[llvm] r207615 - ARM: support stack probe emission for Windows on ARM
Saleem Abdulrasool
compnerd at compnerd.org
Wed Apr 30 21:28:34 PDT 2014
On Wed, Apr 30, 2014 at 1:42 AM, Kostya Serebryany <kcc at google.com> wrote:
> I observe a leak report when running this test under lsan or valgrind (
> http://llvm.org/bugs/show_bug.cgi?id=19521).
> Please check.
>
Thank you for bringing this to my attention. I believe that the leak
should be addressed by SVN r207737. At the very least, valgrind seems to
be happy with it now.
Indirect leak of 136 byte(s) in 1 object(s) allocated from:
>
> #0 0x65f540 in operator new(unsigned long)
> projects/compiler-rt/lib/asan/asan_new_delete.cc:62
> #1 0x20909d3 in llvm::User::operator new(unsigned long, unsigned int)
> lib/IR/User.cpp:60
> #2 0xa8bb12 in Twine include/llvm/IR/Function.h:131
>
> #3 0xa8bb12 in
> llvm::ARMFrameLowering::emitPrologue(llvm::MachineFunction&) const
> lib/Target/ARM/ARMFrameLowering.cpp:322
> #4 0x1c49990 in
> llvm::PEI::insertPrologEpilogCode(llvm::MachineFunction&)
> lib/CodeGen/PrologEpilogInserter.cpp:671
> #5 0x1c43127 in
> llvm::PEI::runOnMachineFunction(llvm::MachineFunction&)
> lib/CodeGen/PrologEpilogInserter.cpp:155
> #6 0x1b2cbfb in
> llvm::MachineFunctionPass::runOnFunction(llvm::Function&)
> lib/CodeGen/MachineFunctionPass.cpp:33
> #7 0x204ee04 in llvm::FPPassManager::runOnFunction(llvm::Function&)
> lib/IR/LegacyPassManager.cpp:1545
> #8 0x204f315 in llvm::FPPassManager::runOnModule(llvm::Module&)
> lib/IR/LegacyPassManager.cpp:1567
> #9 0x2050014 in runOnModule lib/IR/LegacyPassManager.cpp:1625
>
> #10 0x2050014 in llvm::legacy::PassManagerImpl::run(llvm::Module&)
> lib/IR/LegacyPassManager.cpp:1734
> #11 0x685d57 in compileModule tools/llc/llc.cpp:356
>
> #12 0x685d57 in main tools/llc/llc.cpp:202
>
> #13 0x7fd3756f276c in __libc_start_main
> /build/buildd/eglibc-2.15/csu/libc-start.c:226
>
>
> On Wed, Apr 30, 2014 at 11:05 AM, Saleem Abdulrasool <
> compnerd at compnerd.org> wrote:
>
>> Author: compnerd
>> Date: Wed Apr 30 02:05:07 2014
>> New Revision: 207615
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=207615&view=rev
>> Log:
>> ARM: support stack probe emission for Windows on ARM
>>
>> This introduces the stack lowering emission of the stack probe function
>> for
>> Windows on ARM. The stack on Windows on ARM is a dynamically paged stack
>> where
>> any page allocation which crosses a page boundary of the following guard
>> page
>> will cause a page fault. This page fault must be handled by the kernel to
>> ensure that the page is faulted in. If this does not occur and a write
>> access
>> any memory beyond that, the page fault will go unserviced, resulting in an
>> abnormal program termination.
>>
>> The watermark for the stack probe appears to be at 4080 bytes (for
>> accommodating the stack guard canaries and stack alignment) when SSP is
>> enabled. Otherwise, the stack probe is emitted on the page size boundary
>> of
>> 4096 bytes.
>>
>> Added:
>> llvm/trunk/test/CodeGen/ARM/Windows/chkstk.ll
>> Modified:
>> llvm/trunk/docs/Extensions.rst
>> llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp
>>
>> Modified: llvm/trunk/docs/Extensions.rst
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/Extensions.rst?rev=207615&r1=207614&r2=207615&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/docs/Extensions.rst (original)
>> +++ llvm/trunk/docs/Extensions.rst Wed Apr 30 02:05:07 2014
>> @@ -159,3 +159,34 @@ different COMDATs:
>> .globl Symbol2
>> Symbol2:
>> .long 1
>> +
>> +Target Specific Behaviour
>> +=========================
>> +
>> +Windows on ARM
>> +--------------
>> +
>> +Stack Probe Emission
>> +^^^^^^^^^^^^^^^^^^^^
>> +
>> +The reference implementation (Microsoft Visual Studio 2012) emits stack
>> probes
>> +in the following fashion:
>> +
>> +.. code-block:: gas
>> +
>> + movw r4, #constant
>> + bl __chkstk
>> + sub.w sp, sp, r4
>> +
>> +However, this has the limitation of 32 MiB (±16MiB). In order to
>> accomodate
>> +larger binaries, LLVM supports the use of ``-mcode-model=large`` to
>> allow a 4GiB
>> +range via a slight deviation. It will generate an indirect jump as
>> follows:
>> +
>> +.. code-block:: gas
>> +
>> + movw r4, #constant
>> + movw r12, :lower16:__chkstk
>> + movt r12, :upper16:__chkstk
>> + blx r12
>> + sub.w sp, sp, r4
>> +
>>
>> Modified: llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp?rev=207615&r1=207614&r2=207615&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp (original)
>> +++ llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp Wed Apr 30 02:05:07
>> 2014
>> @@ -25,6 +25,7 @@
>> #include "llvm/CodeGen/RegisterScavenging.h"
>> #include "llvm/IR/CallingConv.h"
>> #include "llvm/IR/Function.h"
>> +#include "llvm/IR/Module.h"
>> #include "llvm/MC/MCContext.h"
>> #include "llvm/Support/CommandLine.h"
>> #include "llvm/Target/TargetOptions.h"
>> @@ -142,6 +143,14 @@ static int sizeOfSPAdjustment(const Mach
>> return count;
>> }
>>
>> +static bool WindowsRequiresStackProbe(const MachineFunction &MF,
>> + size_t StackSizeInBytes) {
>> + const MachineFrameInfo *MFI = MF.getFrameInfo();
>> + if (MFI->getStackProtectorIndex() > 0)
>> + return StackSizeInBytes >= 4080;
>> + return StackSizeInBytes >= 4096;
>> +}
>> +
>> void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
>> MachineBasicBlock &MBB = MF.front();
>> MachineBasicBlock::iterator MBBI = MBB.begin();
>> @@ -149,15 +158,16 @@ void ARMFrameLowering::emitPrologue(Mach
>> ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
>> MachineModuleInfo &MMI = MF.getMMI();
>> MCContext &Context = MMI.getContext();
>> + const TargetMachine &TM = MF.getTarget();
>> const MCRegisterInfo *MRI = Context.getRegisterInfo();
>> const ARMBaseRegisterInfo *RegInfo =
>> - static_cast<const
>> ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
>> + static_cast<const ARMBaseRegisterInfo*>(TM.getRegisterInfo());
>> const ARMBaseInstrInfo &TII =
>> - *static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
>> + *static_cast<const ARMBaseInstrInfo*>(TM.getInstrInfo());
>> assert(!AFI->isThumb1OnlyFunction() &&
>> "This emitPrologue does not support Thumb1!");
>> bool isARM = !AFI->isThumbFunction();
>> - unsigned Align =
>> MF.getTarget().getFrameLowering()->getStackAlignment();
>> + unsigned Align = TM.getFrameLowering()->getStackAlignment();
>> unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align);
>> unsigned NumBytes = MFI->getStackSize();
>> const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
>> @@ -187,7 +197,8 @@ void ARMFrameLowering::emitPrologue(Mach
>> .addCFIIndex(CFIIndex);
>> }
>>
>> - if (!AFI->hasStackFrame()) {
>> + if (!AFI->hasStackFrame() &&
>> + (!STI.isTargetWindows() || !WindowsRequiresStackProbe(MF,
>> NumBytes))) {
>> if (NumBytes - ArgRegsSaveSize != 0) {
>> emitSPUpdate(isARM, MBB, MBBI, dl, TII, -(NumBytes -
>> ArgRegsSaveSize),
>> MachineInstr::FrameSetup);
>> @@ -284,6 +295,50 @@ void ARMFrameLowering::emitPrologue(Mach
>> } else
>> NumBytes = DPRCSOffset;
>>
>> + if (STI.isTargetWindows() && WindowsRequiresStackProbe(MF, NumBytes)) {
>> + uint32_t NumWords = NumBytes >> 2;
>> +
>> + if (NumWords < 65536)
>> + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16),
>> ARM::R4)
>> + .addImm(NumWords));
>> + else
>> + BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R4)
>> + .addImm(NumWords);
>> +
>> + switch (TM.getCodeModel()) {
>> + case CodeModel::Small:
>> + case CodeModel::Medium:
>> + case CodeModel::Default:
>> + case CodeModel::Kernel:
>> + BuildMI(MBB, MBBI, dl, TII.get(ARM::tBL))
>> + .addImm((unsigned)ARMCC::AL).addReg(0)
>> + .addExternalSymbol("__chkstk")
>> + .addReg(ARM::R4, RegState::Implicit);
>> + break;
>> + case CodeModel::Large:
>> + case CodeModel::JITDefault: {
>> + LLVMContext &Ctx = MF.getMMI().getModule()->getContext();
>> + const GlobalValue *F =
>> + Function::Create(FunctionType::get(Type::getVoidTy(Ctx), false),
>> + GlobalValue::AvailableExternallyLinkage,
>> "__chkstk");
>> +
>> + BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R12)
>> + .addGlobalAddress(F);
>> + BuildMI(MBB, MBBI, dl, TII.get(ARM::BLX))
>> + .addReg(ARM::R12, RegState::Kill)
>> + .addReg(ARM::R4, RegState::Implicit);
>> + break;
>> + }
>> + }
>> +
>> + AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
>> TII.get(ARM::t2SUBrr),
>> + ARM::SP)
>> + .addReg(ARM::SP, RegState::Define)
>> + .addReg(ARM::R4, RegState::Kill)
>> + .setMIFlags(MachineInstr::FrameSetup)));
>> + NumBytes = 0;
>> + }
>> +
>> unsigned adjustedGPRCS1Size = GPRCS1Size;
>> if (NumBytes) {
>> // Adjust SP after all the callee-save spills.
>>
>> Added: llvm/trunk/test/CodeGen/ARM/Windows/chkstk.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/Windows/chkstk.ll?rev=207615&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/test/CodeGen/ARM/Windows/chkstk.ll (added)
>> +++ llvm/trunk/test/CodeGen/ARM/Windows/chkstk.ll Wed Apr 30 02:05:07 2014
>> @@ -0,0 +1,24 @@
>> +; RUN: llc -mtriple=thumbv7-windows -mcpu=cortex-a9 %s -o - \
>> +; RUN: | FileCheck -check-prefix CHECK-DEFAULT-CODE-MODEL %s
>> +
>> +; RUN: llc -mtriple=thumbv7-windows -mcpu=cortex-a9 -code-model=large %s
>> -o - \
>> +; RUN: | FileCheck -check-prefix CHECK-LARGE-CODE-MODEL %s
>> +
>> +define arm_aapcs_vfpcc void @check_watermark() {
>> +entry:
>> + %buffer = alloca [4096 x i8], align 1
>> + ret void
>> +}
>> +
>> +; CHECK-DEFAULT-CODE-MODEL: check_watermark:
>> +; CHECK-DEFAULT-CODE-MODEL: movw r4, #1024
>> +; CHECK-DEFAULT-CODE-MODEL: bl __chkstk
>> +; CHECK-DEFAULT-CODE-MODEL: sub.w sp, sp, r4
>> +
>> +; CHECK-LARGE-CODE-MODEL: check_watermark:
>> +; CHECK-LARGE-CODE-MODEL: movw r4, #1024
>> +; CHECK-LARGE-CODE-MODEL: movw r12, :lower16:__chkstk
>> +; CHECK-LARGE-CODE-MODEL: movt r12, :upper16:__chkstk
>> +; CHECK-LARGE-CODE-MODEL: blx r12
>> +; CHECK-LARGE-CODE-MODEL: sub.w sp, sp, r4
>> +
>>
>>
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>>
>
>
--
Saleem Abdulrasool
compnerd (at) compnerd (dot) org
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