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This changes TargetFrameLowering::processFunctionBeforeCalleeSavedScan(): - Rename the function to determineCalleeSaves() - Pass a bitset of callee saved registers by reference, thus avoiding the function-global PhysRegUsed bitset in MachineRegisterInfo. - Without PhysRegUsed the implementation is fine tuned to not save physcial registers which are only read but never modified. Related to rdar://21539507 Differential Revision: http://reviews.llvm.org/D10909 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242165 91177308-0d34-0410-b5e6-96231b3b80d8
292 lines
13 KiB
C++
292 lines
13 KiB
C++
//===-- llvm/Target/TargetFrameLowering.h ---------------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Interface to describe the layout of a stack frame on the target machine.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TARGET_TARGETFRAMELOWERING_H
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#define LLVM_TARGET_TARGETFRAMELOWERING_H
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include <utility>
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#include <vector>
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namespace llvm {
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class BitVector;
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class CalleeSavedInfo;
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class MachineFunction;
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class RegScavenger;
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/// Information about stack frame layout on the target. It holds the direction
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/// of stack growth, the known stack alignment on entry to each function, and
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/// the offset to the locals area.
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///
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/// The offset to the local area is the offset from the stack pointer on
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/// function entry to the first location where function data (local variables,
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/// spill locations) can be stored.
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class TargetFrameLowering {
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public:
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enum StackDirection {
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StackGrowsUp, // Adding to the stack increases the stack address
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StackGrowsDown // Adding to the stack decreases the stack address
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};
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// Maps a callee saved register to a stack slot with a fixed offset.
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struct SpillSlot {
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unsigned Reg;
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int Offset; // Offset relative to stack pointer on function entry.
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};
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private:
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StackDirection StackDir;
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unsigned StackAlignment;
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unsigned TransientStackAlignment;
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int LocalAreaOffset;
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bool StackRealignable;
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public:
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TargetFrameLowering(StackDirection D, unsigned StackAl, int LAO,
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unsigned TransAl = 1, bool StackReal = true)
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: StackDir(D), StackAlignment(StackAl), TransientStackAlignment(TransAl),
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LocalAreaOffset(LAO), StackRealignable(StackReal) {}
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virtual ~TargetFrameLowering();
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// These methods return information that describes the abstract stack layout
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// of the target machine.
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/// getStackGrowthDirection - Return the direction the stack grows
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///
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StackDirection getStackGrowthDirection() const { return StackDir; }
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/// getStackAlignment - This method returns the number of bytes to which the
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/// stack pointer must be aligned on entry to a function. Typically, this
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/// is the largest alignment for any data object in the target.
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///
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unsigned getStackAlignment() const { return StackAlignment; }
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/// getTransientStackAlignment - This method returns the number of bytes to
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/// which the stack pointer must be aligned at all times, even between
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/// calls.
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///
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unsigned getTransientStackAlignment() const {
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return TransientStackAlignment;
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}
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/// isStackRealignable - This method returns whether the stack can be
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/// realigned.
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bool isStackRealignable() const {
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return StackRealignable;
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}
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/// getOffsetOfLocalArea - This method returns the offset of the local area
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/// from the stack pointer on entrance to a function.
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///
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int getOffsetOfLocalArea() const { return LocalAreaOffset; }
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/// isFPCloseToIncomingSP - Return true if the frame pointer is close to
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/// the incoming stack pointer, false if it is close to the post-prologue
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/// stack pointer.
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virtual bool isFPCloseToIncomingSP() const { return true; }
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/// assignCalleeSavedSpillSlots - Allows target to override spill slot
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/// assignment logic. If implemented, assignCalleeSavedSpillSlots() should
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/// assign frame slots to all CSI entries and return true. If this method
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/// returns false, spill slots will be assigned using generic implementation.
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/// assignCalleeSavedSpillSlots() may add, delete or rearrange elements of
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/// CSI.
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virtual bool
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assignCalleeSavedSpillSlots(MachineFunction &MF,
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const TargetRegisterInfo *TRI,
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std::vector<CalleeSavedInfo> &CSI) const {
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return false;
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}
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/// getCalleeSavedSpillSlots - This method returns a pointer to an array of
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/// pairs, that contains an entry for each callee saved register that must be
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/// spilled to a particular stack location if it is spilled.
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///
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/// Each entry in this array contains a <register,offset> pair, indicating the
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/// fixed offset from the incoming stack pointer that each register should be
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/// spilled at. If a register is not listed here, the code generator is
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/// allowed to spill it anywhere it chooses.
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///
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virtual const SpillSlot *
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getCalleeSavedSpillSlots(unsigned &NumEntries) const {
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NumEntries = 0;
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return nullptr;
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}
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/// targetHandlesStackFrameRounding - Returns true if the target is
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/// responsible for rounding up the stack frame (probably at emitPrologue
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/// time).
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virtual bool targetHandlesStackFrameRounding() const {
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return false;
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}
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/// emitProlog/emitEpilog - These methods insert prolog and epilog code into
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/// the function.
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virtual void emitPrologue(MachineFunction &MF,
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MachineBasicBlock &MBB) const = 0;
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virtual void emitEpilogue(MachineFunction &MF,
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MachineBasicBlock &MBB) const = 0;
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/// Adjust the prologue to have the function use segmented stacks. This works
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/// by adding a check even before the "normal" function prologue.
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virtual void adjustForSegmentedStacks(MachineFunction &MF,
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MachineBasicBlock &PrologueMBB) const {}
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/// Adjust the prologue to add Erlang Run-Time System (ERTS) specific code in
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/// the assembly prologue to explicitly handle the stack.
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virtual void adjustForHiPEPrologue(MachineFunction &MF,
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MachineBasicBlock &PrologueMBB) const {}
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/// Adjust the prologue to add an allocation at a fixed offset from the frame
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/// pointer.
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virtual void
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adjustForFrameAllocatePrologue(MachineFunction &MF,
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MachineBasicBlock &PrologueMBB) const {}
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/// spillCalleeSavedRegisters - Issues instruction(s) to spill all callee
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/// saved registers and returns true if it isn't possible / profitable to do
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/// so by issuing a series of store instructions via
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/// storeRegToStackSlot(). Returns false otherwise.
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virtual bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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const std::vector<CalleeSavedInfo> &CSI,
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const TargetRegisterInfo *TRI) const {
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return false;
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}
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/// restoreCalleeSavedRegisters - Issues instruction(s) to restore all callee
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/// saved registers and returns true if it isn't possible / profitable to do
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/// so by issuing a series of load instructions via loadRegToStackSlot().
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/// Returns false otherwise.
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virtual bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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const std::vector<CalleeSavedInfo> &CSI,
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const TargetRegisterInfo *TRI) const {
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return false;
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}
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/// Return true if the target needs to disable frame pointer elimination.
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virtual bool noFramePointerElim(const MachineFunction &MF) const;
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/// hasFP - Return true if the specified function should have a dedicated
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/// frame pointer register. For most targets this is true only if the function
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/// has variable sized allocas or if frame pointer elimination is disabled.
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virtual bool hasFP(const MachineFunction &MF) const = 0;
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/// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
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/// not required, we reserve argument space for call sites in the function
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/// immediately on entry to the current function. This eliminates the need for
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/// add/sub sp brackets around call sites. Returns true if the call frame is
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/// included as part of the stack frame.
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virtual bool hasReservedCallFrame(const MachineFunction &MF) const {
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return !hasFP(MF);
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}
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/// canSimplifyCallFramePseudos - When possible, it's best to simplify the
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/// call frame pseudo ops before doing frame index elimination. This is
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/// possible only when frame index references between the pseudos won't
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/// need adjusting for the call frame adjustments. Normally, that's true
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/// if the function has a reserved call frame or a frame pointer. Some
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/// targets (Thumb2, for example) may have more complicated criteria,
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/// however, and can override this behavior.
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virtual bool canSimplifyCallFramePseudos(const MachineFunction &MF) const {
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return hasReservedCallFrame(MF) || hasFP(MF);
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}
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// needsFrameIndexResolution - Do we need to perform FI resolution for
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// this function. Normally, this is required only when the function
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// has any stack objects. However, targets may want to override this.
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virtual bool needsFrameIndexResolution(const MachineFunction &MF) const;
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/// getFrameIndexOffset - Returns the displacement from the frame register to
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/// the stack frame of the specified index.
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virtual int getFrameIndexOffset(const MachineFunction &MF, int FI) const;
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/// getFrameIndexReference - This method should return the base register
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/// and offset used to reference a frame index location. The offset is
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/// returned directly, and the base register is returned via FrameReg.
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virtual int getFrameIndexReference(const MachineFunction &MF, int FI,
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unsigned &FrameReg) const;
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/// Same as above, except that the 'base register' will always be RSP, not
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/// RBP on x86. This is used exclusively for lowering STATEPOINT nodes.
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/// TODO: This should really be a parameterizable choice.
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virtual int getFrameIndexReferenceFromSP(const MachineFunction &MF, int FI,
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unsigned &FrameReg) const {
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// default to calling normal version, we override this on x86 only
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llvm_unreachable("unimplemented for non-x86");
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return 0;
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}
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/// This method determines which of the registers reported by
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/// TargetRegisterInfo::getCalleeSavedRegs() should actually get saved.
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/// The default implementation checks populates the \p SavedRegs bitset with
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/// all registers which are modified in the function, targets may override
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/// this function to save additional registers.
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/// This method also sets up the register scavenger ensuring there is a free
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/// register or a frameindex available.
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virtual void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
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RegScavenger *RS = nullptr) const;
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/// processFunctionBeforeFrameFinalized - This method is called immediately
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/// before the specified function's frame layout (MF.getFrameInfo()) is
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/// finalized. Once the frame is finalized, MO_FrameIndex operands are
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/// replaced with direct constants. This method is optional.
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///
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virtual void processFunctionBeforeFrameFinalized(MachineFunction &MF,
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RegScavenger *RS = nullptr) const {
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}
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/// eliminateCallFramePseudoInstr - This method is called during prolog/epilog
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/// code insertion to eliminate call frame setup and destroy pseudo
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/// instructions (but only if the Target is using them). It is responsible
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/// for eliminating these instructions, replacing them with concrete
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/// instructions. This method need only be implemented if using call frame
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/// setup/destroy pseudo instructions.
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///
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virtual void
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eliminateCallFramePseudoInstr(MachineFunction &MF,
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MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI) const {
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llvm_unreachable("Call Frame Pseudo Instructions do not exist on this "
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"target!");
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}
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/// Check whether or not the given \p MBB can be used as a prologue
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/// for the target.
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/// The prologue will be inserted first in this basic block.
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/// This method is used by the shrink-wrapping pass to decide if
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/// \p MBB will be correctly handled by the target.
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/// As soon as the target enable shrink-wrapping without overriding
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/// this method, we assume that each basic block is a valid
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/// prologue.
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virtual bool canUseAsPrologue(const MachineBasicBlock &MBB) const {
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return true;
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}
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/// Check whether or not the given \p MBB can be used as a epilogue
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/// for the target.
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/// The epilogue will be inserted before the first terminator of that block.
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/// This method is used by the shrink-wrapping pass to decide if
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/// \p MBB will be correctly handled by the target.
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/// As soon as the target enable shrink-wrapping without overriding
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/// this method, we assume that each basic block is a valid
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/// epilogue.
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virtual bool canUseAsEpilogue(const MachineBasicBlock &MBB) const {
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return true;
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}
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};
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} // End llvm namespace
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#endif
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