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4beea66232
IPRA try to optimize caller saved register by propagating register usage information from callee to caller so it is beneficial to have caller saved registers compare to callee saved registers when IPRA is enabled. Please find more detailed explanation here https://groups.google.com/d/msg/llvm-dev/XRzGhJ9wtZg/tjAJqb0eEgAJ. This change makes local function do not have any callee preserved register when IPRA is enabled. A simple test case is also added to verify this change. Patch by Vivek Pandya <vivekvpandya@gmail.com> Differential Revision: http://reviews.llvm.org/D21561 llvm-svn: 275347
105 lines
3.9 KiB
C++
105 lines
3.9 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/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/CodeGen/TargetPassConfig.h"
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#include "llvm/IR/CallingConv.h"
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#include "llvm/IR/Function.h"
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#include "llvm/Target/TargetFrameLowering.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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/// Returns the displacement from the frame register to the stack
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/// frame of the specified index, along with the frame register used
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/// (in output arg FrameReg). This is the default implementation which
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/// is overridden for some targets.
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int TargetFrameLowering::getFrameIndexReference(const MachineFunction &MF,
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int FI, unsigned &FrameReg) const {
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const MachineFrameInfo *MFI = MF.getFrameInfo();
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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 MFI->getObjectOffset(FI) + MFI->getStackSize() -
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getOffsetOfLocalArea() + MFI->getOffsetAdjustment();
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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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const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
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// Resize before the early returns. Some backends expect that
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// SavedRegs.size() == TRI.getNumRegs() after this call even if there are no
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// saved registers.
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SavedRegs.resize(TRI.getNumRegs());
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// When interprocedural register allocation is enabled caller saved registers
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// are preferred over callee saved registers.
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if (UseIPRA && isSafeForNoCSROpt(MF.getFunction()))
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return;
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// Get the callee saved register list...
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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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// 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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unsigned TargetFrameLowering::getStackAlignmentSkew(
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const MachineFunction &MF) const {
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// When HHVM function is called, the stack is skewed as the return address
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// is removed from the stack before we enter the function.
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if (LLVM_UNLIKELY(MF.getFunction()->getCallingConv() == CallingConv::HHVM))
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return MF.getTarget().getPointerSize();
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return 0;
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}
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