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llvm/lib/Target/ARM/ARMFrameLowering.cpp
Stepan Dyatkovskiy 083bc97344 PR15868 fix. 
Introduction:
In case when stack alignment is 8 and GPRs parameter part size is not N*8:
we add padding to GPRs part, so part's last byte must be recovered at
address K*8-1.
We need to do it, since remained (stack) part of parameter starts from
address K*8, and we need to "attach" "GPRs head" without gaps to it:

Stack:
|---- 8 bytes block ----| |---- 8 bytes block ----| |---- 8 bytes...
[ [padding] [GPRs head] ] [ ------ Tail passed via stack  ------ ...

FIX:
Note, once we added padding we need to correct *all* Arg offsets that are going
after padded one. That's why we need this fix: Arg offsets were never corrected
before this patch. See new test-cases included in patch.

We also don't need to insert padding for byval parameters that are stored in GPRs
only. We need pad only last byval parameter and only in case it outsides GPRs
and stack alignment = 8.
Though, stack area, allocated for recovered byval params, must satisfy
"Size mod 8 = 0" restriction.

This patch reduces stack usage for some cases:
We can reduce ArgRegsSaveArea since inner N*4 bytes sized byval params my be
"packed" with alignment 4 in some cases.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182237 91177308-0d34-0410-b5e6-96231b3b80d8
2013-05-20 08:01:34 +00:00

1433 lines
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//===-- ARMFrameLowering.cpp - ARM Frame Information ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the ARM implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "ARMFrameLowering.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBaseRegisterInfo.h"
#include "ARMMachineFunctionInfo.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
static cl::opt<bool>
SpillAlignedNEONRegs("align-neon-spills", cl::Hidden, cl::init(true),
cl::desc("Align ARM NEON spills in prolog and epilog"));
static MachineBasicBlock::iterator
skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs);
/// hasFP - Return true if the specified function should have a dedicated frame
/// pointer register. This is true if the function has variable sized allocas
/// or if frame pointer elimination is disabled.
bool ARMFrameLowering::hasFP(const MachineFunction &MF) const {
const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
// iOS requires FP not to be clobbered for backtracing purpose.
if (STI.isTargetIOS())
return true;
const MachineFrameInfo *MFI = MF.getFrameInfo();
// Always eliminate non-leaf frame pointers.
return ((MF.getTarget().Options.DisableFramePointerElim(MF) &&
MFI->hasCalls()) ||
RegInfo->needsStackRealignment(MF) ||
MFI->hasVarSizedObjects() ||
MFI->isFrameAddressTaken());
}
/// 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.
bool ARMFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
const MachineFrameInfo *FFI = MF.getFrameInfo();
unsigned CFSize = FFI->getMaxCallFrameSize();
// It's not always a good idea to include the call frame as part of the
// stack frame. ARM (especially Thumb) has small immediate offset to
// address the stack frame. So a large call frame can cause poor codegen
// and may even makes it impossible to scavenge a register.
if (CFSize >= ((1 << 12) - 1) / 2) // Half of imm12
return false;
return !MF.getFrameInfo()->hasVarSizedObjects();
}
/// canSimplifyCallFramePseudos - If there is a reserved call frame, the
/// call frame pseudos can be simplified. Unlike most targets, having a FP
/// is not sufficient here since we still may reference some objects via SP
/// even when FP is available in Thumb2 mode.
bool
ARMFrameLowering::canSimplifyCallFramePseudos(const MachineFunction &MF) const {
return hasReservedCallFrame(MF) || MF.getFrameInfo()->hasVarSizedObjects();
}
static bool isCalleeSavedRegister(unsigned Reg, const uint16_t *CSRegs) {
for (unsigned i = 0; CSRegs[i]; ++i)
if (Reg == CSRegs[i])
return true;
return false;
}
static bool isCSRestore(MachineInstr *MI,
const ARMBaseInstrInfo &TII,
const uint16_t *CSRegs) {
// Integer spill area is handled with "pop".
if (MI->getOpcode() == ARM::LDMIA_RET ||
MI->getOpcode() == ARM::t2LDMIA_RET ||
MI->getOpcode() == ARM::LDMIA_UPD ||
MI->getOpcode() == ARM::t2LDMIA_UPD ||
MI->getOpcode() == ARM::VLDMDIA_UPD) {
// The first two operands are predicates. The last two are
// imp-def and imp-use of SP. Check everything in between.
for (int i = 5, e = MI->getNumOperands(); i != e; ++i)
if (!isCalleeSavedRegister(MI->getOperand(i).getReg(), CSRegs))
return false;
return true;
}
if ((MI->getOpcode() == ARM::LDR_POST_IMM ||
MI->getOpcode() == ARM::LDR_POST_REG ||
MI->getOpcode() == ARM::t2LDR_POST) &&
isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs) &&
MI->getOperand(1).getReg() == ARM::SP)
return true;
return false;
}
static void
emitSPUpdate(bool isARM,
MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
DebugLoc dl, const ARMBaseInstrInfo &TII,
int NumBytes, unsigned MIFlags = MachineInstr::NoFlags,
ARMCC::CondCodes Pred = ARMCC::AL, unsigned PredReg = 0) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes,
Pred, PredReg, TII, MIFlags);
else
emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes,
Pred, PredReg, TII, MIFlags);
}
void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front();
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
assert(!AFI->isThumb1OnlyFunction() &&
"This emitPrologue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
unsigned Align = MF.getTarget().getFrameLowering()->getStackAlignment();
unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align);
unsigned NumBytes = MFI->getStackSize();
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
// Determine the sizes of each callee-save spill areas and record which frame
// belongs to which callee-save spill areas.
unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0;
int FramePtrSpillFI = 0;
int D8SpillFI = 0;
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction()->getCallingConv() == CallingConv::GHC)
return;
// Allocate the vararg register save area. This is not counted in NumBytes.
if (ArgRegsSaveSize)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -ArgRegsSaveSize,
MachineInstr::FrameSetup);
if (!AFI->hasStackFrame()) {
if (NumBytes != 0)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
MachineInstr::FrameSetup);
return;
}
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
int FI = CSI[i].getFrameIdx();
switch (Reg) {
case ARM::R4:
case ARM::R5:
case ARM::R6:
case ARM::R7:
case ARM::LR:
if (Reg == FramePtr)
FramePtrSpillFI = FI;
AFI->addGPRCalleeSavedArea1Frame(FI);
GPRCS1Size += 4;
break;
case ARM::R8:
case ARM::R9:
case ARM::R10:
case ARM::R11:
if (Reg == FramePtr)
FramePtrSpillFI = FI;
if (STI.isTargetIOS()) {
AFI->addGPRCalleeSavedArea2Frame(FI);
GPRCS2Size += 4;
} else {
AFI->addGPRCalleeSavedArea1Frame(FI);
GPRCS1Size += 4;
}
break;
default:
// This is a DPR. Exclude the aligned DPRCS2 spills.
if (Reg == ARM::D8)
D8SpillFI = FI;
if (Reg < ARM::D8 || Reg >= ARM::D8 + AFI->getNumAlignedDPRCS2Regs()) {
AFI->addDPRCalleeSavedAreaFrame(FI);
DPRCSSize += 8;
}
}
}
// Move past area 1.
if (GPRCS1Size > 0) MBBI++;
// Set FP to point to the stack slot that contains the previous FP.
// For iOS, FP is R7, which has now been stored in spill area 1.
// Otherwise, if this is not iOS, all the callee-saved registers go
// into spill area 1, including the FP in R11. In either case, it is
// now safe to emit this assignment.
bool HasFP = hasFP(MF);
if (HasFP) {
unsigned ADDriOpc = !AFI->isThumbFunction() ? ARM::ADDri : ARM::t2ADDri;
MachineInstrBuilder MIB =
BuildMI(MBB, MBBI, dl, TII.get(ADDriOpc), FramePtr)
.addFrameIndex(FramePtrSpillFI).addImm(0)
.setMIFlag(MachineInstr::FrameSetup);
AddDefaultCC(AddDefaultPred(MIB));
}
// Move past area 2.
if (GPRCS2Size > 0) MBBI++;
// Determine starting offsets of spill areas.
unsigned DPRCSOffset = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize);
unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size;
if (HasFP)
AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) +
NumBytes);
AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
// Move past area 3.
if (DPRCSSize > 0) {
MBBI++;
// Since vpush register list cannot have gaps, there may be multiple vpush
// instructions in the prologue.
while (MBBI->getOpcode() == ARM::VSTMDDB_UPD)
MBBI++;
}
// Move past the aligned DPRCS2 area.
if (AFI->getNumAlignedDPRCS2Regs() > 0) {
MBBI = skipAlignedDPRCS2Spills(MBBI, AFI->getNumAlignedDPRCS2Regs());
// The code inserted by emitAlignedDPRCS2Spills realigns the stack, and
// leaves the stack pointer pointing to the DPRCS2 area.
//
// Adjust NumBytes to represent the stack slots below the DPRCS2 area.
NumBytes += MFI->getObjectOffset(D8SpillFI);
} else
NumBytes = DPRCSOffset;
if (NumBytes) {
// Adjust SP after all the callee-save spills.
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
MachineInstr::FrameSetup);
if (HasFP && isARM)
// Restore from fp only in ARM mode: e.g. sub sp, r7, #24
// Note it's not safe to do this in Thumb2 mode because it would have
// taken two instructions:
// mov sp, r7
// sub sp, #24
// If an interrupt is taken between the two instructions, then sp is in
// an inconsistent state (pointing to the middle of callee-saved area).
// The interrupt handler can end up clobbering the registers.
AFI->setShouldRestoreSPFromFP(true);
}
if (STI.isTargetELF() && hasFP(MF))
MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() -
AFI->getFramePtrSpillOffset());
AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
// If we need dynamic stack realignment, do it here. Be paranoid and make
// sure if we also have VLAs, we have a base pointer for frame access.
// If aligned NEON registers were spilled, the stack has already been
// realigned.
if (!AFI->getNumAlignedDPRCS2Regs() && RegInfo->needsStackRealignment(MF)) {
unsigned MaxAlign = MFI->getMaxAlignment();
assert (!AFI->isThumb1OnlyFunction());
if (!AFI->isThumbFunction()) {
// Emit bic sp, sp, MaxAlign
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
TII.get(ARM::BICri), ARM::SP)
.addReg(ARM::SP, RegState::Kill)
.addImm(MaxAlign-1)));
} else {
// We cannot use sp as source/dest register here, thus we're emitting the
// following sequence:
// mov r4, sp
// bic r4, r4, MaxAlign
// mov sp, r4
// FIXME: It will be better just to find spare register here.
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4)
.addReg(ARM::SP, RegState::Kill));
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
TII.get(ARM::t2BICri), ARM::R4)
.addReg(ARM::R4, RegState::Kill)
.addImm(MaxAlign-1)));
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(ARM::R4, RegState::Kill));
}
AFI->setShouldRestoreSPFromFP(true);
}
// If we need a base pointer, set it up here. It's whatever the value
// of the stack pointer is at this point. Any variable size objects
// will be allocated after this, so we can still use the base pointer
// to reference locals.
// FIXME: Clarify FrameSetup flags here.
if (RegInfo->hasBasePointer(MF)) {
if (isARM)
BuildMI(MBB, MBBI, dl,
TII.get(ARM::MOVr), RegInfo->getBaseRegister())
.addReg(ARM::SP)
.addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
else
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
RegInfo->getBaseRegister())
.addReg(ARM::SP));
}
// If the frame has variable sized objects then the epilogue must restore
// the sp from fp. We can assume there's an FP here since hasFP already
// checks for hasVarSizedObjects.
if (MFI->hasVarSizedObjects())
AFI->setShouldRestoreSPFromFP(true);
}
void ARMFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
assert(MBBI->isReturn() && "Can only insert epilog into returning blocks");
unsigned RetOpcode = MBBI->getOpcode();
DebugLoc dl = MBBI->getDebugLoc();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
assert(!AFI->isThumb1OnlyFunction() &&
"This emitEpilogue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
unsigned Align = MF.getTarget().getFrameLowering()->getStackAlignment();
unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align);
int NumBytes = (int)MFI->getStackSize();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction()->getCallingConv() == CallingConv::GHC)
return;
if (!AFI->hasStackFrame()) {
if (NumBytes != 0)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes);
} else {
// Unwind MBBI to point to first LDR / VLDRD.
const uint16_t *CSRegs = RegInfo->getCalleeSavedRegs();
if (MBBI != MBB.begin()) {
do
--MBBI;
while (MBBI != MBB.begin() && isCSRestore(MBBI, TII, CSRegs));
if (!isCSRestore(MBBI, TII, CSRegs))
++MBBI;
}
// Move SP to start of FP callee save spill area.
NumBytes -= (AFI->getGPRCalleeSavedArea1Size() +
AFI->getGPRCalleeSavedArea2Size() +
AFI->getDPRCalleeSavedAreaSize());
// Reset SP based on frame pointer only if the stack frame extends beyond
// frame pointer stack slot or target is ELF and the function has FP.
if (AFI->shouldRestoreSPFromFP()) {
NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
if (NumBytes) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, FramePtr, -NumBytes,
ARMCC::AL, 0, TII);
else {
// It's not possible to restore SP from FP in a single instruction.
// For iOS, this looks like:
// mov sp, r7
// sub sp, #24
// This is bad, if an interrupt is taken after the mov, sp is in an
// inconsistent state.
// Use the first callee-saved register as a scratch register.
assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
"No scratch register to restore SP from FP!");
emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes,
ARMCC::AL, 0, TII);
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
ARM::SP)
.addReg(ARM::R4));
}
} else {
// Thumb2 or ARM.
if (isARM)
BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), ARM::SP)
.addReg(FramePtr).addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
else
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
ARM::SP)
.addReg(FramePtr));
}
} else if (NumBytes)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes);
// Increment past our save areas.
if (AFI->getDPRCalleeSavedAreaSize()) {
MBBI++;
// Since vpop register list cannot have gaps, there may be multiple vpop
// instructions in the epilogue.
while (MBBI->getOpcode() == ARM::VLDMDIA_UPD)
MBBI++;
}
if (AFI->getGPRCalleeSavedArea2Size()) MBBI++;
if (AFI->getGPRCalleeSavedArea1Size()) MBBI++;
}
if (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNri) {
// Tail call return: adjust the stack pointer and jump to callee.
MBBI = MBB.getLastNonDebugInstr();
MachineOperand &JumpTarget = MBBI->getOperand(0);
// Jump to label or value in register.
if (RetOpcode == ARM::TCRETURNdi) {
unsigned TCOpcode = STI.isThumb() ?
(STI.isTargetIOS() ? ARM::tTAILJMPd : ARM::tTAILJMPdND) :
ARM::TAILJMPd;
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(TCOpcode));
if (JumpTarget.isGlobal())
MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
JumpTarget.getTargetFlags());
else {
assert(JumpTarget.isSymbol());
MIB.addExternalSymbol(JumpTarget.getSymbolName(),
JumpTarget.getTargetFlags());
}
// Add the default predicate in Thumb mode.
if (STI.isThumb()) MIB.addImm(ARMCC::AL).addReg(0);
} else if (RetOpcode == ARM::TCRETURNri) {
BuildMI(MBB, MBBI, dl,
TII.get(STI.isThumb() ? ARM::tTAILJMPr : ARM::TAILJMPr)).
addReg(JumpTarget.getReg(), RegState::Kill);
}
MachineInstr *NewMI = prior(MBBI);
for (unsigned i = 1, e = MBBI->getNumOperands(); i != e; ++i)
NewMI->addOperand(MBBI->getOperand(i));
// Delete the pseudo instruction TCRETURN.
MBB.erase(MBBI);
MBBI = NewMI;
}
if (ArgRegsSaveSize)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, ArgRegsSaveSize);
}
/// getFrameIndexReference - Provide a base+offset reference to an FI slot for
/// debug info. It's the same as what we use for resolving the code-gen
/// references for now. FIXME: This can go wrong when references are
/// SP-relative and simple call frames aren't used.
int
ARMFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
unsigned &FrameReg) const {
return ResolveFrameIndexReference(MF, FI, FrameReg, 0);
}
int
ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF,
int FI, unsigned &FrameReg,
int SPAdj) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
int Offset = MFI->getObjectOffset(FI) + MFI->getStackSize();
int FPOffset = Offset - AFI->getFramePtrSpillOffset();
bool isFixed = MFI->isFixedObjectIndex(FI);
FrameReg = ARM::SP;
Offset += SPAdj;
if (AFI->isGPRCalleeSavedArea1Frame(FI))
return Offset - AFI->getGPRCalleeSavedArea1Offset();
else if (AFI->isGPRCalleeSavedArea2Frame(FI))
return Offset - AFI->getGPRCalleeSavedArea2Offset();
else if (AFI->isDPRCalleeSavedAreaFrame(FI))
return Offset - AFI->getDPRCalleeSavedAreaOffset();
// SP can move around if there are allocas. We may also lose track of SP
// when emergency spilling inside a non-reserved call frame setup.
bool hasMovingSP = !hasReservedCallFrame(MF);
// When dynamically realigning the stack, use the frame pointer for
// parameters, and the stack/base pointer for locals.
if (RegInfo->needsStackRealignment(MF)) {
assert (hasFP(MF) && "dynamic stack realignment without a FP!");
if (isFixed) {
FrameReg = RegInfo->getFrameRegister(MF);
Offset = FPOffset;
} else if (hasMovingSP) {
assert(RegInfo->hasBasePointer(MF) &&
"VLAs and dynamic stack alignment, but missing base pointer!");
FrameReg = RegInfo->getBaseRegister();
}
return Offset;
}
// If there is a frame pointer, use it when we can.
if (hasFP(MF) && AFI->hasStackFrame()) {
// Use frame pointer to reference fixed objects. Use it for locals if
// there are VLAs (and thus the SP isn't reliable as a base).
if (isFixed || (hasMovingSP && !RegInfo->hasBasePointer(MF))) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
} else if (hasMovingSP) {
assert(RegInfo->hasBasePointer(MF) && "missing base pointer!");
if (AFI->isThumb2Function()) {
// Try to use the frame pointer if we can, else use the base pointer
// since it's available. This is handy for the emergency spill slot, in
// particular.
if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
}
} else if (AFI->isThumb2Function()) {
// Use add <rd>, sp, #<imm8>
// ldr <rd>, [sp, #<imm8>]
// if at all possible to save space.
if (Offset >= 0 && (Offset & 3) == 0 && Offset <= 1020)
return Offset;
// In Thumb2 mode, the negative offset is very limited. Try to avoid
// out of range references. ldr <rt>,[<rn>, #-<imm8>]
if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
} else if (Offset > (FPOffset < 0 ? -FPOffset : FPOffset)) {
// Otherwise, use SP or FP, whichever is closer to the stack slot.
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
}
// Use the base pointer if we have one.
if (RegInfo->hasBasePointer(MF))
FrameReg = RegInfo->getBaseRegister();
return Offset;
}
int ARMFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
int FI) const {
unsigned FrameReg;
return getFrameIndexReference(MF, FI, FrameReg);
}
void ARMFrameLowering::emitPushInst(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
unsigned StmOpc, unsigned StrOpc,
bool NoGap,
bool(*Func)(unsigned, bool),
unsigned NumAlignedDPRCS2Regs,
unsigned MIFlags) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
DebugLoc DL;
if (MI != MBB.end()) DL = MI->getDebugLoc();
SmallVector<std::pair<unsigned,bool>, 4> Regs;
unsigned i = CSI.size();
while (i != 0) {
unsigned LastReg = 0;
for (; i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (!(Func)(Reg, STI.isTargetIOS())) continue;
// D-registers in the aligned area DPRCS2 are NOT spilled here.
if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
continue;
// Add the callee-saved register as live-in unless it's LR and
// @llvm.returnaddress is called. If LR is returned for
// @llvm.returnaddress then it's already added to the function and
// entry block live-in sets.
bool isKill = true;
if (Reg == ARM::LR) {
if (MF.getFrameInfo()->isReturnAddressTaken() &&
MF.getRegInfo().isLiveIn(Reg))
isKill = false;
}
if (isKill)
MBB.addLiveIn(Reg);
// If NoGap is true, push consecutive registers and then leave the rest
// for other instructions. e.g.
// vpush {d8, d10, d11} -> vpush {d8}, vpush {d10, d11}
if (NoGap && LastReg && LastReg != Reg-1)
break;
LastReg = Reg;
Regs.push_back(std::make_pair(Reg, isKill));
}
if (Regs.empty())
continue;
if (Regs.size() > 1 || StrOpc== 0) {
MachineInstrBuilder MIB =
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(StmOpc), ARM::SP)
.addReg(ARM::SP).setMIFlags(MIFlags));
for (unsigned i = 0, e = Regs.size(); i < e; ++i)
MIB.addReg(Regs[i].first, getKillRegState(Regs[i].second));
} else if (Regs.size() == 1) {
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(StrOpc),
ARM::SP)
.addReg(Regs[0].first, getKillRegState(Regs[0].second))
.addReg(ARM::SP).setMIFlags(MIFlags)
.addImm(-4);
AddDefaultPred(MIB);
}
Regs.clear();
}
}
void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
unsigned LdmOpc, unsigned LdrOpc,
bool isVarArg, bool NoGap,
bool(*Func)(unsigned, bool),
unsigned NumAlignedDPRCS2Regs) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI->getDebugLoc();
unsigned RetOpcode = MI->getOpcode();
bool isTailCall = (RetOpcode == ARM::TCRETURNdi ||
RetOpcode == ARM::TCRETURNri);
SmallVector<unsigned, 4> Regs;
unsigned i = CSI.size();
while (i != 0) {
unsigned LastReg = 0;
bool DeleteRet = false;
for (; i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (!(Func)(Reg, STI.isTargetIOS())) continue;
// The aligned reloads from area DPRCS2 are not inserted here.
if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
continue;
if (Reg == ARM::LR && !isTailCall && !isVarArg && STI.hasV5TOps()) {
Reg = ARM::PC;
LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
// Fold the return instruction into the LDM.
DeleteRet = true;
}
// If NoGap is true, pop consecutive registers and then leave the rest
// for other instructions. e.g.
// vpop {d8, d10, d11} -> vpop {d8}, vpop {d10, d11}
if (NoGap && LastReg && LastReg != Reg-1)
break;
LastReg = Reg;
Regs.push_back(Reg);
}
if (Regs.empty())
continue;
if (Regs.size() > 1 || LdrOpc == 0) {
MachineInstrBuilder MIB =
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(LdmOpc), ARM::SP)
.addReg(ARM::SP));
for (unsigned i = 0, e = Regs.size(); i < e; ++i)
MIB.addReg(Regs[i], getDefRegState(true));
if (DeleteRet) {
MIB.copyImplicitOps(&*MI);
MI->eraseFromParent();
}
MI = MIB;
} else if (Regs.size() == 1) {
// If we adjusted the reg to PC from LR above, switch it back here. We
// only do that for LDM.
if (Regs[0] == ARM::PC)
Regs[0] = ARM::LR;
MachineInstrBuilder MIB =
BuildMI(MBB, MI, DL, TII.get(LdrOpc), Regs[0])
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP);
// ARM mode needs an extra reg0 here due to addrmode2. Will go away once
// that refactoring is complete (eventually).
if (LdrOpc == ARM::LDR_POST_REG || LdrOpc == ARM::LDR_POST_IMM) {
MIB.addReg(0);
MIB.addImm(ARM_AM::getAM2Opc(ARM_AM::add, 4, ARM_AM::no_shift));
} else
MIB.addImm(4);
AddDefaultPred(MIB);
}
Regs.clear();
}
}
/// Emit aligned spill instructions for NumAlignedDPRCS2Regs D-registers
/// starting from d8. Also insert stack realignment code and leave the stack
/// pointer pointing to the d8 spill slot.
static void emitAlignedDPRCS2Spills(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI->getDebugLoc();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
MachineFrameInfo &MFI = *MF.getFrameInfo();
// Mark the D-register spill slots as properly aligned. Since MFI computes
// stack slot layout backwards, this can actually mean that the d-reg stack
// slot offsets can be wrong. The offset for d8 will always be correct.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned DNum = CSI[i].getReg() - ARM::D8;
if (DNum >= 8)
continue;
int FI = CSI[i].getFrameIdx();
// The even-numbered registers will be 16-byte aligned, the odd-numbered
// registers will be 8-byte aligned.
MFI.setObjectAlignment(FI, DNum % 2 ? 8 : 16);
// The stack slot for D8 needs to be maximally aligned because this is
// actually the point where we align the stack pointer. MachineFrameInfo
// computes all offsets relative to the incoming stack pointer which is a
// bit weird when realigning the stack. Any extra padding for this
// over-alignment is not realized because the code inserted below adjusts
// the stack pointer by numregs * 8 before aligning the stack pointer.
if (DNum == 0)
MFI.setObjectAlignment(FI, MFI.getMaxAlignment());
}
// Move the stack pointer to the d8 spill slot, and align it at the same
// time. Leave the stack slot address in the scratch register r4.
//
// sub r4, sp, #numregs * 8
// bic r4, r4, #align - 1
// mov sp, r4
//
bool isThumb = AFI->isThumbFunction();
assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1");
AFI->setShouldRestoreSPFromFP(true);
// sub r4, sp, #numregs * 8
// The immediate is <= 64, so it doesn't need any special encoding.
unsigned Opc = isThumb ? ARM::t2SUBri : ARM::SUBri;
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addReg(ARM::SP)
.addImm(8 * NumAlignedDPRCS2Regs)));
// bic r4, r4, #align-1
Opc = isThumb ? ARM::t2BICri : ARM::BICri;
unsigned MaxAlign = MF.getFrameInfo()->getMaxAlignment();
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addReg(ARM::R4, RegState::Kill)
.addImm(MaxAlign - 1)));
// mov sp, r4
// The stack pointer must be adjusted before spilling anything, otherwise
// the stack slots could be clobbered by an interrupt handler.
// Leave r4 live, it is used below.
Opc = isThumb ? ARM::tMOVr : ARM::MOVr;
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(Opc), ARM::SP)
.addReg(ARM::R4);
MIB = AddDefaultPred(MIB);
if (!isThumb)
AddDefaultCC(MIB);
// Now spill NumAlignedDPRCS2Regs registers starting from d8.
// r4 holds the stack slot address.
unsigned NextReg = ARM::D8;
// 16-byte aligned vst1.64 with 4 d-regs and address writeback.
// The writeback is only needed when emitting two vst1.64 instructions.
if (NumAlignedDPRCS2Regs >= 6) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QQPRRegClass);
MBB.addLiveIn(SupReg);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Qwb_fixed),
ARM::R4)
.addReg(ARM::R4, RegState::Kill).addImm(16)
.addReg(NextReg)
.addReg(SupReg, RegState::ImplicitKill));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// We won't modify r4 beyond this point. It currently points to the next
// register to be spilled.
unsigned R4BaseReg = NextReg;
// 16-byte aligned vst1.64 with 4 d-regs, no writeback.
if (NumAlignedDPRCS2Regs >= 4) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QQPRRegClass);
MBB.addLiveIn(SupReg);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Q))
.addReg(ARM::R4).addImm(16).addReg(NextReg)
.addReg(SupReg, RegState::ImplicitKill));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// 16-byte aligned vst1.64 with 2 d-regs.
if (NumAlignedDPRCS2Regs >= 2) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QPRRegClass);
MBB.addLiveIn(SupReg);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1q64))
.addReg(ARM::R4).addImm(16).addReg(SupReg));
NextReg += 2;
NumAlignedDPRCS2Regs -= 2;
}
// Finally, use a vanilla vstr.64 for the odd last register.
if (NumAlignedDPRCS2Regs) {
MBB.addLiveIn(NextReg);
// vstr.64 uses addrmode5 which has an offset scale of 4.
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VSTRD))
.addReg(NextReg)
.addReg(ARM::R4).addImm((NextReg-R4BaseReg)*2));
}
// The last spill instruction inserted should kill the scratch register r4.
llvm::prior(MI)->addRegisterKilled(ARM::R4, TRI);
}
/// Skip past the code inserted by emitAlignedDPRCS2Spills, and return an
/// iterator to the following instruction.
static MachineBasicBlock::iterator
skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs) {
// sub r4, sp, #numregs * 8
// bic r4, r4, #align - 1
// mov sp, r4
++MI; ++MI; ++MI;
assert(MI->mayStore() && "Expecting spill instruction");
// These switches all fall through.
switch(NumAlignedDPRCS2Regs) {
case 7:
++MI;
assert(MI->mayStore() && "Expecting spill instruction");
default:
++MI;
assert(MI->mayStore() && "Expecting spill instruction");
case 1:
case 2:
case 4:
assert(MI->killsRegister(ARM::R4) && "Missed kill flag");
++MI;
}
return MI;
}
/// Emit aligned reload instructions for NumAlignedDPRCS2Regs D-registers
/// starting from d8. These instructions are assumed to execute while the
/// stack is still aligned, unlike the code inserted by emitPopInst.
static void emitAlignedDPRCS2Restores(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI->getDebugLoc();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
// Find the frame index assigned to d8.
int D8SpillFI = 0;
for (unsigned i = 0, e = CSI.size(); i != e; ++i)
if (CSI[i].getReg() == ARM::D8) {
D8SpillFI = CSI[i].getFrameIdx();
break;
}
// Materialize the address of the d8 spill slot into the scratch register r4.
// This can be fairly complicated if the stack frame is large, so just use
// the normal frame index elimination mechanism to do it. This code runs as
// the initial part of the epilog where the stack and base pointers haven't
// been changed yet.
bool isThumb = AFI->isThumbFunction();
assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1");
unsigned Opc = isThumb ? ARM::t2ADDri : ARM::ADDri;
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addFrameIndex(D8SpillFI).addImm(0)));
// Now restore NumAlignedDPRCS2Regs registers starting from d8.
unsigned NextReg = ARM::D8;
// 16-byte aligned vld1.64 with 4 d-regs and writeback.
if (NumAlignedDPRCS2Regs >= 6) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QQPRRegClass);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Qwb_fixed), NextReg)
.addReg(ARM::R4, RegState::Define)
.addReg(ARM::R4, RegState::Kill).addImm(16)
.addReg(SupReg, RegState::ImplicitDefine));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// We won't modify r4 beyond this point. It currently points to the next
// register to be spilled.
unsigned R4BaseReg = NextReg;
// 16-byte aligned vld1.64 with 4 d-regs, no writeback.
if (NumAlignedDPRCS2Regs >= 4) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QQPRRegClass);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Q), NextReg)
.addReg(ARM::R4).addImm(16)
.addReg(SupReg, RegState::ImplicitDefine));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// 16-byte aligned vld1.64 with 2 d-regs.
if (NumAlignedDPRCS2Regs >= 2) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QPRRegClass);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1q64), SupReg)
.addReg(ARM::R4).addImm(16));
NextReg += 2;
NumAlignedDPRCS2Regs -= 2;
}
// Finally, use a vanilla vldr.64 for the remaining odd register.
if (NumAlignedDPRCS2Regs)
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLDRD), NextReg)
.addReg(ARM::R4).addImm(2*(NextReg-R4BaseReg)));
// Last store kills r4.
llvm::prior(MI)->addRegisterKilled(ARM::R4, TRI);
}
bool ARMFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
unsigned PushOpc = AFI->isThumbFunction() ? ARM::t2STMDB_UPD : ARM::STMDB_UPD;
unsigned PushOneOpc = AFI->isThumbFunction() ?
ARM::t2STR_PRE : ARM::STR_PRE_IMM;
unsigned FltOpc = ARM::VSTMDDB_UPD;
unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs();
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea1Register, 0,
MachineInstr::FrameSetup);
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea2Register, 0,
MachineInstr::FrameSetup);
emitPushInst(MBB, MI, CSI, FltOpc, 0, true, &isARMArea3Register,
NumAlignedDPRCS2Regs, MachineInstr::FrameSetup);
// The code above does not insert spill code for the aligned DPRCS2 registers.
// The stack realignment code will be inserted between the push instructions
// and these spills.
if (NumAlignedDPRCS2Regs)
emitAlignedDPRCS2Spills(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI);
return true;
}
bool ARMFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
bool isVarArg = AFI->getArgRegsSaveSize() > 0;
unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs();
// The emitPopInst calls below do not insert reloads for the aligned DPRCS2
// registers. Do that here instead.
if (NumAlignedDPRCS2Regs)
emitAlignedDPRCS2Restores(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI);
unsigned PopOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD;
unsigned LdrOpc = AFI->isThumbFunction() ? ARM::t2LDR_POST :ARM::LDR_POST_IMM;
unsigned FltOpc = ARM::VLDMDIA_UPD;
emitPopInst(MBB, MI, CSI, FltOpc, 0, isVarArg, true, &isARMArea3Register,
NumAlignedDPRCS2Regs);
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false,
&isARMArea2Register, 0);
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false,
&isARMArea1Register, 0);
return true;
}
// FIXME: Make generic?
static unsigned GetFunctionSizeInBytes(const MachineFunction &MF,
const ARMBaseInstrInfo &TII) {
unsigned FnSize = 0;
for (MachineFunction::const_iterator MBBI = MF.begin(), E = MF.end();
MBBI != E; ++MBBI) {
const MachineBasicBlock &MBB = *MBBI;
for (MachineBasicBlock::const_iterator I = MBB.begin(),E = MBB.end();
I != E; ++I)
FnSize += TII.GetInstSizeInBytes(I);
}
return FnSize;
}
/// estimateRSStackSizeLimit - Look at each instruction that references stack
/// frames and return the stack size limit beyond which some of these
/// instructions will require a scratch register during their expansion later.
// FIXME: Move to TII?
static unsigned estimateRSStackSizeLimit(MachineFunction &MF,
const TargetFrameLowering *TFI) {
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
unsigned Limit = (1 << 12) - 1;
for (MachineFunction::iterator BB = MF.begin(),E = MF.end(); BB != E; ++BB) {
for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
I != E; ++I) {
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
if (!I->getOperand(i).isFI()) continue;
// When using ADDri to get the address of a stack object, 255 is the
// largest offset guaranteed to fit in the immediate offset.
if (I->getOpcode() == ARM::ADDri) {
Limit = std::min(Limit, (1U << 8) - 1);
break;
}
// Otherwise check the addressing mode.
switch (I->getDesc().TSFlags & ARMII::AddrModeMask) {
case ARMII::AddrMode3:
case ARMII::AddrModeT2_i8:
Limit = std::min(Limit, (1U << 8) - 1);
break;
case ARMII::AddrMode5:
case ARMII::AddrModeT2_i8s4:
Limit = std::min(Limit, ((1U << 8) - 1) * 4);
break;
case ARMII::AddrModeT2_i12:
// i12 supports only positive offset so these will be converted to
// i8 opcodes. See llvm::rewriteT2FrameIndex.
if (TFI->hasFP(MF) && AFI->hasStackFrame())
Limit = std::min(Limit, (1U << 8) - 1);
break;
case ARMII::AddrMode4:
case ARMII::AddrMode6:
// Addressing modes 4 & 6 (load/store) instructions can't encode an
// immediate offset for stack references.
return 0;
default:
break;
}
break; // At most one FI per instruction
}
}
}
return Limit;
}
// In functions that realign the stack, it can be an advantage to spill the
// callee-saved vector registers after realigning the stack. The vst1 and vld1
// instructions take alignment hints that can improve performance.
//
static void checkNumAlignedDPRCS2Regs(MachineFunction &MF) {
MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(0);
if (!SpillAlignedNEONRegs)
return;
// Naked functions don't spill callee-saved registers.
if (MF.getFunction()->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
Attribute::Naked))
return;
// We are planning to use NEON instructions vst1 / vld1.
if (!MF.getTarget().getSubtarget<ARMSubtarget>().hasNEON())
return;
// Don't bother if the default stack alignment is sufficiently high.
if (MF.getTarget().getFrameLowering()->getStackAlignment() >= 8)
return;
// Aligned spills require stack realignment.
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
if (!RegInfo->canRealignStack(MF))
return;
// We always spill contiguous d-registers starting from d8. Count how many
// needs spilling. The register allocator will almost always use the
// callee-saved registers in order, but it can happen that there are holes in
// the range. Registers above the hole will be spilled to the standard DPRCS
// area.
MachineRegisterInfo &MRI = MF.getRegInfo();
unsigned NumSpills = 0;
for (; NumSpills < 8; ++NumSpills)
if (!MRI.isPhysRegUsed(ARM::D8 + NumSpills))
break;
// Don't do this for just one d-register. It's not worth it.
if (NumSpills < 2)
return;
// Spill the first NumSpills D-registers after realigning the stack.
MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(NumSpills);
// A scratch register is required for the vst1 / vld1 instructions.
MF.getRegInfo().setPhysRegUsed(ARM::R4);
}
void
ARMFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
RegScavenger *RS) const {
// This tells PEI to spill the FP as if it is any other callee-save register
// to take advantage the eliminateFrameIndex machinery. This also ensures it
// is spilled in the order specified by getCalleeSavedRegs() to make it easier
// to combine multiple loads / stores.
bool CanEliminateFrame = true;
bool CS1Spilled = false;
bool LRSpilled = false;
unsigned NumGPRSpills = 0;
SmallVector<unsigned, 4> UnspilledCS1GPRs;
SmallVector<unsigned, 4> UnspilledCS2GPRs;
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
MachineFrameInfo *MFI = MF.getFrameInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
// Spill R4 if Thumb2 function requires stack realignment - it will be used as
// scratch register. Also spill R4 if Thumb2 function has varsized objects,
// since it's not always possible to restore sp from fp in a single
// instruction.
// FIXME: It will be better just to find spare register here.
if (AFI->isThumb2Function() &&
(MFI->hasVarSizedObjects() || RegInfo->needsStackRealignment(MF)))
MRI.setPhysRegUsed(ARM::R4);
if (AFI->isThumb1OnlyFunction()) {
// Spill LR if Thumb1 function uses variable length argument lists.
if (AFI->getArgRegsSaveSize() > 0)
MRI.setPhysRegUsed(ARM::LR);
// Spill R4 if Thumb1 epilogue has to restore SP from FP. We don't know
// for sure what the stack size will be, but for this, an estimate is good
// enough. If there anything changes it, it'll be a spill, which implies
// we've used all the registers and so R4 is already used, so not marking
// it here will be OK.
// FIXME: It will be better just to find spare register here.
unsigned StackSize = MFI->estimateStackSize(MF);
if (MFI->hasVarSizedObjects() || StackSize > 508)
MRI.setPhysRegUsed(ARM::R4);
}
// See if we can spill vector registers to aligned stack.
checkNumAlignedDPRCS2Regs(MF);
// Spill the BasePtr if it's used.
if (RegInfo->hasBasePointer(MF))
MRI.setPhysRegUsed(RegInfo->getBaseRegister());
// Don't spill FP if the frame can be eliminated. This is determined
// by scanning the callee-save registers to see if any is used.
const uint16_t *CSRegs = RegInfo->getCalleeSavedRegs();
for (unsigned i = 0; CSRegs[i]; ++i) {
unsigned Reg = CSRegs[i];
bool Spilled = false;
if (MRI.isPhysRegUsed(Reg)) {
Spilled = true;
CanEliminateFrame = false;
}
if (!ARM::GPRRegClass.contains(Reg))
continue;
if (Spilled) {
NumGPRSpills++;
if (!STI.isTargetIOS()) {
if (Reg == ARM::LR)
LRSpilled = true;
CS1Spilled = true;
continue;
}
// Keep track if LR and any of R4, R5, R6, and R7 is spilled.
switch (Reg) {
case ARM::LR:
LRSpilled = true;
// Fallthrough
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
CS1Spilled = true;
break;
default:
break;
}
} else {
if (!STI.isTargetIOS()) {
UnspilledCS1GPRs.push_back(Reg);
continue;
}
switch (Reg) {
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
case ARM::LR:
UnspilledCS1GPRs.push_back(Reg);
break;
default:
UnspilledCS2GPRs.push_back(Reg);
break;
}
}
}
bool ForceLRSpill = false;
if (!LRSpilled && AFI->isThumb1OnlyFunction()) {
unsigned FnSize = GetFunctionSizeInBytes(MF, TII);
// Force LR to be spilled if the Thumb function size is > 2048. This enables
// use of BL to implement far jump. If it turns out that it's not needed
// then the branch fix up path will undo it.
if (FnSize >= (1 << 11)) {
CanEliminateFrame = false;
ForceLRSpill = true;
}
}
// If any of the stack slot references may be out of range of an immediate
// offset, make sure a register (or a spill slot) is available for the
// register scavenger. Note that if we're indexing off the frame pointer, the
// effective stack size is 4 bytes larger since the FP points to the stack
// slot of the previous FP. Also, if we have variable sized objects in the
// function, stack slot references will often be negative, and some of
// our instructions are positive-offset only, so conservatively consider
// that case to want a spill slot (or register) as well. Similarly, if
// the function adjusts the stack pointer during execution and the
// adjustments aren't already part of our stack size estimate, our offset
// calculations may be off, so be conservative.
// FIXME: We could add logic to be more precise about negative offsets
// and which instructions will need a scratch register for them. Is it
// worth the effort and added fragility?
bool BigStack =
(RS &&
(MFI->estimateStackSize(MF) +
((hasFP(MF) && AFI->hasStackFrame()) ? 4:0) >=
estimateRSStackSizeLimit(MF, this)))
|| MFI->hasVarSizedObjects()
|| (MFI->adjustsStack() && !canSimplifyCallFramePseudos(MF));
bool ExtraCSSpill = false;
if (BigStack || !CanEliminateFrame || RegInfo->cannotEliminateFrame(MF)) {
AFI->setHasStackFrame(true);
// If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled.
// Spill LR as well so we can fold BX_RET to the registers restore (LDM).
if (!LRSpilled && CS1Spilled) {
MRI.setPhysRegUsed(ARM::LR);
NumGPRSpills++;
UnspilledCS1GPRs.erase(std::find(UnspilledCS1GPRs.begin(),
UnspilledCS1GPRs.end(), (unsigned)ARM::LR));
ForceLRSpill = false;
ExtraCSSpill = true;
}
if (hasFP(MF)) {
MRI.setPhysRegUsed(FramePtr);
NumGPRSpills++;
}
// If stack and double are 8-byte aligned and we are spilling an odd number
// of GPRs, spill one extra callee save GPR so we won't have to pad between
// the integer and double callee save areas.
unsigned TargetAlign = getStackAlignment();
if (TargetAlign == 8 && (NumGPRSpills & 1)) {
if (CS1Spilled && !UnspilledCS1GPRs.empty()) {
for (unsigned i = 0, e = UnspilledCS1GPRs.size(); i != e; ++i) {
unsigned Reg = UnspilledCS1GPRs[i];
// Don't spill high register if the function is thumb1
if (!AFI->isThumb1OnlyFunction() ||
isARMLowRegister(Reg) || Reg == ARM::LR) {
MRI.setPhysRegUsed(Reg);
if (!MRI.isReserved(Reg))
ExtraCSSpill = true;
break;
}
}
} else if (!UnspilledCS2GPRs.empty() && !AFI->isThumb1OnlyFunction()) {
unsigned Reg = UnspilledCS2GPRs.front();
MRI.setPhysRegUsed(Reg);
if (!MRI.isReserved(Reg))
ExtraCSSpill = true;
}
}
// Estimate if we might need to scavenge a register at some point in order
// to materialize a stack offset. If so, either spill one additional
// callee-saved register or reserve a special spill slot to facilitate
// register scavenging. Thumb1 needs a spill slot for stack pointer
// adjustments also, even when the frame itself is small.
if (BigStack && !ExtraCSSpill) {
// If any non-reserved CS register isn't spilled, just spill one or two
// extra. That should take care of it!
unsigned NumExtras = TargetAlign / 4;
SmallVector<unsigned, 2> Extras;
while (NumExtras && !UnspilledCS1GPRs.empty()) {
unsigned Reg = UnspilledCS1GPRs.back();
UnspilledCS1GPRs.pop_back();
if (!MRI.isReserved(Reg) &&
(!AFI->isThumb1OnlyFunction() || isARMLowRegister(Reg) ||
Reg == ARM::LR)) {
Extras.push_back(Reg);
NumExtras--;
}
}
// For non-Thumb1 functions, also check for hi-reg CS registers
if (!AFI->isThumb1OnlyFunction()) {
while (NumExtras && !UnspilledCS2GPRs.empty()) {
unsigned Reg = UnspilledCS2GPRs.back();
UnspilledCS2GPRs.pop_back();
if (!MRI.isReserved(Reg)) {
Extras.push_back(Reg);
NumExtras--;
}
}
}
if (Extras.size() && NumExtras == 0) {
for (unsigned i = 0, e = Extras.size(); i != e; ++i) {
MRI.setPhysRegUsed(Extras[i]);
}
} else if (!AFI->isThumb1OnlyFunction()) {
// note: Thumb1 functions spill to R12, not the stack. Reserve a slot
// closest to SP or frame pointer.
const TargetRegisterClass *RC = &ARM::GPRRegClass;
RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
}
}
}
if (ForceLRSpill) {
MRI.setPhysRegUsed(ARM::LR);
AFI->setLRIsSpilledForFarJump(true);
}
}
void ARMFrameLowering::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
if (!hasReservedCallFrame(MF)) {
// If we have alloca, convert as follows:
// ADJCALLSTACKDOWN -> sub, sp, sp, amount
// ADJCALLSTACKUP -> add, sp, sp, amount
MachineInstr *Old = I;
DebugLoc dl = Old->getDebugLoc();
unsigned Amount = Old->getOperand(0).getImm();
if (Amount != 0) {
// We need to keep the stack aligned properly. To do this, we round the
// amount of space needed for the outgoing arguments up to the next
// alignment boundary.
unsigned Align = getStackAlignment();
Amount = (Amount+Align-1)/Align*Align;
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
assert(!AFI->isThumb1OnlyFunction() &&
"This eliminateCallFramePseudoInstr does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
// Replace the pseudo instruction with a new instruction...
unsigned Opc = Old->getOpcode();
int PIdx = Old->findFirstPredOperandIdx();
ARMCC::CondCodes Pred = (PIdx == -1)
? ARMCC::AL : (ARMCC::CondCodes)Old->getOperand(PIdx).getImm();
if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) {
// Note: PredReg is operand 2 for ADJCALLSTACKDOWN.
unsigned PredReg = Old->getOperand(2).getReg();
emitSPUpdate(isARM, MBB, I, dl, TII, -Amount, MachineInstr::NoFlags,
Pred, PredReg);
} else {
// Note: PredReg is operand 3 for ADJCALLSTACKUP.
unsigned PredReg = Old->getOperand(3).getReg();
assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP);
emitSPUpdate(isARM, MBB, I, dl, TII, Amount, MachineInstr::NoFlags,
Pred, PredReg);
}
}
}
MBB.erase(I);
}
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