3 files changed, 173 insertions, 0 deletions
diff --git a/backend/include/rcc/CodeGen/MachinePipelinePasses.h b/backend/include/rcc/CodeGen/MachinePipelinePasses.h
new file mode 100644
index 0000000..c5bdac0
--- /dev/null
+++ b/backend/include/rcc/CodeGen/MachinePipelinePasses.h
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_CODEGEN_MACHINEPIPELINEPASSES_H
+#define RCC_CODEGEN_MACHINEPIPELINEPASSES_H
+
+#include "rcc/CodeGen/MachinePass.h"
+#include "rcc/CodeGen/TargetCodeGen.h"
+
+namespace rcc {
+
+class LegalizerPass final : public MachineFunctionPass {
+public:
+  explicit LegalizerPass(const TargetLegalizerInfo *Info) : Info(Info) {}
+  explicit LegalizerPass(const TargetLegalizerInfo &Info) : Info(&Info) {}
+
+  [[nodiscard]] const MachinePassContract &contract() const noexcept override;
+  [[nodiscard]] Expected<MachinePassResult> run(MachineFunction &Function,
+                                                const TargetDescription &Target,
+                                                MachineAnalysisManager &Analyses) override;
+
+private:
+  [[nodiscard]] Expected<MachinePassResult> runImplementation(MachineFunction &Function,
+                                                              const TargetDescription &Target,
+                                                              MachineAnalysisManager &Analyses);
+
+  const TargetLegalizerInfo *Info;
+};
+
+class RegisterBankSelectPass final : public MachineFunctionPass {
+public:
+  explicit RegisterBankSelectPass(const TargetRegisterBankInfo *Info) : Info(Info) {}
+  explicit RegisterBankSelectPass(const TargetRegisterBankInfo &Info) : Info(&Info) {}
+
+  [[nodiscard]] const MachinePassContract &contract() const noexcept override;
+  [[nodiscard]] Expected<MachinePassResult> run(MachineFunction &Function,
+                                                const TargetDescription &Target,
+                                                MachineAnalysisManager &Analyses) override;
+
+private:
+  const TargetRegisterBankInfo *Info;
+};
+
+class InstructionSelectPass final : public MachineFunctionPass {
+public:
+  explicit InstructionSelectPass(const TargetInstructionSelector *Info) : Info(Info) {}
+  explicit InstructionSelectPass(const TargetInstructionSelector &Info) : Info(&Info) {}
+
+  [[nodiscard]] const MachinePassContract &contract() const noexcept override;
+  [[nodiscard]] Expected<MachinePassResult> run(MachineFunction &Function,
+                                                const TargetDescription &Target,
+                                                MachineAnalysisManager &Analyses) override;
+
+private:
+  [[nodiscard]] Expected<MachinePassResult> runImplementation(MachineFunction &Function,
+                                                              const TargetDescription &Target,
+                                                              MachineAnalysisManager &Analyses);
+
+  const TargetInstructionSelector *Info;
+};
+
+} // namespace rcc
+
+#endif // RCC_CODEGEN_MACHINEPIPELINEPASSES_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
diff --git a/backend/include/rcc/Target/RISCV/RISCVCodeGen.h b/backend/include/rcc/Target/RISCV/RISCVCodeGen.h
new file mode 100644
index 0000000..b06f20d
--- /dev/null
+++ b/backend/include/rcc/Target/RISCV/RISCVCodeGen.h
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_TARGET_RISCV_RISCVCODEGEN_H
+#define RCC_TARGET_RISCV_RISCVCODEGEN_H
+
+#include "rcc/CodeGen/TargetCodeGen.h"
+
+namespace rcc::riscv {
+
+[[nodiscard]] const TargetLegalizerInfo &legalizerInfo() noexcept;
+[[nodiscard]] const TargetRegisterBankInfo &registerBankInfo() noexcept;
+[[nodiscard]] const TargetInstructionSelector &instructionSelector() noexcept;
+
+} // namespace rcc::riscv
+
+#endif // RCC_TARGET_RISCV_RISCVCODEGEN_H