+
+#include <mcl/stdint.hpp>
+
+namespace Dynarmic::Backend::RV64 {
+
+constexpr size_t SpillCount = 64;
+
+struct alignas(16) StackLayout {
+    s64 cycles_remaining;
+    s64 cycles_to_run;
+
+    std::array<u64, SpillCount> spill;
+
+    u32 save_host_fpcr;
+    u32 save_host_fpsr;
+
+    bool check_bit;
+};
+
+static_assert(sizeof(StackLayout) % 16 == 0);
+
+}  // namespace Dynarmic::Backend::RV64