From 8a4bb6e3b0bffa0ed79b51347b12ee4293b622a7 Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Sat, 22 Aug 2026 18:49:08 +0800
Subject: [CodeGen] Generate RISC-V macro fusion rules

---
 backend/include/rcc/CodeGen/MacroFusion.h | 77 +++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 backend/include/rcc/CodeGen/MacroFusion.h

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

diff --git a/backend/include/rcc/CodeGen/MacroFusion.h b/backend/include/rcc/CodeGen/MacroFusion.h
new file mode 100644
index 0000000..c3d811d
--- /dev/null
+++ b/backend/include/rcc/CodeGen/MacroFusion.h
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_CODEGEN_MACROFUSION_H
+#define RCC_CODEGEN_MACROFUSION_H
+
+#include "rcc/CodeGen/MachineIRTypes.h"
+#include "rcc/Support/Error.h"
+
+#include <cstdint>
+#include <limits>
+#include <span>
+#include <string_view>
+
+namespace rcc {
+
+class MachineInstr;
+class ScheduleDAG;
+class TargetDescription;
+
+enum class MacroFusionInstruction : std::uint8_t {
+  First,
+  Second,
+};
+
+struct MacroFusionOpcodePair final {
+  Opcode First;
+  Opcode Second;
+};
+
+struct MacroFusionImmediatePredicate final {
+  MacroFusionInstruction Instruction = MacroFusionInstruction::First;
+  std::uint32_t OperandIndex = 0;
+  std::int64_t Minimum = 0;
+  std::int64_t Maximum = 0;
+};
+
+struct MacroFusionRegisterInequality final {
+  MacroFusionInstruction Instruction = MacroFusionInstruction::First;
+  std::uint32_t LeftOperand = 0;
+  std::uint32_t RightOperand = 0;
+};
+
+struct MacroFusionImmediateRelation final {
+  std::uint32_t FirstOperand = 0;
+  std::uint32_t SecondOperand = 0;
+};
+
+struct MacroFusionRule final {
+  static constexpr std::uint32_t NoOperand = std::numeric_limits<std::uint32_t>::max();
+
+  std::string_view Name;
+  std::string_view Feature;
+  std::span<const Opcode> FirstOpcodes;
+  std::span<const Opcode> SecondOpcodes;
+  std::span<const MacroFusionOpcodePair> OpcodePairs;
+  std::span<const MacroFusionImmediatePredicate> ImmediatePredicates;
+  std::span<const MacroFusionRegisterInequality> RegisterInequalities;
+  std::span<const MacroFusionImmediateRelation> ImmediateRelations;
+  std::uint32_t FirstDefinitionOperand = 0;
+  std::uint32_t SecondUseOperand = 1;
+  std::uint32_t SecondDefinitionOperand = 0;
+  std::uint32_t CommutableSecondUseOperand = NoOperand;
+  bool RequireSingleNonDebugUse = false;
+  bool RequireSecondDestinationTie = false;
+};
+
+[[nodiscard]] bool matchesMacroFusion(const MacroFusionRule &Rule, const MachineInstr *First,
+                                      const MachineInstr &Second) noexcept;
+
+[[nodiscard]] Expected<void> applyMacroFusion(ScheduleDAG &DAG,
+                                              std::span<const MacroFusionRule> Rules,
+                                              const TargetDescription &Target,
+                                              bool EmitDebugOutput);
+
+} // namespace rcc
+
+#endif // RCC_CODEGEN_MACROFUSION_H
-- 
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