[llvm] r228748 - X86: Make @llvm.frameaddress work correctly with Windows unwind codes
David Majnemer
david.majnemer at gmail.com
Tue Apr 28 17:04:34 PDT 2015
On Tue, Apr 28, 2015 at 7:56 PM, Justin Bogner <mail at justinbogner.com>
wrote:
> David Majnemer <david.majnemer at gmail.com> writes:
> > On Mon, Apr 27, 2015 at 6:30 PM, Justin Bogner <mail at justinbogner.com>
> wrote:
> >
> > David Majnemer <david.majnemer at gmail.com> writes:
> > > Author: majnemer
> > > Date: Tue Feb 10 15:22:05 2015
> > > New Revision: 228748
> > >
> > > URL: http://llvm.org/viewvc/llvm-project?rev=228748&view=rev
> > > Log:
> > > X86: Make @llvm.frameaddress work correctly with Windows unwind
> codes
> > >
> > > Simply loading or storing the frame pointer is not sufficient for
> > > Windows targets. Instead, create a synthetic frame object that we
> will
> > > lower later. References to this synthetic object will be replaced
> with
> > > the correct reference to the frame address.
> > >
> > > Modified:
> > > llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
> > > llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
> > > llvm/trunk/lib/Target/X86/X86MachineFunctionInfo.h
> > > llvm/trunk/test/CodeGen/X86/frameallocate.ll
> > >
> > > Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
> > > URL:
> > > http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/
> > X86FrameLowering.cpp?rev=228748&r1=228747&r2=228748&view=diff
> > >
> ========================================================================
> > ======
> > > --- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
> > > +++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Tue Feb 10
> 15:22:05
> > 2015
> > > @@ -1242,6 +1242,9 @@ int X86FrameLowering::getFrameIndexOffse
> > > NumBytes = FrameSize - CSSize;
> > > }
> > > uint64_t SEHFrameOffset = calculateSetFPREG(NumBytes);
> > > + if (FI && FI == X86FI->getFAIndex())
> > > + return -SEHFrameOffset;
> > > +
> > > // FPDelta is the offset from the "traditional" FP location
> of the
> > old base
> > > // pointer followed by return address and the location
> required by
> > the
> > > // restricted Win64 prologue.
> > >
> > > Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
> > > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/
> > X86ISelLowering.cpp?rev=228748&r1=228747&r2=228748&view=diff
> > >
> ========================================================================
> > ======
> > > --- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
> > > +++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Tue Feb 10
> 15:22:05
> > 2015
> > > @@ -17953,15 +17953,33 @@ SDValue X86TargetLowering::LowerRETURNAD
> > > }
> > >
> > > SDValue X86TargetLowering::LowerFRAMEADDR(SDValue Op,
> SelectionDAG &
> > DAG) const {
> > > - MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
> > > + MachineFunction &MF = DAG.getMachineFunction();
> > > + MachineFrameInfo *MFI = MF.getFrameInfo();
> > > + X86MachineFunctionInfo *FuncInfo =
> MF.getInfo<X86MachineFunctionInfo>
> > ();
> > > + const X86RegisterInfo *RegInfo = Subtarget->getRegisterInfo();
> > > + EVT VT = Op.getValueType();
> > > +
> > > MFI->setFrameAddressIsTaken(true);
> > >
> > > - EVT VT = Op.getValueType();
> > > + if (MF.getTarget().getMCAsmInfo()->usesWindowsCFI()) {
> > > + // Depth > 0 makes no sense on targets which use Windows
> unwind
> > codes. It
> > > + // is not possible to crawl up the stack without looking at
> the
> > unwind codes
> > > + // simultaneously.
> > > + int FrameAddrIndex = FuncInfo->getFAIndex();
> > > + if (!FrameAddrIndex) {
> > > + // Set up a frame object for the return address.
> > > + unsigned SlotSize = RegInfo->getSlotSize();
> > > + FrameAddrIndex = MF.getFrameInfo()->CreateFixedObject(
> > > + SlotSize, /*Offset=*/INT64_MIN, /*IsImmutable=*/false);
> >
> > Sorry to dig up an old thread, but I was playing around with ubsan
> and
> > it looks like this causes some undefined behaviour. I guess we set
> the
> > Offset to INT64_MIN here as a dummy value, and it isn't intended to
> be
> > used, but later, in PrologEpilogInserter.cpp, we hit this logic in
> > PEI::calculateFrameObjectOffsets:
> >
> > if (StackGrowsDown) {
> > // The maximum distance from the stack pointer is at lower
> address of
> > // the object -- which is given by offset. For down growing stack
> > // the offset is negative, so we negate the offset to get the
> > distance.
> > FixedOff = -MFI->getObjectOffset(i);
> >
> > Here, when MFI->getObjectOffset returns INT64_MIN and we negate it,
> we
> > can't represent the result and thus hit undefined behaviour. It looks
> > like the effect is mostly harmless in practice, but...
> >
> > I guess that 0 is a better dummy value here - all tests continue to
> pass
> > if I change INT64_MIN to 0, anyway.
> >
> > WDYT?
> >
> > Could we do INT64_MIN+1?
>
> I don't see why not. Is there any particular reason that's better than
> 0? I guess just to make it obvious that it's special?
>
Yep, pretty much.
>
> >
> > > + FuncInfo->setFAIndex(FrameAddrIndex);
> > > + }
> > > + return DAG.getFrameIndex(FrameAddrIndex, VT);
> > > + }
> > > +
> > > + unsigned FrameReg =
> > > + RegInfo->getPtrSizedFrameRegister(DAG.getMachineFunction());
> > > SDLoc dl(Op); // FIXME probably not meaningful
> > > unsigned Depth =
> cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue
> > ();
> > > - const X86RegisterInfo *RegInfo = Subtarget->getRegisterInfo();
> > > - unsigned FrameReg = RegInfo->getPtrSizedFrameRegister(
> > > - DAG.getMachineFunction());
> > > assert(((FrameReg == X86::RBP && VT == MVT::i64) ||
> > > (FrameReg == X86::EBP && VT == MVT::i32)) &&
> > > "Invalid Frame Register!");
> > >
> > > Modified: llvm/trunk/lib/Target/X86/X86MachineFunctionInfo.h
> > > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/
> > X86MachineFunctionInfo.h?rev=228748&r1=228747&r2=228748&view=diff
> > >
> ========================================================================
> > ======
> > > --- llvm/trunk/lib/Target/X86/X86MachineFunctionInfo.h (original)
> > > +++ llvm/trunk/lib/Target/X86/X86MachineFunctionInfo.h Tue Feb 10
> > 15:22:05 2015
> > > @@ -50,6 +50,9 @@ class X86MachineFunctionInfo : public Ma
> > > /// ReturnAddrIndex - FrameIndex for return slot.
> > > int ReturnAddrIndex;
> > >
> > > + /// \brief FrameIndex for return slot.
> > > + int FrameAddrIndex;
> > > +
> > > /// TailCallReturnAddrDelta - The number of bytes by which
> return
> > address
> > > /// stack slot is moved as the result of tail call optimization.
> > > int TailCallReturnAddrDelta;
> > > @@ -92,6 +95,7 @@ public:
> > > CalleeSavedFrameSize(0),
> > > BytesToPopOnReturn(0),
> > > ReturnAddrIndex(0),
> > > + FrameAddrIndex(0),
> > > TailCallReturnAddrDelta(0),
> > > SRetReturnReg(0),
> > > GlobalBaseReg(0),
> > > @@ -109,6 +113,7 @@ public:
> > > CalleeSavedFrameSize(0),
> > > BytesToPopOnReturn(0),
> > > ReturnAddrIndex(0),
> > > + FrameAddrIndex(0),
> > > TailCallReturnAddrDelta(0),
> > > SRetReturnReg(0),
> > > GlobalBaseReg(0),
> > > @@ -139,6 +144,9 @@ public:
> > > int getRAIndex() const { return ReturnAddrIndex; }
> > > void setRAIndex(int Index) { ReturnAddrIndex = Index; }
> > >
> > > + int getFAIndex() const { return FrameAddrIndex; }
> > > + void setFAIndex(int Index) { FrameAddrIndex = Index; }
> > > +
> > > int getTCReturnAddrDelta() const { return
> TailCallReturnAddrDelta; }
> > > void setTCReturnAddrDelta(int delta) {TailCallReturnAddrDelta =
> > delta;}
> > >
> > >
> > > Modified: llvm/trunk/test/CodeGen/X86/frameallocate.ll
> > > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/
> > frameallocate.ll?rev=228748&r1=228747&r2=228748&view=diff
> > >
> ========================================================================
> > ======
> > > --- llvm/trunk/test/CodeGen/X86/frameallocate.ll (original)
> > > +++ llvm/trunk/test/CodeGen/X86/frameallocate.ll Tue Feb 10
> 15:22:05
> > 2015
> > > @@ -32,8 +32,12 @@ define void @alloc_func(i32* %s, i32* %d
> > > }
> > >
> > > ; CHECK-LABEL: alloc_func:
> > > +; CHECK: subq $48, %rsp
> > > +; CHECK: .seh_stackalloc 48
> > > +; CHECK: leaq 48(%rsp), %rbp
> > > +; CHECK: .seh_setframe 5, 48
> > > ; CHECK: .Lframeallocation_alloc_func = -[[offs:[0-9]+]]
> > > ; CHECK: movl $42, -[[offs]](%rbp)
> > > -; CHECK: movq %rbp, %rcx
> > > +; CHECK: leaq -48(%rbp), %rcx
> > > ; CHECK: callq print_framealloc_from_fp
> > > ; CHECK: retq
> > >
> > >
> > > _______________________________________________
> > > llvm-commits mailing list
> > > llvm-commits at cs.uiuc.edu
> > > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
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