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a36268215f
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
87 lines
3.3 KiB
C++
87 lines
3.3 KiB
C++
//===----- TargetFrameLoweringImpl.cpp - Implement target frame interface --==//
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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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// Implements the layout of a stack frame on the target machine.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/BitVector.h"
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#include "llvm/Target/TargetFrameLowering.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/IR/Function.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/Target/TargetSubtargetInfo.h"
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#include <cstdlib>
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using namespace llvm;
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TargetFrameLowering::~TargetFrameLowering() {
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}
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/// The default implementation just looks at attribute "no-frame-pointer-elim".
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bool TargetFrameLowering::noFramePointerElim(const MachineFunction &MF) const {
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auto Attr = MF.getFunction()->getFnAttribute("no-frame-pointer-elim");
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return Attr.getValueAsString() == "true";
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}
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/// getFrameIndexOffset - Returns the displacement from the frame register to
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/// the stack frame of the specified index. This is the default implementation
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/// which is overridden for some targets.
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int TargetFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
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int FI) const {
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const MachineFrameInfo *MFI = MF.getFrameInfo();
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return MFI->getObjectOffset(FI) + MFI->getStackSize() -
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getOffsetOfLocalArea() + MFI->getOffsetAdjustment();
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}
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int TargetFrameLowering::getFrameIndexReference(const MachineFunction &MF,
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int FI, unsigned &FrameReg) const {
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const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo();
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// By default, assume all frame indices are referenced via whatever
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// getFrameRegister() says. The target can override this if it's doing
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// something different.
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FrameReg = RI->getFrameRegister(MF);
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return getFrameIndexOffset(MF, FI);
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}
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bool TargetFrameLowering::needsFrameIndexResolution(
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const MachineFunction &MF) const {
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return MF.getFrameInfo()->hasStackObjects();
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}
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void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF,
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BitVector &SavedRegs,
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RegScavenger *RS) const {
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// Get the callee saved register list...
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const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
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const MCPhysReg *CSRegs = TRI.getCalleeSavedRegs(&MF);
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// Early exit if there are no callee saved registers.
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if (!CSRegs || CSRegs[0] == 0)
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return;
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SavedRegs.resize(TRI.getNumRegs());
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// In Naked functions we aren't going to save any registers.
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if (MF.getFunction()->hasFnAttribute(Attribute::Naked))
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return;
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// Functions which call __builtin_unwind_init get all their registers saved.
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bool CallsUnwindInit = MF.getMMI().callsUnwindInit();
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const MachineRegisterInfo &MRI = MF.getRegInfo();
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for (unsigned i = 0; CSRegs[i]; ++i) {
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unsigned Reg = CSRegs[i];
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if (CallsUnwindInit || MRI.isPhysRegModified(Reg))
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SavedRegs.set(Reg);
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}
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}
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