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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/STLExtras.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Type.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MachineLocation.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<bool>
DisableProEpilogCodeMerge("disable-hexagon-prolog-epilog-code-merge",
cl::Hidden, cl::desc("Disable prolog/epilog code merge"), cl::init(false),
cl::ZeroOrMore);
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);
/// 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.
static 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 biggest callee saved register in the vector.
static 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;
}
void HexagonFrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front();
MachineFrameInfo *MFI = MF.getFrameInfo();
MachineModuleInfo &MMI = MF.getMMI();
MachineBasicBlock::iterator MBBI = MBB.begin();
auto &HTM = static_cast<const HexagonTargetMachine&>(MF.getTarget());
auto &HST = static_cast<const HexagonSubtarget&>(MF.getSubtarget());
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 > 8);
// Check if frame moves are needed for EH.
bool needsFrameMoves = MMI.hasDebugInfo() ||
MF.getFunction()->needsUnwindTableEntry();
// 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();
}
//
// Only 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.
//
bool NoOpt = (HTM.getOptLevel() == CodeGenOpt::None);
if (!NoOpt && !FuncInfo->hasClobberLR() && !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));
}
if (needsFrameMoves) {
std::vector<MCCFIInstruction> Instructions = MMI.getFrameInstructions();
MCSymbol *FrameLabel = MMI.getContext().CreateTempSymbol();
// Advance CFA. DW_CFA_def_cfa
unsigned DwFPReg = HRI.getDwarfRegNum(HRI.getFrameRegister(), true);
unsigned DwRAReg = HRI.getDwarfRegNum(HRI.getRARegister(), true);
// CFA = FP + 8
unsigned CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfa(
FrameLabel, DwFPReg, -8));
BuildMI(MBB, MBBI, dl, HII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// R31 (return addr) = CFA - #4
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
FrameLabel, DwRAReg, -4));
BuildMI(MBB, MBBI, dl, HII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// R30 (frame ptr) = CFA - #8)
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
FrameLabel, DwFPReg, -8));
BuildMI(MBB, MBBI, dl, HII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
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) {
for (unsigned I = 0, E = CSI.size(); I < E; ++I) {
if (CSI[I].getReg() == regsToMove[i]) {
// Subtract 8 to make room for R30 and R31, which are added above.
int64_t Offset = getFrameIndexOffset(MF, CSI[I].getFrameIdx()) - 8;
if (regsToMove[i] < Hexagon::D0 || regsToMove[i] > Hexagon::D15) {
unsigned DwarfReg = HRI.getDwarfRegNum(regsToMove[i], true);
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(FrameLabel,
DwarfReg, Offset));
BuildMI(MBB, MBBI, dl, HII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
} 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 = getMax32BitSubRegister(regsToMove[i], &HRI);
unsigned LoReg = getMax32BitSubRegister(regsToMove[i], &HRI, false);
unsigned HiDwarfReg = HRI.getDwarfRegNum(HiReg, true);
unsigned LoDwarfReg = HRI.getDwarfRegNum(LoReg, true);
unsigned HiCFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(FrameLabel,
HiDwarfReg, Offset+4));
BuildMI(MBB, MBBI, dl, HII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(HiCFIIndex);
unsigned LoCFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(FrameLabel,
LoDwarfReg, Offset));
BuildMI(MBB, MBBI, dl, HII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(LoCFIIndex);
}
break;
}
} // for CSI.size()
} // for regsToMove
} // needsFrameMoves
}
// Returns true if MBB has a machine instructions that indicates a tail call
// in the block.
bool HexagonFrameLowering::hasTailCall(MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
unsigned RetOpcode = MBBI->getOpcode();
return RetOpcode == Hexagon::TCRETURNi || RetOpcode == Hexagon::TCRETURNr;
}
void HexagonFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
//
// Only insert deallocframe if we need to. Also at -O0. See comment
// in emitPrologue above.
//
if (!hasFP(MF) && MF.getTarget().getOptLevel() != CodeGenOpt::None)
return;
auto &HST = static_cast<const HexagonSubtarget&>(MF.getSubtarget());
auto &HII = *HST.getInstrInfo();
MachineBasicBlock::iterator MBBI = std::prev(MBB.end());
MachineBasicBlock::iterator MBBI_end = MBB.end();
DebugLoc dl = MBBI->getDebugLoc();
// Handle EH_RETURN.
if (MBBI->getOpcode() == Hexagon::EH_RETURN_JMPR) {
MachineOperand &OffsetReg = MBBI->getOperand(0);
assert(OffsetReg.isReg() && "Offset should be in register!");
BuildMI(MBB, MBBI, dl, HII.get(Hexagon::L2_deallocframe));
BuildMI(MBB, MBBI, dl, HII.get(Hexagon::A2_add),
Hexagon::R29).addReg(Hexagon::R29).addReg(Hexagon::R28);
return;
}
// Replace 'jumpr r31' instruction with dealloc_return for V4 and higher
// versions.
if (MBBI->getOpcode() == Hexagon::JMPret && !DisableDeallocRet) {
// Check for RESTORE_DEALLOC_RET_JMP_V4 call. Don't emit an extra DEALLOC
// instruction if we encounter it.
MachineBasicBlock::iterator BeforeJMPR =
MBB.begin() == MBBI ? MBBI : std::prev(MBBI);
if (BeforeJMPR != MBBI &&
BeforeJMPR->getOpcode() == Hexagon::RESTORE_DEALLOC_RET_JMP_V4) {
// Remove the JMPR node.
MBB.erase(MBBI);
return;
}
// Add dealloc_return.
MachineInstrBuilder MIB =
BuildMI(MBB, MBBI_end, dl, HII.get(Hexagon::L4_return));
// Transfer the function live-out registers.
MIB->copyImplicitOps(*MBB.getParent(), &*MBBI);
// Remove the JUMPR node.
MBB.erase(MBBI);
} else { // Add deallocframe for tail calls.
// Check for RESTORE_DEALLOC_BEFORE_TAILCALL_V4. We don't need an extra
// L2_deallocframe instruction after it.
MachineBasicBlock::iterator Term = MBB.getFirstTerminator();
MachineBasicBlock::iterator I =
Term == MBB.begin() ? MBB.end() : std::prev(Term);
if (I != MBB.end() &&
I->getOpcode() == Hexagon::RESTORE_DEALLOC_BEFORE_TAILCALL_V4)
return;
BuildMI(MBB, MBBI, dl, HII.get(Hexagon::L2_deallocframe));
}
}
bool HexagonFrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const HexagonMachineFunctionInfo *FuncInfo =
MF.getInfo<HexagonMachineFunctionInfo>();
return (MFI->hasCalls() || (MFI->getStackSize() > 0) ||
FuncInfo->hasClobberLR() );
}
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:
assert(false && "Unhandled maximum callee save register");
break;
}
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);
}
}
/// Returns true if we have V4 operations, optimization level is equal to
/// O2 or Os and exception handling is not required.
static bool shouldOptimizeForSize(MachineFunction &MF) {
if (MF.getInfo<HexagonMachineFunctionInfo>()->hasEHReturn())
return false;
if (MF.getTarget().getOptLevel() == CodeGenOpt::Default) /* -O2 or -Os */
return true;
const Function *F = MF.getFunction();
if (F->hasFnAttribute(Attribute::MinSize))
return true;
return F->hasFnAttribute(Attribute::OptimizeForSize);
}
bool
HexagonFrameLowering::spillCalleeSavedRegisters(
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
MachineFunction *MF = MBB.getParent();
const TargetInstrInfo &TII = *MF->getSubtarget().getInstrInfo();
const HexagonRegisterInfo *HRI =
static_cast<const HexagonRegisterInfo*>(TRI);
if (CSI.empty()) {
return false;
}
// Check whether we should emit a function call to spill the registers.
bool ShouldOptimizeForSize = shouldOptimizeForSize(*MF);
if (ShouldOptimizeForSize && !DisableProEpilogCodeMerge) {
// We have different cut offs when we use callee saved stubs at -Os.
bool HasOptimizeForSizeAttr = MF->getFunction()->getAttributes()
.hasAttribute(AttributeSet::FunctionIndex, Attribute::OptimizeForSize);
unsigned CalleeSavedStubCutOff = HasOptimizeForSizeAttr ?
SpillFuncThresholdOs : SpillFuncThreshold;
// Use a function call if we have to spill registers.
if (CSI.size() > CalleeSavedStubCutOff) {
unsigned MaxReg = getMaxCalleeSavedReg(CSI, TRI);
const char *SpillFun = getSpillFunctionFor(MaxReg, SK_ToMem);
// Call spill function.
DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
MachineInstr *SaveRegsCall =
BuildMI(MBB, MI, DL, TII.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; i < CSI.size(); ++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 IsEHReturnCalleeSavedReg = HRI->isEHReturnCalleeSaveReg(Reg);
if (HRI->isCalleeSaveReg(Reg)) {
int FrameIdx = CSI[i].getFrameIdx();
const TargetRegisterClass *RegClass =
TRI->getMinimalPhysRegClass(Reg);
TII.storeRegToStackSlot(MBB, MI, Reg, !IsEHReturnCalleeSavedReg,
FrameIdx, RegClass, TRI);
if (!IsEHReturnCalleeSavedReg)
MBB.addLiveIn(Reg);
} else {
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.storeRegToStackSlot(MBB, MI, Reg, !IsEHReturnCalleeSavedReg,
CSI[i].getFrameIdx(), RC, TRI);
if (!IsEHReturnCalleeSavedReg)
MBB.addLiveIn(Reg);
}
}
return true;
}
bool HexagonFrameLowering::restoreCalleeSavedRegisters(
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
MachineFunction *MF = MBB.getParent();
const TargetInstrInfo &TII = *MF->getSubtarget().getInstrInfo();
if (CSI.empty()) {
return false;
}
// Check whether we should emit a function call to spill the registers.
bool ShouldOptimizeForSize = shouldOptimizeForSize(*MF);
if (ShouldOptimizeForSize && !DisableProEpilogCodeMerge) {
// We have different cut offs when we use callee saved stubs at -Os.
bool HasOptimizeForSizeAttr = MF->getFunction()->getAttributes()
.hasAttribute(AttributeSet::FunctionIndex, Attribute::OptimizeForSize);
unsigned CalleeSavedStubCutOff = HasOptimizeForSizeAttr ?
(SpillFuncThresholdOs - 1) : SpillFuncThreshold;
// Use a function call if we have to spill registers.
if (CSI.size() > CalleeSavedStubCutOff) {
bool IsTailCallBB = hasTailCall(MBB);
unsigned MaxReg = getMaxCalleeSavedReg(CSI, TRI);
const char *SpillFun =
getSpillFunctionFor(MaxReg, IsTailCallBB ?
SK_FromMemTailcall : SK_FromMem);
// Call spill function.
DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
MachineInstr *DeallocCall = nullptr;
if (IsTailCallBB) {
DeallocCall = BuildMI(MBB, MI, DL,
TII.get(Hexagon::RESTORE_DEALLOC_BEFORE_TAILCALL_V4))
.addExternalSymbol(SpillFun);
}
else {
MachineBasicBlock::iterator JumprInst = std::prev(MBB.end());
assert(JumprInst->getOpcode() == Hexagon::JMPret);
DeallocCall =
BuildMI(MBB, MI, DL, TII.get(Hexagon::RESTORE_DEALLOC_RET_JMP_V4))
.addExternalSymbol(SpillFun);
// Transfer the function live-out registers.
DeallocCall->copyImplicitOps(*MBB.getParent(), JumprInst);
}
addCalleeSaveRegistersAsImpOperand(DeallocCall, MaxReg, true);
return true;
}
}
const HexagonRegisterInfo *HRI =
static_cast<const HexagonRegisterInfo*>(TRI);
for (unsigned i = 0; i < CSI.size(); ++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 IsEHReturnCalleeSavedReg = HRI->isEHReturnCalleeSaveReg(Reg);
if (HRI->isCalleeSaveReg(Reg)) {
int FrameIdx = CSI[i].getFrameIdx();
const TargetRegisterClass *RegClass =
TRI->getMinimalPhysRegClass(Reg);
TII.loadRegFromStackSlot(MBB, MI, Reg, FrameIdx,
RegClass, TRI);
if (!IsEHReturnCalleeSavedReg)
MBB.addLiveIn(Reg);
} else {
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.loadRegFromStackSlot(MBB, MI, Reg, CSI[i].getFrameIdx(), RC, TRI);
if (!IsEHReturnCalleeSavedReg)
MBB.addLiveIn(Reg);
}
}
return true;
}
void HexagonFrameLowering::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
MachineInstr &MI = *I;
unsigned Opc = MI.getOpcode();
assert((Opc == Hexagon::ADJCALLSTACKDOWN || Opc == Hexagon::ADJCALLSTACKUP) &&
"Cannot handle this call frame pseudo instruction");
MBB.erase(I);
}
int HexagonFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
int FI) const {
return MF.getFrameInfo()->getObjectOffset(FI);
}
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 HasAligna = (MFI->getMaxAlignment() > getStackAlignment());
if (!HasAlloca || !HasAligna)
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 uint16_t *CallerSavedRegs = HRI.getCallerSavedRegs(&MF);
// Check for an unused caller-saved register.
for ( ; *CallerSavedRegs; ++CallerSavedRegs) {
unsigned FreeReg = *CallerSavedRegs;
if (MRI.isPhysRegUsed(FreeReg))
continue;
// Check aliased register usage.
bool IsCurrentRegUsed = false;
for (MCRegAliasIterator AI(FreeReg, &HRI, false); AI.isValid(); ++AI)
if (MRI.isPhysRegUsed(*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;
}
/// Marks physical registers as used so that the callee-saved registers are
/// always a multiple of two.
void HexagonFrameLowering::
adjustForCalleeSavedRegsSpillCall(MachineFunction &MF) const {
// We need to pretend that the callee-saved registers are a multiple of two
// because there are only library functions to handle those cases.
// (save_r16_to_17, save_r16_to_r19, ...)
MachineRegisterInfo &MRI = MF.getRegInfo();
const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
const uint16_t *CSRegs = TRI.getCalleeSavedRegs(&MF);
// Compute the smallest and biggest callee-saved register used.
unsigned Biggest = 0;
unsigned Smallest = Hexagon::R31;
unsigned NumUsed = 0;
for (; *CSRegs; ++CSRegs){
unsigned CurrCSR = *CSRegs;
if (MRI.isPhysRegUsed(CurrCSR)) {
++NumUsed;
if (CurrCSR >= Biggest)
Biggest = CurrCSR;
if (CurrCSR <= Smallest)
Smallest = CurrCSR;
continue;
}
// Also check alias registers.
for (MCRegAliasIterator AI(CurrCSR, &TRI, false); AI.isValid(); ++AI) {
if (MRI.isPhysRegUsed(*AI)) {
++NumUsed;
if (CurrCSR >= Biggest)
Biggest = CurrCSR;
if (CurrCSR <= Smallest)
Smallest = CurrCSR;
break;
}
}
}
// Don't do anything if the number of register used is zero.
if (NumUsed == 0)
return;
// Ensure that the biggest register is r17, r19, ...
if ((Biggest - Hexagon::R0) % 2 == 0)
++Biggest;
assert(Smallest != Hexagon::R31 && "Should not happen");
// Make sure all the physical register are marked as used so that they are
// assigned stack slots.
for (unsigned I = Smallest; I <= Biggest; ++I)
if (!MRI.isPhysRegUsed(I))
MRI.setPhysRegUsed(I);
}
/// 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::processFunctionBeforeCalleeSavedScan(
MachineFunction &MF, RegScavenger* RS) const {
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) {
MachineRegisterInfo &MRI = MF.getRegInfo();
for (const uint16_t *CSRegs = HRI.getCalleeSavedRegs(&MF); *CSRegs;
++CSRegs)
if (!MRI.isPhysRegUsed(*CSRegs))
MRI.setPhysRegUsed(*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()));
}
bool ShouldOptimizeForSize = shouldOptimizeForSize(MF);
// Do nothing if we are not optimizing for size.
if (!ShouldOptimizeForSize || DisableProEpilogCodeMerge)
return;
// Adjust the used callee save registers to be a multiple of two as there are
// only library functions for them.
adjustForCalleeSavedRegsSpillCall(MF);
}
bool HexagonFrameLowering::assignCalleeSavedSpillSlots(MachineFunction &MF,
const TargetRegisterInfo *TRI, std::vector<CalleeSavedInfo> &CSI) const {
const Function &F = *MF.getFunction();
DEBUG(dbgs() << LLVM_FUNCTION_NAME << " on " << F.getName() << '\n');
MachineFrameInfo *MFI = MF.getFrameInfo();
unsigned NR = TRI->getNumRegs();
BitVector SRegs(NR);
// 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.
// 1a. For each callee-saved register, add that register 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");
// 1b. Collect all registers that have at least one sub-registers in SRegs.
BitVector TmpSup(NR);
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;
}
// 1c. Out of all the super-registers found in 1b, add to SRegs those of
// them, whose all sub-registers are already in SReg, or will be added to
// SReg (i.e. are in TmpSup).
// At the end of this step, the following will be true:
// R \in SRegs => (if S is sub-register of R, then S \in SRegs)
// S1..Sn = { sub-registers of R }, and S1..Sn \in SRegs => R \in SRegs
for (int x = TmpSup.find_first(); x >= 0; x = TmpSup.find_next(x)) {
unsigned R = x;
bool AllSub = true;
for (MCSubRegIterator SR(R, TRI); SR.isValid(); ++SR) {
if (SRegs[*SR] || TmpSup[*SR])
continue;
AllSub = false;
break;
}
// On Hexagon, a super-register is covered by its sub-registers.
if (AllSub)
SRegs[R] = true;
}
// 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 (MCSubRegIterator SR(R, TRI, true); SR.isValid(); ++SR)
SRegs[*SR] = false;
for (MCSuperRegIterator SR(R, TRI); SR.isValid(); ++SR)
SRegs[*SR] = false;
}
// 3. 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;
}
}
// 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 &TII, 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, TII.get(Hexagon::A2_sub), Rd)
.addReg(SP)
.addReg(Rs);
if (Rs != Rd) {
// r29 = sub(r29, Rs)
BuildMI(MB, AI, DL, TII.get(Hexagon::A2_sub), SP)
.addReg(SP)
.addReg(Rs);
}
if (A > 8) {
// Rd = and(Rd, #-A)
BuildMI(MB, AI, DL, TII.get(Hexagon::A2_andir), Rd)
.addReg(Rd)
.addImm(-int64_t(A));
if (Rs != Rd)
BuildMI(MB, AI, DL, TII.get(Hexagon::A2_andir), SP)
.addReg(SP)
.addImm(-int64_t(A));
}
if (Rs == Rd) {
// r29 = Rd
BuildMI(MB, AI, DL, TII.get(TargetOpcode::COPY), SP)
.addReg(Rd);
}
if (CF > 0) {
// Rd = add(Rd, #CF)
BuildMI(MB, AI, DL, TII.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;
}
MachineInstr *HexagonFrameLowering::getAlignaInstr(MachineFunction &MF) const {
for (auto &B : MF)
for (auto &I : B)
if (I.getOpcode() == Hexagon::ALIGNA)
return &I;
return nullptr;
}
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