[GlobalISel] Match LLVM legalization value tracking

1 files changed, 53 insertions, 0 deletions

diff --git a/backend/include/rcc/CodeGen/GlobalISel/GISelValueTracking.h b/backend/include/rcc/CodeGen/GlobalISel/GISelValueTracking.h
new file mode 100644
index 0000000..aa02fe3
--- /dev/null
+++ b/backend/include/rcc/CodeGen/GlobalISel/GISelValueTracking.h
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_CODEGEN_GLOBALISEL_GISELVALUETRACKING_H
+#define RCC_CODEGEN_GLOBALISEL_GISELVALUETRACKING_H
+
+#include "rcc/ADT/APInt.h"
+#include "rcc/CodeGen/GlobalISel/GISelChangeObserver.h"
+#include "rcc/CodeGen/Register.h"
+#include "rcc/Support/Error.h"
+
+#include <cstdint>
+
+namespace rcc {
+
+class MachineFunction;
+class MachineRegisterInfo;
+class TargetDescription;
+
+class GISelValueTracking final : public GISelChangeObserver {
+public:
+  GISelValueTracking(MachineFunction &Function, const TargetDescription &Target,
+                     unsigned MaxDepth = 6) noexcept;
+
+  [[nodiscard]] const MachineFunction &getMachineFunction() const noexcept {
+    return Function;
+  }
+
+  [[nodiscard]] Expected<APInt> getKnownZeroes(Register Reg) const;
+  [[nodiscard]] Expected<std::uint32_t> computeNumSignBits(Register Reg, unsigned Depth = 0) const;
+
+  void erasingInstr(MachineInstr &) override {}
+  void createdInstr(MachineInstr &) override {}
+  void changingInstr(MachineInstr &) override {}
+  void changedInstr(MachineInstr &) override {}
+
+private:
+  struct KnownBits final {
+    APInt Zero;
+    APInt One;
+  };
+
+  [[nodiscard]] Expected<KnownBits> makeUnknown(std::uint32_t BitWidth) const;
+  [[nodiscard]] Expected<KnownBits> getKnownBits(Register Reg, unsigned Depth = 0) const;
+
+  MachineFunction &Function;
+  MachineRegisterInfo &MRI;
+  const TargetDescription &Target;
+  unsigned MaxDepth;
+};
+
+} // namespace rcc
+
+#endif // RCC_CODEGEN_GLOBALISEL_GISELVALUETRACKING_H