From 495c675771f43cfa12ab7a426a538be72fec1805 Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Sun, 9 Aug 2026 17:03:19 +0800
Subject: [CodeGen] Implement machine optimization and scheduling

---
 backend/include/rcc/CodeGen/ScheduleDAG.h | 110 ++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 backend/include/rcc/CodeGen/ScheduleDAG.h

(limited to 'backend/include/rcc/CodeGen/ScheduleDAG.h')

diff --git a/backend/include/rcc/CodeGen/ScheduleDAG.h b/backend/include/rcc/CodeGen/ScheduleDAG.h
new file mode 100644
index 0000000..644d98a
--- /dev/null
+++ b/backend/include/rcc/CodeGen/ScheduleDAG.h
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_CODEGEN_SCHEDULEDAG_H
+#define RCC_CODEGEN_SCHEDULEDAG_H
+
+#include "rcc/CodeGen/StableID.h"
+#include "rcc/CodeGen/TargetSchedulingModel.h"
+#include "rcc/Support/Error.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <span>
+#include <vector>
+
+namespace rcc {
+
+class MachineBasicBlock;
+class MachineFunction;
+class MachineInstr;
+class TargetDescription;
+
+enum class ScheduleDAGMode : std::uint8_t {
+  PreRegisterAllocation,
+  PostRegisterAllocation,
+};
+
+enum class ScheduleDependencyKind : std::uint8_t {
+  Data,
+  Anti,
+  Output,
+  Order,
+  Memory,
+  Barrier,
+  Artificial,
+  RegisterUnit,
+  RegisterMask,
+};
+
+struct ScheduleDependency final {
+  std::size_t Source = 0;
+  std::size_t Destination = 0;
+  ScheduleDependencyKind Kind = ScheduleDependencyKind::Artificial;
+  std::uint32_t Latency = 0;
+
+  friend constexpr bool operator==(const ScheduleDependency &,
+                                   const ScheduleDependency &) noexcept = default;
+};
+
+struct ScheduleUnit final {
+  std::size_t ID = 0;
+  std::vector<MachineInstr *> Instructions;
+  std::vector<ScheduleDependency> Predecessors;
+  std::vector<ScheduleDependency> Successors;
+  std::vector<SchedulingResourceUse> Resources;
+  std::uint32_t MicroOps = 0;
+  std::uint32_t Latency = 0;
+  std::uint64_t Depth = 0;
+  std::uint64_t Height = 0;
+  MachineInstrStableID StableID;
+};
+
+class ScheduleDAG final {
+public:
+  [[nodiscard]] static Expected<ScheduleDAG>
+  build(MachineBasicBlock &Block, std::span<MachineInstr *const> Instructions,
+        const MachineFunction &Function, const TargetDescription &Target,
+        const TargetSchedulingModel &Model, ScheduleDAGMode Mode);
+
+  [[nodiscard]] MachineBasicBlock &block() const noexcept {
+    return *Block;
+  }
+
+  [[nodiscard]] std::span<const ScheduleUnit> units() const noexcept {
+    return Units;
+  }
+
+  [[nodiscard]] std::span<ScheduleUnit> units() noexcept {
+    return Units;
+  }
+
+  [[nodiscard]] const ScheduleUnit *unit(std::size_t ID) const noexcept {
+    return ID < Units.size() ? &Units[ID] : nullptr;
+  }
+
+  [[nodiscard]] Expected<void> addArtificialDependency(std::size_t Source, std::size_t Destination,
+                                                       std::uint32_t Latency);
+
+private:
+  explicit ScheduleDAG(MachineBasicBlock &Block) : Block(&Block) {}
+
+  [[nodiscard]] Expected<void> buildUnits(std::span<MachineInstr *const> Instructions,
+                                          const TargetDescription &Target,
+                                          const TargetSchedulingModel &Model);
+  [[nodiscard]] Expected<void> buildRegisterDependencies(const MachineFunction &Function,
+                                                         const TargetDescription &Target,
+                                                         const TargetSchedulingModel &Model,
+                                                         ScheduleDAGMode Mode);
+  [[nodiscard]] Expected<void> buildMemoryDependencies(const TargetDescription &Target);
+  [[nodiscard]] Expected<void> buildOrderDependencies(const TargetDescription &Target);
+  void addDependency(std::size_t Source, std::size_t Destination, ScheduleDependencyKind Kind,
+                     std::uint32_t Latency);
+  void computeCriticalPaths();
+
+  MachineBasicBlock *Block;
+  std::vector<ScheduleUnit> Units;
+};
+
+} // namespace rcc
+
+#endif // RCC_CODEGEN_SCHEDULEDAG_H
-- 
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