From 10b7e69448f866bcd6893b21d7f78d766252eb11 Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Sat, 8 Aug 2026 02:58:50 +0800
Subject: [CodeGen] Implement RV64GC legalization and instruction selection

---
 backend/include/rcc/CodeGen/TargetCodeGen.h | 94 +++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 backend/include/rcc/CodeGen/TargetCodeGen.h

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

diff --git a/backend/include/rcc/CodeGen/TargetCodeGen.h b/backend/include/rcc/CodeGen/TargetCodeGen.h
new file mode 100644
index 0000000..b1be1f6
--- /dev/null
+++ b/backend/include/rcc/CodeGen/TargetCodeGen.h
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_CODEGEN_TARGETCODEGEN_H
+#define RCC_CODEGEN_TARGETCODEGEN_H
+
+#include "rcc/CodeGen/MachineIRTypes.h"
+#include "rcc/CodeGen/Register.h"
+#include "rcc/Support/Error.h"
+
+#include <cstdint>
+#include <optional>
+
+namespace rcc {
+
+class MachineFunction;
+class MachineInstr;
+class MachineRegisterInfo;
+class TargetDescription;
+struct VirtualRegisterInfo;
+
+enum class LegalizationAction : std::uint8_t {
+  Legal,
+  Unsupported,
+  Custom,
+  Lower,
+  Libcall,
+  WidenScalar,
+  NarrowScalar,
+  MoreElements,
+  FewerElements,
+  Bitcast,
+  ChangeElementType,
+  ChangeAddressSpace,
+};
+
+class TargetLegalizerInfo {
+public:
+  virtual ~TargetLegalizerInfo() = default;
+
+  [[nodiscard]] virtual Expected<LegalizationAction>
+  classify(const MachineInstr &Instruction, const MachineFunction &Function,
+           const TargetDescription &Target) const = 0;
+
+  [[nodiscard]] virtual Expected<void> lower(MachineInstr &Instruction, MachineFunction &Function,
+                                             const TargetDescription &Target,
+                                             LegalizationAction Action) const = 0;
+
+  // This hook performs read-only target checks before a lowering mutation is committed.
+  [[nodiscard]] virtual Expected<void> validateLowering(const MachineInstr &,
+                                                        const MachineFunction &,
+                                                        const TargetDescription &,
+                                                        LegalizationAction) const {
+    return {};
+  }
+};
+
+class TargetRegisterBankInfo {
+public:
+  virtual ~TargetRegisterBankInfo() = default;
+
+  [[nodiscard]] virtual Expected<RegisterBankID>
+  selectBank(const MachineFunction &Function, Register Reg, const VirtualRegisterInfo &Info,
+             const MachineInstr *Context, const TargetDescription &Target) const = 0;
+
+  [[nodiscard]] virtual Expected<void>
+  constrainInstruction(MachineInstr &Instruction, MachineFunction &Function,
+                       const TargetDescription &Target) const = 0;
+
+  // This hook must not mutate MachineIR. It allows the pass to reject a bad mapping
+  // before publishing any bank or class assignment.
+  [[nodiscard]] virtual Expected<void> validateInstruction(const MachineInstr &,
+                                                           const MachineFunction &,
+                                                           const TargetDescription &) const {
+    return {};
+  }
+};
+
+class TargetInstructionSelector {
+public:
+  virtual ~TargetInstructionSelector() = default;
+
+  [[nodiscard]] virtual Expected<void> select(MachineInstr &Instruction, MachineFunction &Function,
+                                              const TargetDescription &Target) const = 0;
+
+  // Selection matching is read-only and must complete before select() mutates MachineIR.
+  [[nodiscard]] virtual Expected<void> canSelect(const MachineInstr &, const MachineFunction &,
+                                                 const TargetDescription &) const {
+    return {};
+  }
+};
+
+} // namespace rcc
+
+#endif // RCC_CODEGEN_TARGETCODEGEN_H
-- 
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