forked from OSchip/llvm-project
127 lines
5.0 KiB
C++
127 lines
5.0 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/MachineRegisterInfo.h"
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#include "llvm/CodeGen/TargetFrameLowering.h"
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#include "llvm/CodeGen/TargetRegisterInfo.h"
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#include "llvm/CodeGen/TargetSubtargetInfo.h"
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#include "llvm/IR/Attributes.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/MC/MCRegisterInfo.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetOptions.h"
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using namespace llvm;
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TargetFrameLowering::~TargetFrameLowering() = default;
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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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bool TargetFrameLowering::enableCalleeSaveSkip(const MachineFunction &MF) const {
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assert(MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
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MF.getFunction().hasFnAttribute(Attribute::NoUnwind) &&
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!MF.getFunction().hasFnAttribute(Attribute::UWTable));
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return false;
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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 (MF.getTarget().Options.EnableIPRA && 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 = MF.getRegInfo().getCalleeSavedRegs();
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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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// Noreturn+nounwind functions never restore CSR, so no saves are needed.
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// Purely noreturn functions may still return through throws, so those must
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// save CSR for caller exception handlers.
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//
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// If the function uses longjmp to break out of its current path of
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// execution we do not need the CSR spills either: setjmp stores all CSRs
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// it was called with into the jmp_buf, which longjmp then restores.
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if (MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
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MF.getFunction().hasFnAttribute(Attribute::NoUnwind) &&
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!MF.getFunction().hasFnAttribute(Attribute::UWTable) &&
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enableCalleeSaveSkip(MF))
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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.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().getAllocaPointerSize();
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return 0;
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}
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