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[AArch64] Implement stack probing for windows
Differential Revision: https://reviews.llvm.org/D41131 llvm-svn: 321150
This commit is contained in:
Martin Storsjo
parent
a9fd04c09d
commit
786b1663a9
@ -288,3 +288,31 @@ standard stack probe emission.
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The MSVC environment does not emit code for VLAs currently.
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Windows on ARM64
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----------------
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Stack Probe Emission
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^^^^^^^^^^^^^^^^^^^^
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The reference implementation (Microsoft Visual Studio 2017) emits stack probes
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in the following fashion:
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.. code-block:: gas
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mov x15, #constant
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bl __chkstk
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sub sp, sp, x15, lsl #4
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However, this has the limitation of 256 MiB (±128MiB). In order to accommodate
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larger binaries, LLVM supports the use of ``-mcode-model=large`` to allow a 8GiB
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(±4GiB) range via a slight deviation. It will generate an indirect jump as
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follows:
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.. code-block:: gas
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mov x15, #constant
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adrp x16, __chkstk
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add x16, x16, :lo12:__chkstk
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blr x16
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sub sp, sp, x15, lsl #4
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@ -97,6 +97,7 @@
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#include "AArch64RegisterInfo.h"
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#include "AArch64Subtarget.h"
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#include "AArch64TargetMachine.h"
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#include "MCTargetDesc/AArch64AddressingModes.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/CodeGen/LivePhysRegs.h"
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@ -335,6 +336,22 @@ bool AArch64FrameLowering::canUseAsPrologue(
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return findScratchNonCalleeSaveRegister(TmpMBB) != AArch64::NoRegister;
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}
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static bool windowsRequiresStackProbe(MachineFunction &MF,
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unsigned StackSizeInBytes) {
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const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
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if (!Subtarget.isTargetWindows())
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return false;
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const Function &F = MF.getFunction();
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// TODO: When implementing stack protectors, take that into account
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// for the probe threshold.
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unsigned StackProbeSize = 4096;
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if (F.hasFnAttribute("stack-probe-size"))
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F.getFnAttribute("stack-probe-size")
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.getValueAsString()
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.getAsInteger(0, StackProbeSize);
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return StackSizeInBytes >= StackProbeSize;
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}
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bool AArch64FrameLowering::shouldCombineCSRLocalStackBump(
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MachineFunction &MF, unsigned StackBumpBytes) const {
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AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
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@ -347,7 +364,7 @@ bool AArch64FrameLowering::shouldCombineCSRLocalStackBump(
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// 512 is the maximum immediate for stp/ldp that will be used for
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// callee-save save/restores
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if (StackBumpBytes >= 512)
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if (StackBumpBytes >= 512 || windowsRequiresStackProbe(MF, StackBumpBytes))
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return false;
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if (MFI.hasVarSizedObjects())
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@ -478,7 +495,7 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
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return;
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int NumBytes = (int)MFI.getStackSize();
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if (!AFI->hasStackFrame()) {
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if (!AFI->hasStackFrame() && !windowsRequiresStackProbe(MF, NumBytes)) {
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assert(!HasFP && "unexpected function without stack frame but with FP");
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// All of the stack allocation is for locals.
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@ -550,6 +567,44 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
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MachineInstr::FrameSetup);
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}
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if (windowsRequiresStackProbe(MF, NumBytes)) {
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uint32_t NumWords = NumBytes >> 4;
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BuildMI(MBB, MBBI, DL, TII->get(AArch64::MOVi64imm), AArch64::X15)
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.addImm(NumWords)
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.setMIFlags(MachineInstr::FrameSetup);
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switch (MF.getTarget().getCodeModel()) {
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case CodeModel::Small:
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case CodeModel::Medium:
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case CodeModel::Kernel:
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BuildMI(MBB, MBBI, DL, TII->get(AArch64::BL))
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.addExternalSymbol("__chkstk")
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.addReg(AArch64::X15, RegState::Implicit)
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.setMIFlags(MachineInstr::FrameSetup);
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break;
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case CodeModel::Large:
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BuildMI(MBB, MBBI, DL, TII->get(AArch64::MOVaddrEXT))
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.addReg(AArch64::X16, RegState::Define)
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.addExternalSymbol("__chkstk")
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.addExternalSymbol("__chkstk")
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.setMIFlags(MachineInstr::FrameSetup);
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BuildMI(MBB, MBBI, DL, TII->get(AArch64::BLR))
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.addReg(AArch64::X16, RegState::Kill)
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.addReg(AArch64::X15, RegState::Implicit | RegState::Define)
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.setMIFlags(MachineInstr::FrameSetup);
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break;
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}
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BuildMI(MBB, MBBI, DL, TII->get(AArch64::SUBXrx64), AArch64::SP)
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.addReg(AArch64::SP, RegState::Kill)
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.addReg(AArch64::X15, RegState::Kill)
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.addImm(AArch64_AM::getArithExtendImm(AArch64_AM::UXTX, 4))
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.setMIFlags(MachineInstr::FrameSetup);
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NumBytes = 0;
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}
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// Allocate space for the rest of the frame.
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if (NumBytes) {
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const bool NeedsRealignment = RegInfo->needsStackRealignment(MF);
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@ -1164,18 +1219,32 @@ void AArch64FrameLowering::determineCalleeSaves(MachineFunction &MF,
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unsigned UnspilledCSGPR = AArch64::NoRegister;
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unsigned UnspilledCSGPRPaired = AArch64::NoRegister;
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MachineFrameInfo &MFI = MF.getFrameInfo();
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const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF);
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unsigned BasePointerReg = RegInfo->hasBasePointer(MF)
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? RegInfo->getBaseRegister()
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: (unsigned)AArch64::NoRegister;
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unsigned SpillEstimate = SavedRegs.count();
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for (unsigned i = 0; CSRegs[i]; ++i) {
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unsigned Reg = CSRegs[i];
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unsigned PairedReg = CSRegs[i ^ 1];
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if (Reg == BasePointerReg)
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SpillEstimate++;
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if (produceCompactUnwindFrame(MF) && !SavedRegs.test(PairedReg))
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SpillEstimate++;
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}
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SpillEstimate += 2; // Conservatively include FP+LR in the estimate
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unsigned StackEstimate = MFI.estimateStackSize(MF) + 8 * SpillEstimate;
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// The frame record needs to be created by saving the appropriate registers
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if (hasFP(MF)) {
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if (hasFP(MF) || windowsRequiresStackProbe(MF, StackEstimate)) {
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SavedRegs.set(AArch64::FP);
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SavedRegs.set(AArch64::LR);
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}
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unsigned BasePointerReg = AArch64::NoRegister;
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if (RegInfo->hasBasePointer(MF))
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BasePointerReg = RegInfo->getBaseRegister();
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unsigned ExtraCSSpill = 0;
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const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF);
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// Figure out which callee-saved registers to save/restore.
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for (unsigned i = 0; CSRegs[i]; ++i) {
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const unsigned Reg = CSRegs[i];
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@ -1217,7 +1286,6 @@ void AArch64FrameLowering::determineCalleeSaves(MachineFunction &MF,
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// The CSR spill slots have not been allocated yet, so estimateStackSize
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// won't include them.
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MachineFrameInfo &MFI = MF.getFrameInfo();
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unsigned CFSize = MFI.estimateStackSize(MF) + 8 * NumRegsSpilled;
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DEBUG(dbgs() << "Estimated stack frame size: " << CFSize << " bytes.\n");
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unsigned EstimatedStackSizeLimit = estimateRSStackSizeLimit(MF);
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25
test/CodeGen/AArch64/chkstk.ll
Normal file
25
test/CodeGen/AArch64/chkstk.ll
Normal file
@ -0,0 +1,25 @@
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; RUN: llc -mtriple=aarch64-windows -verify-machineinstrs %s -o - \
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; RUN: | FileCheck -check-prefix CHECK-DEFAULT-CODE-MODEL %s
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; RUN: llc -mtriple=aarch64-windows -verify-machineinstrs -code-model=large %s -o - \
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; RUN: | FileCheck -check-prefix CHECK-LARGE-CODE-MODEL %s
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define void @check_watermark() {
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entry:
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%buffer = alloca [4096 x i8], align 1
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ret void
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}
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; CHECK-DEFAULT-CODE-MODEL: check_watermark:
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; CHECK-DEFAULT-CODE-MODEL-DAG: stp x29, x30, [sp
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; CHECK-DEFAULT-CODE-MODEL-DAG: orr x15, xzr, #0x100
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; CHECK-DEFAULT-CODE-MODEL: bl __chkstk
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; CHECK-DEFAULT-CODE-MODEL: sub sp, sp, x15, lsl #4
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; CHECK-LARGE-CODE-MODEL: check_watermark:
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; CHECK-LARGE-CODE-MODEL-DAG: stp x29, x30, [sp
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; CHECK-LARGE-CODE-MODEL-DAG: orr x15, xzr, #0x100
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; CHECK-LARGE-CODE-MODEL-DAG: adrp x16, __chkstk
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; CHECK-LARGE-CODE-MODEL-DAG: add x16, x16, __chkstk
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; CHECK-LARGE-CODE-MODEL: blr x16
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; CHECK-LARGE-CODE-MODEL: sub sp, sp, x15, lsl #4
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