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llvm-project/llvm/lib/Target/Hexagon/HexagonFrameLowering.cpp

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//===-- HexagonFrameLowering.cpp - Define frame lowering ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "hexagon-pei"
#include "HexagonFrameLowering.h"
#include "Hexagon.h"
#include "HexagonInstrInfo.h"
#include "HexagonMachineFunctionInfo.h"
#include "HexagonRegisterInfo.h"
#include "HexagonSubtarget.h"
#include "HexagonTargetMachine.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachinePostDominators.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
// Hexagon stack frame layout as defined by the ABI:
//
// Incoming arguments
// passed via stack
// |
// |
// SP during function's FP during function's |
// +-- runtime (top of stack) runtime (bottom) --+ |
// | | |
// --++---------------------+------------------+-----------------++-+-------
// | parameter area for | variable-size | fixed-size |LR| arg
// | called functions | local objects | local objects |FP|
// --+----------------------+------------------+-----------------+--+-------
// <- size known -> <- size unknown -> <- size known ->
//
// Low address High address
//
// <--- stack growth
//
//
// - In any circumstances, the outgoing function arguments are always accessi-
// ble using the SP, and the incoming arguments are accessible using the FP.
// - If the local objects are not aligned, they can always be accessed using
// the FP.
// - If there are no variable-sized objects, the local objects can always be
// accessed using the SP, regardless whether they are aligned or not. (The
// alignment padding will be at the bottom of the stack (highest address),
// and so the offset with respect to the SP will be known at the compile-
// -time.)
//
// The only complication occurs if there are both, local aligned objects, and
// dynamically allocated (variable-sized) objects. The alignment pad will be
// placed between the FP and the local objects, thus preventing the use of the
// FP to access the local objects. At the same time, the variable-sized objects
// will be between the SP and the local objects, thus introducing an unknown
// distance from the SP to the locals.
//
// To avoid this problem, a new register is created that holds the aligned
// address of the bottom of the stack, referred in the sources as AP (aligned
// pointer). The AP will be equal to "FP-p", where "p" is the smallest pad
// that aligns AP to the required boundary (a maximum of the alignments of
// all stack objects, fixed- and variable-sized). All local objects[1] will
// then use AP as the base pointer.
// [1] The exception is with "fixed" stack objects. "Fixed" stack objects get
// their name from being allocated at fixed locations on the stack, relative
// to the FP. In the presence of dynamic allocation and local alignment, such
// objects can only be accessed through the FP.
//
// Illustration of the AP:
// FP --+
// |
// ---------------+---------------------+-----+-----------------------++-+--
// Rest of the | Local stack objects | Pad | Fixed stack objects |LR|
// stack frame | (aligned) | | (CSR, spills, etc.) |FP|
// ---------------+---------------------+-----+-----------------+-----+--+--
// |<-- Multiple of the -->|
// stack alignment +-- AP
//
// The AP is set up at the beginning of the function. Since it is not a dedi-
// cated (reserved) register, it needs to be kept live throughout the function
// to be available as the base register for local object accesses.
// Normally, an address of a stack objects is obtained by a pseudo-instruction
// TFR_FI. To access local objects with the AP register present, a different
// pseudo-instruction needs to be used: TFR_FIA. The TFR_FIA takes one extra
// argument compared to TFR_FI: the first input register is the AP register.
// This keeps the register live between its definition and its uses.
// The AP register is originally set up using pseudo-instruction ALIGNA:
// AP = ALIGNA A
// where
// A - required stack alignment
// The alignment value must be the maximum of all alignments required by
// any stack object.
// The dynamic allocation uses a pseudo-instruction ALLOCA:
// Rd = ALLOCA Rs, A
// where
// Rd - address of the allocated space
// Rs - minimum size (the actual allocated can be larger to accommodate
// alignment)
// A - required alignment
using namespace llvm;
static cl::opt<bool> DisableDeallocRet("disable-hexagon-dealloc-ret",
cl::Hidden, cl::desc("Disable Dealloc Return for Hexagon target"));
static cl::opt<int> NumberScavengerSlots("number-scavenger-slots",
cl::Hidden, cl::desc("Set the number of scavenger slots"), cl::init(2),
cl::ZeroOrMore);
static cl::opt<int> SpillFuncThreshold("spill-func-threshold",
cl::Hidden, cl::desc("Specify O2(not Os) spill func threshold"),
cl::init(6), cl::ZeroOrMore);
static cl::opt<int> SpillFuncThresholdOs("spill-func-threshold-Os",
cl::Hidden, cl::desc("Specify Os spill func threshold"),
cl::init(1), cl::ZeroOrMore);
static cl::opt<bool> EnableShrinkWrapping("hexagon-shrink-frame",
cl::init(true), cl::Hidden, cl::ZeroOrMore,
cl::desc("Enable stack frame shrink wrapping"));
static cl::opt<unsigned> ShrinkLimit("shrink-frame-limit", cl::init(UINT_MAX),
cl::Hidden, cl::ZeroOrMore, cl::desc("Max count of stack frame "
"shrink-wraps"));
static cl::opt<bool> UseAllocframe("use-allocframe", cl::init(true),
cl::Hidden, cl::desc("Use allocframe more conservatively"));
namespace llvm {
void initializeHexagonCallFrameInformationPass(PassRegistry&);
FunctionPass *createHexagonCallFrameInformation();
}
namespace {
class HexagonCallFrameInformation : public MachineFunctionPass {
public:
static char ID;
HexagonCallFrameInformation() : MachineFunctionPass(ID) {
PassRegistry &PR = *PassRegistry::getPassRegistry();
initializeHexagonCallFrameInformationPass(PR);
}
bool runOnMachineFunction(MachineFunction &MF) override;
};
char HexagonCallFrameInformation::ID = 0;
}
bool HexagonCallFrameInformation::runOnMachineFunction(MachineFunction &MF) {
auto &HFI = *MF.getSubtarget<HexagonSubtarget>().getFrameLowering();
bool NeedCFI = MF.getMMI().hasDebugInfo() ||
MF.getFunction()->needsUnwindTableEntry();
if (!NeedCFI)
return false;
HFI.insertCFIInstructions(MF);
return true;
}
INITIALIZE_PASS(HexagonCallFrameInformation, "hexagon-cfi",
"Hexagon call frame information", false, false)
FunctionPass *llvm::createHexagonCallFrameInformation() {
return new HexagonCallFrameInformation();
}
namespace {
/// Map a register pair Reg to the subregister that has the greater "number",
/// i.e. D3 (aka R7:6) will be mapped to R7, etc.
unsigned getMax32BitSubRegister(unsigned Reg, const TargetRegisterInfo &TRI,
bool hireg = true) {
if (Reg < Hexagon::D0 || Reg > Hexagon::D15)
return Reg;
unsigned RegNo = 0;
for (MCSubRegIterator SubRegs(Reg, &TRI); SubRegs.isValid(); ++SubRegs) {
if (hireg) {
if (*SubRegs > RegNo)
RegNo = *SubRegs;
} else {
if (!RegNo || *SubRegs < RegNo)
RegNo = *SubRegs;
}
}
return RegNo;
}
/// Returns the callee saved register with the largest id in the vector.
unsigned getMaxCalleeSavedReg(const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo &TRI) {
assert(Hexagon::R1 > 0 &&
"Assume physical registers are encoded as positive integers");
if (CSI.empty())
return 0;
unsigned Max = getMax32BitSubRegister(CSI[0].getReg(), TRI);
for (unsigned I = 1, E = CSI.size(); I < E; ++I) {
unsigned Reg = getMax32BitSubRegister(CSI[I].getReg(), TRI);
if (Reg > Max)
Max = Reg;
}
return Max;
}
/// Checks if the basic block contains any instruction that needs a stack
/// frame to be already in place.
bool needsStackFrame(const MachineBasicBlock &MBB, const BitVector &CSR) {
for (auto &I : MBB) {
const MachineInstr *MI = &I;
if (MI->isCall())
return true;
unsigned Opc = MI->getOpcode();
switch (Opc) {
case Hexagon::ALLOCA:
case Hexagon::ALIGNA:
return true;
default:
break;
}
// Check individual operands.
for (const MachineOperand &MO : MI->operands()) {
// While the presence of a frame index does not prove that a stack
// frame will be required, all frame indexes should be within alloc-
// frame/deallocframe. Otherwise, the code that translates a frame
// index into an offset would have to be aware of the placement of
// the frame creation/destruction instructions.
if (MO.isFI())
return true;
if (!MO.isReg())
continue;
unsigned R = MO.getReg();
// Virtual registers will need scavenging, which then may require
// a stack slot.
if (TargetRegisterInfo::isVirtualRegister(R))
return true;
if (CSR[R])
return true;
}
}
return false;
}
/// Returns true if MBB has a machine instructions that indicates a tail call
/// in the block.
bool hasTailCall(const MachineBasicBlock &MBB) {
MachineBasicBlock::const_iterator I = MBB.getLastNonDebugInstr();
unsigned RetOpc = I->getOpcode();
return RetOpc == Hexagon::TCRETURNi || RetOpc == Hexagon::TCRETURNr;
}
/// Returns true if MBB contains an instruction that returns.
bool hasReturn(const MachineBasicBlock &MBB) {
for (auto I = MBB.getFirstTerminator(), E = MBB.end(); I != E; ++I)
if (I->isReturn())
return true;
return false;
}
}
/// Implements shrink-wrapping of the stack frame. By default, stack frame
/// is created in the function entry block, and is cleaned up in every block
/// that returns. This function finds alternate blocks: one for the frame
/// setup (prolog) and one for the cleanup (epilog).
void HexagonFrameLowering::findShrunkPrologEpilog(MachineFunction &MF,
MachineBasicBlock *&PrologB, MachineBasicBlock *&EpilogB) const {
static unsigned ShrinkCounter = 0;
if (ShrinkLimit.getPosition()) {
if (ShrinkCounter >= ShrinkLimit)
return;
ShrinkCounter++;
}
auto &HST = static_cast<const HexagonSubtarget&>(MF.getSubtarget());
auto &HRI = *HST.getRegisterInfo();
MachineDominatorTree MDT;
MDT.runOnMachineFunction(MF);
MachinePostDominatorTree MPT;
MPT.runOnMachineFunction(MF);
typedef DenseMap<unsigned,unsigned> UnsignedMap;
UnsignedMap RPO;
typedef ReversePostOrderTraversal<const MachineFunction*> RPOTType;
RPOTType RPOT(&MF);
unsigned RPON = 0;
for (RPOTType::rpo_iterator I = RPOT.begin(), E = RPOT.end(); I != E; ++I)
RPO[(*I)->getNumber()] = RPON++;
// Don't process functions that have loops, at least for now. Placement
// of prolog and epilog must take loop structure into account. For simpli-
// city don't do it right now.
for (auto &I : MF) {
unsigned BN = RPO[I.getNumber()];
for (auto SI = I.succ_begin(), SE = I.succ_end(); SI != SE; ++SI) {
// If found a back-edge, return.
if (RPO[(*SI)->getNumber()] <= BN)
return;
}
}
// Collect the set of blocks that need a stack frame to execute. Scan
// each block for uses/defs of callee-saved registers, calls, etc.
SmallVector<MachineBasicBlock*,16> SFBlocks;
BitVector CSR(Hexagon::NUM_TARGET_REGS);
for (const MCPhysReg *P = HRI.getCalleeSavedRegs(&MF); *P; ++P)
CSR[*P] = true;
for (auto &I : MF)
if (needsStackFrame(I, CSR))
SFBlocks.push_back(&I);
DEBUG({
dbgs() << "Blocks needing SF: {";
for (auto &B : SFBlocks)
dbgs() << " BB#" << B->getNumber();
dbgs() << " }\n";
});
// No frame needed?
if (SFBlocks.empty())
return;
// Pick a common dominator and a common post-dominator.
MachineBasicBlock *DomB = SFBlocks[0];
for (unsigned i = 1, n = SFBlocks.size(); i < n; ++i) {
DomB = MDT.findNearestCommonDominator(DomB, SFBlocks[i]);
if (!DomB)
break;
}
MachineBasicBlock *PDomB = SFBlocks[0];
for (unsigned i = 1, n = SFBlocks.size(); i < n; ++i) {
PDomB = MPT.findNearestCommonDominator(PDomB, SFBlocks[i]);
if (!PDomB)
break;
}
DEBUG({
dbgs() << "Computed dom block: BB#";
if (DomB) dbgs() << DomB->getNumber();
else dbgs() << "<null>";
dbgs() << ", computed pdom block: BB#";
if (PDomB) dbgs() << PDomB->getNumber();
else dbgs() << "<null>";
dbgs() << "\n";
});
if (!DomB || !PDomB)
return;
// Make sure that DomB dominates PDomB and PDomB post-dominates DomB.
if (!MDT.dominates(DomB, PDomB)) {
DEBUG(dbgs() << "Dom block does not dominate pdom block\n");
return;
}
if (!MPT.dominates(PDomB, DomB)) {
DEBUG(dbgs() << "PDom block does not post-dominate dom block\n");
return;
}
// Finally, everything seems right.
PrologB = DomB;
EpilogB = PDomB;
}
/// Perform most of the PEI work here:
/// - saving/restoring of the callee-saved registers,
/// - stack frame creation and destruction.
/// Normally, this work is distributed among various functions, but doing it
/// in one place allows shrink-wrapping of the stack frame.
void HexagonFrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
auto &HST = static_cast<const HexagonSubtarget&>(MF.getSubtarget());
auto &HRI = *HST.getRegisterInfo();
assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
MachineFrameInfo *MFI = MF.getFrameInfo();
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
MachineBasicBlock *PrologB = &MF.front(), *EpilogB = nullptr;
if (EnableShrinkWrapping)
findShrunkPrologEpilog(MF, PrologB, EpilogB);
insertCSRSpillsInBlock(*PrologB, CSI, HRI);
insertPrologueInBlock(*PrologB);
if (EpilogB) {
insertCSRRestoresInBlock(*EpilogB, CSI, HRI);
insertEpilogueInBlock(*EpilogB);
} else {
for (auto &B : MF)
if (B.isReturnBlock())
insertCSRRestoresInBlock(B, CSI, HRI);
for (auto &B : MF)
if (B.isReturnBlock())
insertEpilogueInBlock(B);
}
}
void HexagonFrameLowering::insertPrologueInBlock(MachineBasicBlock &MBB) const {
MachineFunction &MF = *MBB.getParent();
MachineFrameInfo *MFI = MF.getFrameInfo();
auto &HST = MF.getSubtarget<HexagonSubtarget>();
auto &HII = *HST.getInstrInfo();
auto &HRI = *HST.getRegisterInfo();
DebugLoc dl;
unsigned MaxAlign = std::max(MFI->getMaxAlignment(), getStackAlignment());
// Calculate the total stack frame size.
// Get the number of bytes to allocate from the FrameInfo.
unsigned FrameSize = MFI->getStackSize();
// Round up the max call frame size to the max alignment on the stack.
unsigned MaxCFA = RoundUpToAlignment(MFI->getMaxCallFrameSize(), MaxAlign);
MFI->setMaxCallFrameSize(MaxCFA);
FrameSize = MaxCFA + RoundUpToAlignment(FrameSize, MaxAlign);
MFI->setStackSize(FrameSize);
bool AlignStack = (MaxAlign > getStackAlignment());
// Get the number of bytes to allocate from the FrameInfo.
unsigned NumBytes = MFI->getStackSize();
unsigned SP = HRI.getStackRegister();
unsigned MaxCF = MFI->getMaxCallFrameSize();
MachineBasicBlock::iterator InsertPt = MBB.begin();
auto *FuncInfo = MF.getInfo<HexagonMachineFunctionInfo>();
auto &AdjustRegs = FuncInfo->getAllocaAdjustInsts();
for (auto MI : AdjustRegs) {
assert((MI->getOpcode() == Hexagon::ALLOCA) && "Expected alloca");
expandAlloca(MI, HII, SP, MaxCF);
MI->eraseFromParent();
}
if (!hasFP(MF))
return;
// Check for overflow.
// Hexagon_TODO: Ugh! hardcoding. Is there an API that can be used?
const unsigned int ALLOCFRAME_MAX = 16384;
// Create a dummy memory operand to avoid allocframe from being treated as
// a volatile memory reference.
MachineMemOperand *MMO =
MF.getMachineMemOperand(MachinePointerInfo(), MachineMemOperand::MOStore,
4, 4);
if (NumBytes >= ALLOCFRAME_MAX) {
// Emit allocframe(#0).
BuildMI(MBB, InsertPt, dl, HII.get(Hexagon::S2_allocframe))
.addImm(0)
.addMemOperand(MMO);
// Subtract offset from frame pointer.
// We use a caller-saved non-parameter register for that.
unsigned CallerSavedReg = HRI.getFirstCallerSavedNonParamReg();
BuildMI(MBB, InsertPt, dl, HII.get(Hexagon::CONST32_Int_Real),
CallerSavedReg).addImm(NumBytes);
BuildMI(MBB, InsertPt, dl, HII.get(Hexagon::A2_sub), SP)
.addReg(SP)
.addReg(CallerSavedReg);
} else {
BuildMI(MBB, InsertPt, dl, HII.get(Hexagon::S2_allocframe))
.addImm(NumBytes)
.addMemOperand(MMO);
}
if (AlignStack) {
BuildMI(MBB, InsertPt, dl, HII.get(Hexagon::A2_andir), SP)
.addReg(SP)
.addImm(-int64_t(MaxAlign));
}
}
void HexagonFrameLowering::insertEpilogueInBlock(MachineBasicBlock &MBB) const {
MachineFunction &MF = *MBB.getParent();
if (!hasFP(MF))
return;
auto &HST = static_cast<const HexagonSubtarget&>(MF.getSubtarget());
auto &HII = *HST.getInstrInfo();
auto &HRI = *HST.getRegisterInfo();
unsigned SP = HRI.getStackRegister();
MachineInstr *RetI = nullptr;
for (auto &I : MBB) {
if (!I.isReturn())
continue;
RetI = &I;
break;
}
unsigned RetOpc = RetI ? RetI->getOpcode() : 0;
MachineBasicBlock::iterator InsertPt = MBB.getFirstTerminator();
DebugLoc DL;
if (InsertPt != MBB.end())
DL = InsertPt->getDebugLoc();
else if (!MBB.empty())
DL = std::prev(MBB.end())->getDebugLoc();
// Handle EH_RETURN.
if (RetOpc == Hexagon::EH_RETURN_JMPR) {
BuildMI(MBB, InsertPt, DL, HII.get(Hexagon::L2_deallocframe));
BuildMI(MBB, InsertPt, DL, HII.get(Hexagon::A2_add), SP)
.addReg(SP)
.addReg(Hexagon::R28);
return;
}
// Check for RESTORE_DEALLOC_RET* tail call. Don't emit an extra dealloc-
// frame instruction if we encounter it.
if (RetOpc == Hexagon::RESTORE_DEALLOC_RET_JMP_V4) {
MachineBasicBlock::iterator It = RetI;
++It;
// Delete all instructions after the RESTORE (except labels).
while (It != MBB.end()) {
if (!It->isLabel())
It = MBB.erase(It);
else
++It;
}
return;
}
// It is possible that the restoring code is a call to a library function.
// All of the restore* functions include "deallocframe", so we need to make
// sure that we don't add an extra one.
bool NeedsDeallocframe = true;
if (!MBB.empty() && InsertPt != MBB.begin()) {
MachineBasicBlock::iterator PrevIt = std::prev(InsertPt);
unsigned COpc = PrevIt->getOpcode();
if (COpc == Hexagon::RESTORE_DEALLOC_BEFORE_TAILCALL_V4)
NeedsDeallocframe = false;
}
if (!NeedsDeallocframe)
return;
// If the returning instruction is JMPret, replace it with dealloc_return,
// otherwise just add deallocframe. The function could be returning via a
// tail call.
if (RetOpc != Hexagon::JMPret || DisableDeallocRet) {
BuildMI(MBB, InsertPt, DL, HII.get(Hexagon::L2_deallocframe));
return;
}
unsigned NewOpc = Hexagon::L4_return;
MachineInstr *NewI = BuildMI(MBB, RetI, DL, HII.get(NewOpc));
// Transfer the function live-out registers.
NewI->copyImplicitOps(MF, RetI);
MBB.erase(RetI);
}
namespace {
bool IsAllocFrame(MachineBasicBlock::const_iterator It) {
if (!It->isBundle())
return It->getOpcode() == Hexagon::S2_allocframe;
auto End = It->getParent()->instr_end();
MachineBasicBlock::const_instr_iterator I = It.getInstrIterator();
while (++I != End && I->isBundled())
if (I->getOpcode() == Hexagon::S2_allocframe)
return true;
return false;
}
MachineBasicBlock::iterator FindAllocFrame(MachineBasicBlock &B) {
for (auto &I : B)
if (IsAllocFrame(I))
return I;
return B.end();
}
}
void HexagonFrameLowering::insertCFIInstructions(MachineFunction &MF) const {
for (auto &B : MF) {
auto AF = FindAllocFrame(B);
if (AF == B.end())
continue;
insertCFIInstructionsAt(B, ++AF);
}
}
void HexagonFrameLowering::insertCFIInstructionsAt(MachineBasicBlock &MBB,
MachineBasicBlock::iterator At) const {
MachineFunction &MF = *MBB.getParent();
MachineFrameInfo *MFI = MF.getFrameInfo();
MachineModuleInfo &MMI = MF.getMMI();
auto &HST = MF.getSubtarget<HexagonSubtarget>();
auto &HII = *HST.getInstrInfo();
auto &HRI = *HST.getRegisterInfo();
// If CFI instructions have debug information attached, something goes
// wrong with the final assembly generation: the prolog_end is placed
// in a wrong location.
DebugLoc DL;
const MCInstrDesc &CFID = HII.get(TargetOpcode::CFI_INSTRUCTION);
MCSymbol *FrameLabel = MMI.getContext().createTempSymbol();
if (hasFP(MF)) {
unsigned DwFPReg = HRI.getDwarfRegNum(HRI.getFrameRegister(), true);
unsigned DwRAReg = HRI.getDwarfRegNum(HRI.getRARegister(), true);
// Define CFA via an offset from the value of FP.
//
// -8 -4 0 (SP)
// --+----+----+---------------------
// | FP | LR | increasing addresses -->
// --+----+----+---------------------
// | +-- Old SP (before allocframe)
// +-- New FP (after allocframe)
//
// MCCFIInstruction::createDefCfa subtracts the offset from the register.
// MCCFIInstruction::createOffset takes the offset without sign change.
auto DefCfa = MCCFIInstruction::createDefCfa(FrameLabel, DwFPReg, -8);
BuildMI(MBB, At, DL, CFID)
.addCFIIndex(MMI.addFrameInst(DefCfa));
// R31 (return addr) = CFA - 4
auto OffR31 = MCCFIInstruction::createOffset(FrameLabel, DwRAReg, -4);
BuildMI(MBB, At, DL, CFID)
.addCFIIndex(MMI.addFrameInst(OffR31));
// R30 (frame ptr) = CFA - 8
auto OffR30 = MCCFIInstruction::createOffset(FrameLabel, DwFPReg, -8);
BuildMI(MBB, At, DL, CFID)
.addCFIIndex(MMI.addFrameInst(OffR30));
}
static unsigned int RegsToMove[] = {
Hexagon::R1, Hexagon::R0, Hexagon::R3, Hexagon::R2,
Hexagon::R17, Hexagon::R16, Hexagon::R19, Hexagon::R18,
Hexagon::R21, Hexagon::R20, Hexagon::R23, Hexagon::R22,
Hexagon::R25, Hexagon::R24, Hexagon::R27, Hexagon::R26,
Hexagon::D0, Hexagon::D1, Hexagon::D8, Hexagon::D9,
Hexagon::D10, Hexagon::D11, Hexagon::D12, Hexagon::D13,
Hexagon::NoRegister
};
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
for (unsigned i = 0; RegsToMove[i] != Hexagon::NoRegister; ++i) {
unsigned Reg = RegsToMove[i];
auto IfR = [Reg] (const CalleeSavedInfo &C) -> bool {
return C.getReg() == Reg;
};
auto F = std::find_if(CSI.begin(), CSI.end(), IfR);
if (F == CSI.end())
continue;
// Subtract 8 to make room for R30 and R31, which are added above.
unsigned FrameReg;
int64_t Offset = getFrameIndexReference(MF, F->getFrameIdx(), FrameReg) - 8;
if (Reg < Hexagon::D0 || Reg > Hexagon::D15) {
unsigned DwarfReg = HRI.getDwarfRegNum(Reg, true);
auto OffReg = MCCFIInstruction::createOffset(FrameLabel, DwarfReg,
Offset);
BuildMI(MBB, At, DL, CFID)
.addCFIIndex(MMI.addFrameInst(OffReg));
} else {
// Split the double regs into subregs, and generate appropriate
// cfi_offsets.
// The only reason, we are split double regs is, llvm-mc does not
// understand paired registers for cfi_offset.
// Eg .cfi_offset r1:0, -64
unsigned HiReg = HRI.getSubReg(Reg, Hexagon::subreg_hireg);
unsigned LoReg = HRI.getSubReg(Reg, Hexagon::subreg_loreg);
unsigned HiDwarfReg = HRI.getDwarfRegNum(HiReg, true);
unsigned LoDwarfReg = HRI.getDwarfRegNum(LoReg, true);
auto OffHi = MCCFIInstruction::createOffset(FrameLabel, HiDwarfReg,
Offset+4);
BuildMI(MBB, At, DL, CFID)
.addCFIIndex(MMI.addFrameInst(OffHi));
auto OffLo = MCCFIInstruction::createOffset(FrameLabel, LoDwarfReg,
Offset);
BuildMI(MBB, At, DL, CFID)
.addCFIIndex(MMI.addFrameInst(OffLo));
}
}
}
bool HexagonFrameLowering::hasFP(const MachineFunction &MF) const {
auto &MFI = *MF.getFrameInfo();
auto &HRI = *MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
bool HasFixed = MFI.getNumFixedObjects();
bool HasPrealloc = const_cast<MachineFrameInfo&>(MFI)
.getLocalFrameObjectCount();
bool HasExtraAlign = HRI.needsStackRealignment(MF);
bool HasAlloca = MFI.hasVarSizedObjects();
// Insert ALLOCFRAME if we need to or at -O0 for the debugger. Think
// that this shouldn't be required, but doing so now because gcc does and
// gdb can't break at the start of the function without it. Will remove if
// this turns out to be a gdb bug.
//
if (MF.getTarget().getOptLevel() == CodeGenOpt::None)
return true;
// By default we want to use SP (since it's always there). FP requires
// some setup (i.e. ALLOCFRAME).
// Fixed and preallocated objects need FP if the distance from them to
// the SP is unknown (as is with alloca or aligna).
if ((HasFixed || HasPrealloc) && (HasAlloca || HasExtraAlign))
return true;
if (MFI.getStackSize() > 0) {
if (UseAllocframe)
return true;
}
if (MFI.hasCalls() ||
MF.getInfo<HexagonMachineFunctionInfo>()->hasClobberLR())
return true;
return false;
}
enum SpillKind {
SK_ToMem,
SK_FromMem,
SK_FromMemTailcall
};
static const char *
getSpillFunctionFor(unsigned MaxReg, SpillKind SpillType) {
const char * V4SpillToMemoryFunctions[] = {
"__save_r16_through_r17",
"__save_r16_through_r19",
"__save_r16_through_r21",
"__save_r16_through_r23",
"__save_r16_through_r25",
"__save_r16_through_r27" };
const char * V4SpillFromMemoryFunctions[] = {
"__restore_r16_through_r17_and_deallocframe",
"__restore_r16_through_r19_and_deallocframe",
"__restore_r16_through_r21_and_deallocframe",
"__restore_r16_through_r23_and_deallocframe",
"__restore_r16_through_r25_and_deallocframe",
"__restore_r16_through_r27_and_deallocframe" };
const char * V4SpillFromMemoryTailcallFunctions[] = {
"__restore_r16_through_r17_and_deallocframe_before_tailcall",
"__restore_r16_through_r19_and_deallocframe_before_tailcall",
"__restore_r16_through_r21_and_deallocframe_before_tailcall",
"__restore_r16_through_r23_and_deallocframe_before_tailcall",
"__restore_r16_through_r25_and_deallocframe_before_tailcall",
"__restore_r16_through_r27_and_deallocframe_before_tailcall"
};
const char **SpillFunc = nullptr;
switch(SpillType) {
case SK_ToMem:
SpillFunc = V4SpillToMemoryFunctions;
break;
case SK_FromMem:
SpillFunc = V4SpillFromMemoryFunctions;
break;
case SK_FromMemTailcall:
SpillFunc = V4SpillFromMemoryTailcallFunctions;
break;
}
assert(SpillFunc && "Unknown spill kind");
// Spill all callee-saved registers up to the highest register used.
switch (MaxReg) {
case Hexagon::R17:
return SpillFunc[0];
case Hexagon::R19:
return SpillFunc[1];
case Hexagon::R21:
return SpillFunc[2];
case Hexagon::R23:
return SpillFunc[3];
case Hexagon::R25:
return SpillFunc[4];
case Hexagon::R27:
return SpillFunc[5];
default:
llvm_unreachable("Unhandled maximum callee save register");
}
return 0;
}
/// Adds all callee-saved registers up to MaxReg to the instruction.
static void addCalleeSaveRegistersAsImpOperand(MachineInstr *Inst,
unsigned MaxReg, bool IsDef) {
// Add the callee-saved registers as implicit uses.
for (unsigned R = Hexagon::R16; R <= MaxReg; ++R) {
MachineOperand ImpUse = MachineOperand::CreateReg(R, IsDef, true);
Inst->addOperand(ImpUse);
}
}
int HexagonFrameLowering::getFrameIndexReference(const MachineFunction &MF,
int FI, unsigned &FrameReg) const {
auto &MFI = *MF.getFrameInfo();
auto &HRI = *MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
// Large parts of this code are shared with HRI::eliminateFrameIndex.
int Offset = MFI.getObjectOffset(FI);
bool HasAlloca = MFI.hasVarSizedObjects();
bool HasExtraAlign = HRI.needsStackRealignment(MF);
bool NoOpt = MF.getTarget().getOptLevel() == CodeGenOpt::None;
unsigned SP = HRI.getStackRegister(), FP = HRI.getFrameRegister();
unsigned AP = 0;
if (const MachineInstr *AI = getAlignaInstr(MF))
AP = AI->getOperand(0).getReg();
unsigned FrameSize = MFI.getStackSize();
bool UseFP = false, UseAP = false; // Default: use SP (except at -O0).
// Use FP at -O0, except when there are objects with extra alignment.
// That additional alignment requirement may cause a pad to be inserted,
// which will make it impossible to use FP to access objects located
// past the pad.
if (NoOpt && !HasExtraAlign)
UseFP = true;
if (MFI.isFixedObjectIndex(FI) || MFI.isObjectPreAllocated(FI)) {
// Fixed and preallocated objects will be located before any padding
// so FP must be used to access them.
UseFP |= (HasAlloca || HasExtraAlign);
} else {
if (HasAlloca) {
if (HasExtraAlign)
UseAP = true;
else
UseFP = true;
}
}
// If FP was picked, then there had better be FP.
bool HasFP = hasFP(MF);
assert((HasFP || !UseFP) && "This function must have frame pointer");
// Having FP implies allocframe. Allocframe will store extra 8 bytes:
// FP/LR. If the base register is used to access an object across these
// 8 bytes, then the offset will need to be adjusted by 8.
//
// After allocframe:
// HexagonISelLowering adds 8 to ---+
// the offsets of all stack-based |
// arguments (*) |
// |
// getObjectOffset < 0 0 8 getObjectOffset >= 8
// ------------------------+-----+------------------------> increasing
// <local objects> |FP/LR| <input arguments> addresses
// -----------------+------+-----+------------------------>
// | |
// SP/AP point --+ +-- FP points here (**)
// somewhere on
// this side of FP/LR
//
// (*) See LowerFormalArguments. The FP/LR is assumed to be present.
// (**) *FP == old-FP. FP+0..7 are the bytes of FP/LR.
// The lowering assumes that FP/LR is present, and so the offsets of
// the formal arguments start at 8. If FP/LR is not there we need to
// reduce the offset by 8.
if (Offset > 0 && !HasFP)
Offset -= 8;
if (UseFP)
FrameReg = FP;
else if (UseAP)
FrameReg = AP;
else
FrameReg = SP;
// Calculate the actual offset in the instruction. If there is no FP
// (in other words, no allocframe), then SP will not be adjusted (i.e.
// there will be no SP -= FrameSize), so the frame size should not be
// added to the calculated offset.
int RealOffset = Offset;
if (!UseFP && !UseAP && HasFP)
RealOffset = FrameSize+Offset;
return RealOffset;
}
bool HexagonFrameLowering::insertCSRSpillsInBlock(MachineBasicBlock &MBB,
const CSIVect &CSI, const HexagonRegisterInfo &HRI) const {
if (CSI.empty())
return true;
MachineBasicBlock::iterator MI = MBB.begin();
MachineFunction &MF = *MBB.getParent();
auto &HII = *MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
if (useSpillFunction(MF, CSI)) {
unsigned MaxReg = getMaxCalleeSavedReg(CSI, HRI);
const char *SpillFun = getSpillFunctionFor(MaxReg, SK_ToMem);
// Call spill function.
DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
MachineInstr *SaveRegsCall =
BuildMI(MBB, MI, DL, HII.get(Hexagon::SAVE_REGISTERS_CALL_V4))
.addExternalSymbol(SpillFun);
// Add callee-saved registers as use.
addCalleeSaveRegistersAsImpOperand(SaveRegsCall, MaxReg, false);
// Add live in registers.
for (unsigned I = 0; I < CSI.size(); ++I)
MBB.addLiveIn(CSI[I].getReg());
return true;
}
for (unsigned i = 0, n = CSI.size(); i < n; ++i) {
unsigned Reg = CSI[i].getReg();
// Add live in registers. We treat eh_return callee saved register r0 - r3
// specially. They are not really callee saved registers as they are not
// supposed to be killed.
bool IsKill = !HRI.isEHReturnCalleeSaveReg(Reg);
int FI = CSI[i].getFrameIdx();
const TargetRegisterClass *RC = HRI.getMinimalPhysRegClass(Reg);
HII.storeRegToStackSlot(MBB, MI, Reg, IsKill, FI, RC, &HRI);
if (IsKill)
MBB.addLiveIn(Reg);
}
return true;
}
bool HexagonFrameLowering::insertCSRRestoresInBlock(MachineBasicBlock &MBB,
const CSIVect &CSI, const HexagonRegisterInfo &HRI) const {
if (CSI.empty())
return false;
MachineBasicBlock::iterator MI = MBB.getFirstTerminator();
MachineFunction &MF = *MBB.getParent();
auto &HII = *MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
if (useRestoreFunction(MF, CSI)) {
bool HasTC = hasTailCall(MBB) || !hasReturn(MBB);
unsigned MaxR = getMaxCalleeSavedReg(CSI, HRI);
SpillKind Kind = HasTC ? SK_FromMemTailcall : SK_FromMem;
const char *RestoreFn = getSpillFunctionFor(MaxR, Kind);
// Call spill function.
DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc()
: MBB.getLastNonDebugInstr()->getDebugLoc();
MachineInstr *DeallocCall = nullptr;
if (HasTC) {
unsigned ROpc = Hexagon::RESTORE_DEALLOC_BEFORE_TAILCALL_V4;
DeallocCall = BuildMI(MBB, MI, DL, HII.get(ROpc))
.addExternalSymbol(RestoreFn);
} else {
// The block has a return.
MachineBasicBlock::iterator It = MBB.getFirstTerminator();
assert(It->isReturn() && std::next(It) == MBB.end());
unsigned ROpc = Hexagon::RESTORE_DEALLOC_RET_JMP_V4;
DeallocCall = BuildMI(MBB, It, DL, HII.get(ROpc))
.addExternalSymbol(RestoreFn);
// Transfer the function live-out registers.
DeallocCall->copyImplicitOps(MF, It);
}
addCalleeSaveRegistersAsImpOperand(DeallocCall, MaxR, true);
return true;
}
for (unsigned i = 0; i < CSI.size(); ++i) {
unsigned Reg = CSI[i].getReg();
const TargetRegisterClass *RC = HRI.getMinimalPhysRegClass(Reg);
int FI = CSI[i].getFrameIdx();
HII.loadRegFromStackSlot(MBB, MI, Reg, FI, RC, &HRI);
}
return true;
}
void HexagonFrameLowering::eliminateCallFramePseudoInstr(MachineFunction &MF,
MachineBasicBlock &MBB, MachineBasicBlock::iterator I) const {
MachineInstr &MI = *I;
unsigned Opc = MI.getOpcode();
(void)Opc; // Silence compiler warning.
assert((Opc == Hexagon::ADJCALLSTACKDOWN || Opc == Hexagon::ADJCALLSTACKUP) &&
"Cannot handle this call frame pseudo instruction");
MBB.erase(I);
}
void HexagonFrameLowering::processFunctionBeforeFrameFinalized(
MachineFunction &MF, RegScavenger *RS) const {
// If this function has uses aligned stack and also has variable sized stack
// objects, then we need to map all spill slots to fixed positions, so that
// they can be accessed through FP. Otherwise they would have to be accessed
// via AP, which may not be available at the particular place in the program.
MachineFrameInfo *MFI = MF.getFrameInfo();
bool HasAlloca = MFI->hasVarSizedObjects();
bool NeedsAlign = (MFI->getMaxAlignment() > getStackAlignment());
if (!HasAlloca || !NeedsAlign)
return;
unsigned LFS = MFI->getLocalFrameSize();
int Offset = -LFS;
for (int i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
if (!MFI->isSpillSlotObjectIndex(i) || MFI->isDeadObjectIndex(i))
continue;
int S = MFI->getObjectSize(i);
LFS += S;
Offset -= S;
MFI->mapLocalFrameObject(i, Offset);
}
MFI->setLocalFrameSize(LFS);
unsigned A = MFI->getLocalFrameMaxAlign();
assert(A <= 8 && "Unexpected local frame alignment");
if (A == 0)
MFI->setLocalFrameMaxAlign(8);
MFI->setUseLocalStackAllocationBlock(true);
}
/// Returns true if there is no caller saved registers available.
static bool needToReserveScavengingSpillSlots(MachineFunction &MF,
const HexagonRegisterInfo &HRI) {
MachineRegisterInfo &MRI = MF.getRegInfo();
const MCPhysReg *CallerSavedRegs = HRI.getCallerSavedRegs(&MF);
// Check for an unused caller-saved register.
for ( ; *CallerSavedRegs; ++CallerSavedRegs) {
MCPhysReg FreeReg = *CallerSavedRegs;
if (!MRI.reg_nodbg_empty(FreeReg))
continue;
// Check aliased register usage.
bool IsCurrentRegUsed = false;
for (MCRegAliasIterator AI(FreeReg, &HRI, false); AI.isValid(); ++AI)
if (!MRI.reg_nodbg_empty(*AI)) {
IsCurrentRegUsed = true;
break;
}
if (IsCurrentRegUsed)
continue;
// Neither directly used nor used through an aliased register.
return false;
}
// All caller-saved registers are used.
return true;
}
/// Replaces the predicate spill code pseudo instructions by valid instructions.
bool HexagonFrameLowering::replacePredRegPseudoSpillCode(MachineFunction &MF)
const {
auto &HST = static_cast<const HexagonSubtarget&>(MF.getSubtarget());
auto &HII = *HST.getInstrInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
bool HasReplacedPseudoInst = false;
// Replace predicate spill pseudo instructions by real code.
// Loop over all of the basic blocks.
for (MachineFunction::iterator MBBb = MF.begin(), MBBe = MF.end();
MBBb != MBBe; ++MBBb) {
MachineBasicBlock *MBB = &*MBBb;
// Traverse the basic block.
MachineBasicBlock::iterator NextII;
for (MachineBasicBlock::iterator MII = MBB->begin(); MII != MBB->end();
MII = NextII) {
MachineInstr *MI = MII;
NextII = std::next(MII);
int Opc = MI->getOpcode();
if (Opc == Hexagon::STriw_pred) {
HasReplacedPseudoInst = true;
// STriw_pred FI, 0, SrcReg;
unsigned VirtReg = MRI.createVirtualRegister(&Hexagon::IntRegsRegClass);
unsigned SrcReg = MI->getOperand(2).getReg();
bool IsOrigSrcRegKilled = MI->getOperand(2).isKill();
assert(MI->getOperand(0).isFI() && "Expect a frame index");
assert(Hexagon::PredRegsRegClass.contains(SrcReg) &&
"Not a predicate register");
// Insert transfer to general purpose register.
// VirtReg = C2_tfrpr SrcPredReg
BuildMI(*MBB, MII, MI->getDebugLoc(), HII.get(Hexagon::C2_tfrpr),
VirtReg).addReg(SrcReg, getKillRegState(IsOrigSrcRegKilled));
// Change instruction to S2_storeri_io.
// S2_storeri_io FI, 0, VirtReg
MI->setDesc(HII.get(Hexagon::S2_storeri_io));
MI->getOperand(2).setReg(VirtReg);
MI->getOperand(2).setIsKill();
} else if (Opc == Hexagon::LDriw_pred) {
// DstReg = LDriw_pred FI, 0
MachineOperand &M0 = MI->getOperand(0);
if (M0.isDead()) {
MBB->erase(MII);
continue;
}
unsigned VirtReg = MRI.createVirtualRegister(&Hexagon::IntRegsRegClass);
unsigned DestReg = MI->getOperand(0).getReg();
assert(MI->getOperand(1).isFI() && "Expect a frame index");
assert(Hexagon::PredRegsRegClass.contains(DestReg) &&
"Not a predicate register");
// Change instruction to L2_loadri_io.
// VirtReg = L2_loadri_io FI, 0
MI->setDesc(HII.get(Hexagon::L2_loadri_io));
MI->getOperand(0).setReg(VirtReg);
// Insert transfer to general purpose register.
// DestReg = C2_tfrrp VirtReg
const MCInstrDesc &D = HII.get(Hexagon::C2_tfrrp);
BuildMI(*MBB, std::next(MII), MI->getDebugLoc(), D, DestReg)
.addReg(VirtReg, getKillRegState(true));
HasReplacedPseudoInst = true;
}
}
}
return HasReplacedPseudoInst;
}
void HexagonFrameLowering::determineCalleeSaves(MachineFunction &MF,
BitVector &SavedRegs,
RegScavenger *RS) const {
TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
auto &HST = static_cast<const HexagonSubtarget&>(MF.getSubtarget());
auto &HRI = *HST.getRegisterInfo();
bool HasEHReturn = MF.getInfo<HexagonMachineFunctionInfo>()->hasEHReturn();
// If we have a function containing __builtin_eh_return we want to spill and
// restore all callee saved registers. Pretend that they are used.
if (HasEHReturn) {
for (const MCPhysReg *CSRegs = HRI.getCalleeSavedRegs(&MF); *CSRegs;
++CSRegs)
SavedRegs.set(*CSRegs);
}
const TargetRegisterClass &RC = Hexagon::IntRegsRegClass;
// Replace predicate register pseudo spill code.
bool HasReplacedPseudoInst = replacePredRegPseudoSpillCode(MF);
// We need to reserve a a spill slot if scavenging could potentially require
// spilling a scavenged register.
if (HasReplacedPseudoInst && needToReserveScavengingSpillSlots(MF, HRI)) {
MachineFrameInfo *MFI = MF.getFrameInfo();
for (int i=0; i < NumberScavengerSlots; i++)
RS->addScavengingFrameIndex(
MFI->CreateSpillStackObject(RC.getSize(), RC.getAlignment()));
}
}
#ifndef NDEBUG
static void dump_registers(BitVector &Regs, const TargetRegisterInfo &TRI) {
dbgs() << '{';
for (int x = Regs.find_first(); x >= 0; x = Regs.find_next(x)) {
unsigned R = x;
dbgs() << ' ' << PrintReg(R, &TRI);
}
dbgs() << " }";
}
#endif
bool HexagonFrameLowering::assignCalleeSavedSpillSlots(MachineFunction &MF,
const TargetRegisterInfo *TRI, std::vector<CalleeSavedInfo> &CSI) const {
DEBUG(dbgs() << LLVM_FUNCTION_NAME << " on "
<< MF.getFunction()->getName() << '\n');
MachineFrameInfo *MFI = MF.getFrameInfo();
BitVector SRegs(Hexagon::NUM_TARGET_REGS);
// Generate a set of unique, callee-saved registers (SRegs), where each
// register in the set is maximal in terms of sub-/super-register relation,
// i.e. for each R in SRegs, no proper super-register of R is also in SRegs.
// (1) For each callee-saved register, add that register and all of its
// sub-registers to SRegs.
DEBUG(dbgs() << "Initial CS registers: {");
for (unsigned i = 0, n = CSI.size(); i < n; ++i) {
unsigned R = CSI[i].getReg();
DEBUG(dbgs() << ' ' << PrintReg(R, TRI));
for (MCSubRegIterator SR(R, TRI, true); SR.isValid(); ++SR)
SRegs[*SR] = true;
}
DEBUG(dbgs() << " }\n");
DEBUG(dbgs() << "SRegs.1: "; dump_registers(SRegs, *TRI); dbgs() << "\n");
// (2) For each reserved register, remove that register and all of its
// sub- and super-registers from SRegs.
BitVector Reserved = TRI->getReservedRegs(MF);
for (int x = Reserved.find_first(); x >= 0; x = Reserved.find_next(x)) {
unsigned R = x;
for (MCSuperRegIterator SR(R, TRI, true); SR.isValid(); ++SR)
SRegs[*SR] = false;
}
DEBUG(dbgs() << "Res: "; dump_registers(Reserved, *TRI); dbgs() << "\n");
DEBUG(dbgs() << "SRegs.2: "; dump_registers(SRegs, *TRI); dbgs() << "\n");
// (3) Collect all registers that have at least one sub-register in SRegs,
// and also have no sub-registers that are reserved. These will be the can-
// didates for saving as a whole instead of their individual sub-registers.
// (Saving R17:16 instead of R16 is fine, but only if R17 was not reserved.)
BitVector TmpSup(Hexagon::NUM_TARGET_REGS);
for (int x = SRegs.find_first(); x >= 0; x = SRegs.find_next(x)) {
unsigned R = x;
for (MCSuperRegIterator SR(R, TRI); SR.isValid(); ++SR)
TmpSup[*SR] = true;
}
for (int x = TmpSup.find_first(); x >= 0; x = TmpSup.find_next(x)) {
unsigned R = x;
for (MCSubRegIterator SR(R, TRI, true); SR.isValid(); ++SR) {
if (!Reserved[*SR])
continue;
TmpSup[R] = false;
break;
}
}
DEBUG(dbgs() << "TmpSup: "; dump_registers(TmpSup, *TRI); dbgs() << "\n");
// (4) Include all super-registers found in (3) into SRegs.
SRegs |= TmpSup;
DEBUG(dbgs() << "SRegs.4: "; dump_registers(SRegs, *TRI); dbgs() << "\n");
// (5) For each register R in SRegs, if any super-register of R is in SRegs,
// remove R from SRegs.
for (int x = SRegs.find_first(); x >= 0; x = SRegs.find_next(x)) {
unsigned R = x;
for (MCSuperRegIterator SR(R, TRI); SR.isValid(); ++SR) {
if (!SRegs[*SR])
continue;
SRegs[R] = false;
break;
}
}
DEBUG(dbgs() << "SRegs.5: "; dump_registers(SRegs, *TRI); dbgs() << "\n");
// Now, for each register that has a fixed stack slot, create the stack
// object for it.
CSI.clear();
typedef TargetFrameLowering::SpillSlot SpillSlot;
unsigned NumFixed;
int MinOffset = 0; // CS offsets are negative.
const SpillSlot *FixedSlots = getCalleeSavedSpillSlots(NumFixed);
for (const SpillSlot *S = FixedSlots; S != FixedSlots+NumFixed; ++S) {
if (!SRegs[S->Reg])
continue;
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(S->Reg);
int FI = MFI->CreateFixedSpillStackObject(RC->getSize(), S->Offset);
MinOffset = std::min(MinOffset, S->Offset);
CSI.push_back(CalleeSavedInfo(S->Reg, FI));
SRegs[S->Reg] = false;
}
// There can be some registers that don't have fixed slots. For example,
// we need to store R0-R3 in functions with exception handling. For each
// such register, create a non-fixed stack object.
for (int x = SRegs.find_first(); x >= 0; x = SRegs.find_next(x)) {
unsigned R = x;
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(R);
int Off = MinOffset - RC->getSize();
unsigned Align = std::min(RC->getAlignment(), getStackAlignment());
assert(isPowerOf2_32(Align));
Off &= -Align;
int FI = MFI->CreateFixedSpillStackObject(RC->getSize(), Off);
MinOffset = std::min(MinOffset, Off);
CSI.push_back(CalleeSavedInfo(R, FI));
SRegs[R] = false;
}
DEBUG({
dbgs() << "CS information: {";
for (unsigned i = 0, n = CSI.size(); i < n; ++i) {
int FI = CSI[i].getFrameIdx();
int Off = MFI->getObjectOffset(FI);
dbgs() << ' ' << PrintReg(CSI[i].getReg(), TRI) << ":fi#" << FI << ":sp";
if (Off >= 0)
dbgs() << '+';
dbgs() << Off;
}
dbgs() << " }\n";
});
#ifndef NDEBUG
// Verify that all registers were handled.
bool MissedReg = false;
for (int x = SRegs.find_first(); x >= 0; x = SRegs.find_next(x)) {
unsigned R = x;
dbgs() << PrintReg(R, TRI) << ' ';
MissedReg = true;
}
if (MissedReg)
llvm_unreachable("...there are unhandled callee-saved registers!");
#endif
return true;
}
void HexagonFrameLowering::expandAlloca(MachineInstr *AI,
const HexagonInstrInfo &HII, unsigned SP, unsigned CF) const {
MachineBasicBlock &MB = *AI->getParent();
DebugLoc DL = AI->getDebugLoc();
unsigned A = AI->getOperand(2).getImm();
// Have
// Rd = alloca Rs, #A
//
// If Rs and Rd are different registers, use this sequence:
// Rd = sub(r29, Rs)
// r29 = sub(r29, Rs)
// Rd = and(Rd, #-A) ; if necessary
// r29 = and(r29, #-A) ; if necessary
// Rd = add(Rd, #CF) ; CF size aligned to at most A
// otherwise, do
// Rd = sub(r29, Rs)
// Rd = and(Rd, #-A) ; if necessary
// r29 = Rd
// Rd = add(Rd, #CF) ; CF size aligned to at most A
MachineOperand &RdOp = AI->getOperand(0);
MachineOperand &RsOp = AI->getOperand(1);
unsigned Rd = RdOp.getReg(), Rs = RsOp.getReg();
// Rd = sub(r29, Rs)
BuildMI(MB, AI, DL, HII.get(Hexagon::A2_sub), Rd)
.addReg(SP)
.addReg(Rs);
if (Rs != Rd) {
// r29 = sub(r29, Rs)
BuildMI(MB, AI, DL, HII.get(Hexagon::A2_sub), SP)
.addReg(SP)
.addReg(Rs);
}
if (A > 8) {
// Rd = and(Rd, #-A)
BuildMI(MB, AI, DL, HII.get(Hexagon::A2_andir), Rd)
.addReg(Rd)
.addImm(-int64_t(A));
if (Rs != Rd)
BuildMI(MB, AI, DL, HII.get(Hexagon::A2_andir), SP)
.addReg(SP)
.addImm(-int64_t(A));
}
if (Rs == Rd) {
// r29 = Rd
BuildMI(MB, AI, DL, HII.get(TargetOpcode::COPY), SP)
.addReg(Rd);
}
if (CF > 0) {
// Rd = add(Rd, #CF)
BuildMI(MB, AI, DL, HII.get(Hexagon::A2_addi), Rd)
.addReg(Rd)
.addImm(CF);
}
}
bool HexagonFrameLowering::needsAligna(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
if (!MFI->hasVarSizedObjects())
return false;
unsigned MaxA = MFI->getMaxAlignment();
if (MaxA <= getStackAlignment())
return false;
return true;
}
const MachineInstr *HexagonFrameLowering::getAlignaInstr(
const MachineFunction &MF) const {
for (auto &B : MF)
for (auto &I : B)
if (I.getOpcode() == Hexagon::ALIGNA)
return &I;
return nullptr;
}
// FIXME: Use Function::optForSize().
inline static bool isOptSize(const MachineFunction &MF) {
AttributeSet AF = MF.getFunction()->getAttributes();
return AF.hasAttribute(AttributeSet::FunctionIndex,
Attribute::OptimizeForSize);
}
inline static bool isMinSize(const MachineFunction &MF) {
return MF.getFunction()->optForMinSize();
}
/// Determine whether the callee-saved register saves and restores should
/// be generated via inline code. If this function returns "true", inline
/// code will be generated. If this function returns "false", additional
/// checks are performed, which may still lead to the inline code.
bool HexagonFrameLowering::shouldInlineCSR(MachineFunction &MF,
const CSIVect &CSI) const {
if (MF.getInfo<HexagonMachineFunctionInfo>()->hasEHReturn())
return true;
if (!isOptSize(MF) && !isMinSize(MF))
if (MF.getTarget().getOptLevel() > CodeGenOpt::Default)
return true;
// Check if CSI only has double registers, and if the registers form
// a contiguous block starting from D8.
BitVector Regs(Hexagon::NUM_TARGET_REGS);
for (unsigned i = 0, n = CSI.size(); i < n; ++i) {
unsigned R = CSI[i].getReg();
if (!Hexagon::DoubleRegsRegClass.contains(R))
return true;
Regs[R] = true;
}
int F = Regs.find_first();
if (F != Hexagon::D8)
return true;
while (F >= 0) {
int N = Regs.find_next(F);
if (N >= 0 && N != F+1)
return true;
F = N;
}
return false;
}
bool HexagonFrameLowering::useSpillFunction(MachineFunction &MF,
const CSIVect &CSI) const {
if (shouldInlineCSR(MF, CSI))
return false;
unsigned NumCSI = CSI.size();
if (NumCSI <= 1)
return false;
unsigned Threshold = isOptSize(MF) ? SpillFuncThresholdOs
: SpillFuncThreshold;
return Threshold < NumCSI;
}
bool HexagonFrameLowering::useRestoreFunction(MachineFunction &MF,
const CSIVect &CSI) const {
if (shouldInlineCSR(MF, CSI))
return false;
unsigned NumCSI = CSI.size();
unsigned Threshold = isOptSize(MF) ? SpillFuncThresholdOs-1
: SpillFuncThreshold;
return Threshold < NumCSI;
}
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