[llvm-dev] CloneFunctionInto produces invalid debug info

Fri Jun 16 13:54:18 PDT 2017

Sorry. It takes a pass that was not accepted for upstreaming.. It uses
CloneFunctionInto with module level flag on. In the input IR there is a
strangely formed (but correct) debug info MD that causes duplication of
existing DICompileUnit during cloning, but llvm.dbg.cu is not updated. I got
around by a quick cleanup pass that detects the situation and simply adds
them in. Something like this:

  auto *CUs = F->getParent()->getNamedMetadata("llvm.dbg.cu");

  if (!CUs)

    return;

  SmallPtrSet<Metadata *, 2> Listed;

  Listed.insert(CUs->op_begin(), CUs->op_end());

  for (auto *CU : CUVisited)

    if (!Listed.count(CU)) {

      auto *Op = dyn_cast<MDNode>(CU);

      CUs->addOperand(Op);  <<<<<<<<<<<<<<<<<<<<<<<

    }

Sorry, I realize this is not much help.

Sergei

From: aprantl at apple.com [mailto:aprantl at apple.com] 
Sent: Thursday, June 15, 2017 5:25 PM
To: Sergei Larin <slarin at codeaurora.org>
Cc: Keno Fischer <keno at juliacomputing.com>; llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] CloneFunctionInto produces invalid debug info

Can you send me a patch with instructions to reproduce? I can take a look.

-- adrian

On Jun 15, 2017, at 2:23 PM, Sergei Larin <slarin at codeaurora.org
<mailto:slarin at codeaurora.org> > wrote:

Yes, it does for us. My tree is couple days off the tip, and I see it there.

Sergei

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Keno
Fischer via llvm-dev
Sent: Thursday, June 15, 2017 1:25 PM
To: Adrian Prantl <aprantl at apple.com <mailto:aprantl at apple.com> >
Cc: llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> >
Subject: Re: [llvm-dev] CloneFunctionInto produces invalid debug info

This all looks very similar to a bug in the cloning stuff I fixed recently,
so would be indeed good to know if this is still happening on master.

On Thu, Jun 15, 2017 at 2:23 PM, Adrian Prantl via llvm-dev <
<mailto:llvm-dev at lists.llvm.org> llvm-dev at lists.llvm.org> wrote:

If you are doing this work based off LLVM trunk, could you send me your
patch to reproduce the problem?

-- adrian

On Jun 15, 2017, at 8:31 AM, Matthias Bernad via llvm-dev <
<mailto:llvm-dev at lists.llvm.org> llvm-dev at lists.llvm.org> wrote:

Hi!

We are currently working on a science project and implemented a FunctionPass
that clones a function (more precisely a constructor of a struct/class) and
adds a parameter.

First, we create a new function with a new function type, which includes the
newly added parameter:

Function *NF = Function::Create(NewFTy, F.getLinkage(), F.getName() +
"Cloned", F.getParent());

and after setting up the ValueToValueMapTy, we use the CloneFunctionInto
method to clone the function body

CloneFunctionInto(NF, &F, Map, true, Returns, "Cloned");

The code seems to work as intended, but when we try to emit debug symbols
(clang -g flag) the pass fails with following message:

"All DICompileUnits must be listed in  <http://llvm.dbg.cu/> llvm.dbg.cu"

Nevertheless, we can dump the Module and therefore can print out the
annotated IR.

This is what the function to be cloned looks like:

; Function Attrs: noinline nounwind uwtable

define linkonce_odr void @_ZN12MyFunnyClassC2Ev(%struct.MyFunnyClass* %this)
unnamed_addr #4 comdat align 2 !dbg !46 {

entry:

  %this.addr = alloca %struct.MyFunnyClass*, align 8

  store %struct.MyFunnyClass* %this, %struct.MyFunnyClass** %this.addr,
align 8

  call void @llvm.dbg.declare(metadata %struct.MyFunnyClass** %this.addr,
metadata !49, metadata !31), !dbg !50

... rest of function code

}

!46 = distinct !DISubprogram(name: "MyFunnyClass", linkageName:
"_ZN12MyFunnyClassC2Ev", scope: !15, file: !1, line: 1, type: !25, isLocal:
false, isDefinition: true, scopeLine: 1, flags: DIFlagArtificial |
DIFlagPrototyped, isOptimized: false, unit: !0, declaration: !47, variables:
!2)

and the cloned function:

; Function Attrs: noinline nounwind uwtable

define linkonce_odr void @_ZN12MyFunnyClassC2EvCloned(%struct.MyFunnyClass*
%this, { [6 x i8*] }* %newparam) unnamed_addr #4 align 2 !dbg !73 {

entry:

  %this.addr = alloca %struct.MyFunnyClass*, align 8

  store %struct.MyFunnyClass* %this, %struct.MyFunnyClass** %this.addr,
align 8

  call void @llvm.dbg.declare(metadata %struct.MyFunnyClass** %this.addr,
metadata !89, metadata !31), !dbg !91

... rest of function code

}

!73 = distinct !DISubprogram(name: "MyFunnyClass", linkageName:
"_ZN12MyFunnyClassC2Ev", scope: !74, file: !1, line: 1, type: !81, isLocal:
false, isDefinition: true, scopeLine: 1, flags: DIFlagArtificial |
DIFlagPrototyped, isOptimized: false, unit: !87, declaration: !88,
variables: !2)

So the cloned function gets annotated with debug symbols as expected. We
noticed that the linkageName of the cloned function is the same as the
original one's. Could that cause the error mentioned above? If so, how can
we fix that error?

Best regards and thanks in advance,

Matthias

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