vendor/llvm/llvm-trunk-r321017

1 files changed, 348 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/TargetFrameLowering.h b/include/llvm/CodeGen/TargetFrameLowering.h
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+++ b/include/llvm/CodeGen/TargetFrameLowering.h
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+//===-- llvm/CodeGen/TargetFrameLowering.h ----------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Interface to describe the layout of a stack frame on the target machine.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_TARGETFRAMELOWERING_H
+#define LLVM_CODEGEN_TARGETFRAMELOWERING_H
+
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include <utility>
+#include <vector>
+
+namespace llvm {
+  class BitVector;
+  class CalleeSavedInfo;
+  class MachineFunction;
+  class RegScavenger;
+
+/// Information about stack frame layout on the target.  It holds the direction
+/// of stack growth, the known stack alignment on entry to each function, and
+/// the offset to the locals area.
+///
+/// The offset to the local area is the offset from the stack pointer on
+/// function entry to the first location where function data (local variables,
+/// spill locations) can be stored.
+class TargetFrameLowering {
+public:
+  enum StackDirection {
+    StackGrowsUp,        // Adding to the stack increases the stack address
+    StackGrowsDown       // Adding to the stack decreases the stack address
+  };
+
+  // Maps a callee saved register to a stack slot with a fixed offset.
+  struct SpillSlot {
+    unsigned Reg;
+    int Offset; // Offset relative to stack pointer on function entry.
+  };
+private:
+  StackDirection StackDir;
+  unsigned StackAlignment;
+  unsigned TransientStackAlignment;
+  int LocalAreaOffset;
+  bool StackRealignable;
+public:
+  TargetFrameLowering(StackDirection D, unsigned StackAl, int LAO,
+                      unsigned TransAl = 1, bool StackReal = true)
+    : StackDir(D), StackAlignment(StackAl), TransientStackAlignment(TransAl),
+      LocalAreaOffset(LAO), StackRealignable(StackReal) {}
+
+  virtual ~TargetFrameLowering();
+
+  // These methods return information that describes the abstract stack layout
+  // of the target machine.
+
+  /// getStackGrowthDirection - Return the direction the stack grows
+  ///
+  StackDirection getStackGrowthDirection() const { return StackDir; }
+
+  /// getStackAlignment - This method returns the number of bytes to which the
+  /// stack pointer must be aligned on entry to a function.  Typically, this
+  /// is the largest alignment for any data object in the target.
+  ///
+  unsigned getStackAlignment() const { return StackAlignment; }
+
+  /// alignSPAdjust - This method aligns the stack adjustment to the correct
+  /// alignment.
+  ///
+  int alignSPAdjust(int SPAdj) const {
+    if (SPAdj < 0) {
+      SPAdj = -alignTo(-SPAdj, StackAlignment);
+    } else {
+      SPAdj = alignTo(SPAdj, StackAlignment);
+    }
+    return SPAdj;
+  }
+
+  /// getTransientStackAlignment - This method returns the number of bytes to
+  /// which the stack pointer must be aligned at all times, even between
+  /// calls.
+  ///
+  unsigned getTransientStackAlignment() const {
+    return TransientStackAlignment;
+  }
+
+  /// isStackRealignable - This method returns whether the stack can be
+  /// realigned.
+  bool isStackRealignable() const {
+    return StackRealignable;
+  }
+
+  /// Return the skew that has to be applied to stack alignment under
+  /// certain conditions (e.g. stack was adjusted before function \p MF
+  /// was called).
+  virtual unsigned getStackAlignmentSkew(const MachineFunction &MF) const;
+
+  /// getOffsetOfLocalArea - This method returns the offset of the local area
+  /// from the stack pointer on entrance to a function.
+  ///
+  int getOffsetOfLocalArea() const { return LocalAreaOffset; }
+
+  /// isFPCloseToIncomingSP - Return true if the frame pointer is close to
+  /// the incoming stack pointer, false if it is close to the post-prologue
+  /// stack pointer.
+  virtual bool isFPCloseToIncomingSP() const { return true; }
+
+  /// assignCalleeSavedSpillSlots - Allows target to override spill slot
+  /// assignment logic.  If implemented, assignCalleeSavedSpillSlots() should
+  /// assign frame slots to all CSI entries and return true.  If this method
+  /// returns false, spill slots will be assigned using generic implementation.
+  /// assignCalleeSavedSpillSlots() may add, delete or rearrange elements of
+  /// CSI.
+  virtual bool
+  assignCalleeSavedSpillSlots(MachineFunction &MF,
+                              const TargetRegisterInfo *TRI,
+                              std::vector<CalleeSavedInfo> &CSI) const {
+    return false;
+  }
+
+  /// getCalleeSavedSpillSlots - This method returns a pointer to an array of
+  /// pairs, that contains an entry for each callee saved register that must be
+  /// spilled to a particular stack location if it is spilled.
+  ///
+  /// Each entry in this array contains a <register,offset> pair, indicating the
+  /// fixed offset from the incoming stack pointer that each register should be
+  /// spilled at. If a register is not listed here, the code generator is
+  /// allowed to spill it anywhere it chooses.
+  ///
+  virtual const SpillSlot *
+  getCalleeSavedSpillSlots(unsigned &NumEntries) const {
+    NumEntries = 0;
+    return nullptr;
+  }
+
+  /// targetHandlesStackFrameRounding - Returns true if the target is
+  /// responsible for rounding up the stack frame (probably at emitPrologue
+  /// time).
+  virtual bool targetHandlesStackFrameRounding() const {
+    return false;
+  }
+
+  /// Returns true if the target will correctly handle shrink wrapping.
+  virtual bool enableShrinkWrapping(const MachineFunction &MF) const {
+    return false;
+  }
+
+  /// Returns true if the stack slot holes in the fixed and callee-save stack
+  /// area should be used when allocating other stack locations to reduce stack
+  /// size.
+  virtual bool enableStackSlotScavenging(const MachineFunction &MF) const {
+    return false;
+  }
+
+  /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
+  /// the function.
+  virtual void emitPrologue(MachineFunction &MF,
+                            MachineBasicBlock &MBB) const = 0;
+  virtual void emitEpilogue(MachineFunction &MF,
+                            MachineBasicBlock &MBB) const = 0;
+
+  /// Replace a StackProbe stub (if any) with the actual probe code inline
+  virtual void inlineStackProbe(MachineFunction &MF,
+                                MachineBasicBlock &PrologueMBB) const {}
+
+  /// Adjust the prologue to have the function use segmented stacks. This works
+  /// by adding a check even before the "normal" function prologue.
+  virtual void adjustForSegmentedStacks(MachineFunction &MF,
+                                        MachineBasicBlock &PrologueMBB) const {}
+
+  /// Adjust the prologue to add Erlang Run-Time System (ERTS) specific code in
+  /// the assembly prologue to explicitly handle the stack.
+  virtual void adjustForHiPEPrologue(MachineFunction &MF,
+                                     MachineBasicBlock &PrologueMBB) const {}
+
+  /// spillCalleeSavedRegisters - Issues instruction(s) to spill all callee
+  /// saved registers and returns true if it isn't possible / profitable to do
+  /// so by issuing a series of store instructions via
+  /// storeRegToStackSlot(). Returns false otherwise.
+  virtual bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
+                                         MachineBasicBlock::iterator MI,
+                                        const std::vector<CalleeSavedInfo> &CSI,
+                                         const TargetRegisterInfo *TRI) const {
+    return false;
+  }
+
+  /// restoreCalleeSavedRegisters - Issues instruction(s) to restore all callee
+  /// saved registers and returns true if it isn't possible / profitable to do
+  /// so by issuing a series of load instructions via loadRegToStackSlot().
+  /// If it returns true, and any of the registers in CSI is not restored,
+  /// it sets the corresponding Restored flag in CSI to false.
+  /// Returns false otherwise.
+  virtual bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
+                                           MachineBasicBlock::iterator MI,
+                                           std::vector<CalleeSavedInfo> &CSI,
+                                        const TargetRegisterInfo *TRI) const {
+    return false;
+  }
+
+  /// Return true if the target needs to disable frame pointer elimination.
+  virtual bool noFramePointerElim(const MachineFunction &MF) const;
+
+  /// hasFP - Return true if the specified function should have a dedicated
+  /// frame pointer register. For most targets this is true only if the function
+  /// has variable sized allocas or if frame pointer elimination is disabled.
+  virtual bool hasFP(const MachineFunction &MF) const = 0;
+
+  /// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
+  /// not required, we reserve argument space for call sites in the function
+  /// immediately on entry to the current function. This eliminates the need for
+  /// add/sub sp brackets around call sites. Returns true if the call frame is
+  /// included as part of the stack frame.
+  virtual bool hasReservedCallFrame(const MachineFunction &MF) const {
+    return !hasFP(MF);
+  }
+
+  /// canSimplifyCallFramePseudos - When possible, it's best to simplify the
+  /// call frame pseudo ops before doing frame index elimination. This is
+  /// possible only when frame index references between the pseudos won't
+  /// need adjusting for the call frame adjustments. Normally, that's true
+  /// if the function has a reserved call frame or a frame pointer. Some
+  /// targets (Thumb2, for example) may have more complicated criteria,
+  /// however, and can override this behavior.
+  virtual bool canSimplifyCallFramePseudos(const MachineFunction &MF) const {
+    return hasReservedCallFrame(MF) || hasFP(MF);
+  }
+
+  // needsFrameIndexResolution - Do we need to perform FI resolution for
+  // this function. Normally, this is required only when the function
+  // has any stack objects. However, targets may want to override this.
+  virtual bool needsFrameIndexResolution(const MachineFunction &MF) const;
+
+  /// getFrameIndexReference - This method should return the base register
+  /// and offset used to reference a frame index location. The offset is
+  /// returned directly, and the base register is returned via FrameReg.
+  virtual int getFrameIndexReference(const MachineFunction &MF, int FI,
+                                     unsigned &FrameReg) const;
+
+  /// Same as \c getFrameIndexReference, except that the stack pointer (as
+  /// opposed to the frame pointer) will be the preferred value for \p
+  /// FrameReg. This is generally used for emitting statepoint or EH tables that
+  /// use offsets from RSP.  If \p IgnoreSPUpdates is true, the returned
+  /// offset is only guaranteed to be valid with respect to the value of SP at
+  /// the end of the prologue.
+  virtual int getFrameIndexReferencePreferSP(const MachineFunction &MF, int FI,
+                                             unsigned &FrameReg,
+                                             bool IgnoreSPUpdates) const {
+    // Always safe to dispatch to getFrameIndexReference.
+    return getFrameIndexReference(MF, FI, FrameReg);
+  }
+
+  /// This method determines which of the registers reported by
+  /// TargetRegisterInfo::getCalleeSavedRegs() should actually get saved.
+  /// The default implementation checks populates the \p SavedRegs bitset with
+  /// all registers which are modified in the function, targets may override
+  /// this function to save additional registers.
+  /// This method also sets up the register scavenger ensuring there is a free
+  /// register or a frameindex available.
+  virtual void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
+                                    RegScavenger *RS = nullptr) const;
+
+  /// processFunctionBeforeFrameFinalized - This method is called immediately
+  /// before the specified function's frame layout (MF.getFrameInfo()) is
+  /// finalized.  Once the frame is finalized, MO_FrameIndex operands are
+  /// replaced with direct constants.  This method is optional.
+  ///
+  virtual void processFunctionBeforeFrameFinalized(MachineFunction &MF,
+                                             RegScavenger *RS = nullptr) const {
+  }
+
+  virtual unsigned getWinEHParentFrameOffset(const MachineFunction &MF) const {
+    report_fatal_error("WinEH not implemented for this target");
+  }
+
+  /// This method is called during prolog/epilog code insertion to eliminate
+  /// call frame setup and destroy pseudo instructions (but only if the Target
+  /// is using them).  It is responsible for eliminating these instructions,
+  /// replacing them with concrete instructions.  This method need only be
+  /// implemented if using call frame setup/destroy pseudo instructions.
+  /// Returns an iterator pointing to the instruction after the replaced one.
+  virtual MachineBasicBlock::iterator
+  eliminateCallFramePseudoInstr(MachineFunction &MF,
+                                MachineBasicBlock &MBB,
+                                MachineBasicBlock::iterator MI) const {
+    llvm_unreachable("Call Frame Pseudo Instructions do not exist on this "
+                     "target!");
+  }
+
+
+  /// Order the symbols in the local stack frame.
+  /// The list of objects that we want to order is in \p objectsToAllocate as
+  /// indices into the MachineFrameInfo. The array can be reordered in any way
+  /// upon return. The contents of the array, however, may not be modified (i.e.
+  /// only their order may be changed).
+  /// By default, just maintain the original order.
+  virtual void
+  orderFrameObjects(const MachineFunction &MF,
+                    SmallVectorImpl<int> &objectsToAllocate) const {
+  }
+
+  /// Check whether or not the given \p MBB can be used as a prologue
+  /// for the target.
+  /// The prologue will be inserted first in this basic block.
+  /// This method is used by the shrink-wrapping pass to decide if
+  /// \p MBB will be correctly handled by the target.
+  /// As soon as the target enable shrink-wrapping without overriding
+  /// this method, we assume that each basic block is a valid
+  /// prologue.
+  virtual bool canUseAsPrologue(const MachineBasicBlock &MBB) const {
+    return true;
+  }
+
+  /// Check whether or not the given \p MBB can be used as a epilogue
+  /// for the target.
+  /// The epilogue will be inserted before the first terminator of that block.
+  /// This method is used by the shrink-wrapping pass to decide if
+  /// \p MBB will be correctly handled by the target.
+  /// As soon as the target enable shrink-wrapping without overriding
+  /// this method, we assume that each basic block is a valid
+  /// epilogue.
+  virtual bool canUseAsEpilogue(const MachineBasicBlock &MBB) const {
+    return true;
+  }
+
+  /// Check if given function is safe for not having callee saved registers.
+  /// This is used when interprocedural register allocation is enabled.
+  static bool isSafeForNoCSROpt(const Function &F) {
+    if (!F.hasLocalLinkage() || F.hasAddressTaken() ||
+        !F.hasFnAttribute(Attribute::NoRecurse))
+      return false;
+    // Function should not be optimized as tail call.
+    for (const User *U : F.users())
+      if (auto CS = ImmutableCallSite(U))
+        if (CS.isTailCall())
+          return false;
+    return true;
+  }
+};
+
+} // End llvm namespace
+
+#endif