Imported Upstream version 6.0.0.172

Former-commit-id: f3cc9b82f3e5bd8f0fd3ebc098f789556b44e9cd

external/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.h

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+// WebAssemblyFrameLowering.h - TargetFrameLowering for WebAssembly -*- C++ -*-/
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This class implements WebAssembly-specific bits of
+/// TargetFrameLowering class.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYFRAMELOWERING_H
+#define LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYFRAMELOWERING_H
+
+#include "llvm/CodeGen/TargetFrameLowering.h"
+
+namespace llvm {
+class MachineFrameInfo;
+
+class WebAssemblyFrameLowering final : public TargetFrameLowering {
+ public:
+  /// Size of the red zone for the user stack (leaf functions can use this much
+  /// space below the stack pointer without writing it back to memory).
+  // TODO: (ABI) Revisit and decide how large it should be.
+  static const size_t RedZoneSize = 128;
+
+  WebAssemblyFrameLowering()
+      : TargetFrameLowering(StackGrowsDown, /*StackAlignment=*/16,
+                            /*LocalAreaOffset=*/0,
+                            /*TransientStackAlignment=*/16,
+                            /*StackRealignable=*/true) {}
+
+  MachineBasicBlock::iterator eliminateCallFramePseudoInstr(
+      MachineFunction &MF, MachineBasicBlock &MBB,
+      MachineBasicBlock::iterator I) const override;
+
+  /// These methods insert prolog and epilog code into the function.
+  void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
+  void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
+
+  bool hasFP(const MachineFunction &MF) const override;
+  bool hasReservedCallFrame(const MachineFunction &MF) const override;
+
+ private:
+  bool hasBP(const MachineFunction &MF) const;
+  bool needsSP(const MachineFunction &MF, const MachineFrameInfo &MFI) const;
+  bool needsSPWriteback(const MachineFunction &MF,
+                        const MachineFrameInfo &MFI) const;
+};
+
+}  // end namespace llvm
+
+#endif