[llvm-dev] CloneFunctionInto produces invalid debug info

[Sergei Larin via llvm-dev]

We are seeing the same. Cloning is failing to add newly created  DICompileUnit to llvm.dbg.cu in the module resulting in verifier assert.

 

Sergei

 

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Matthias Bernad via llvm-dev
Sent: Thursday, June 15, 2017 10:32 AM
To: llvm-dev at lists.llvm.org
Subject: [llvm-dev] CloneFunctionInto produces invalid debug info

 

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 llvm.dbg.cu <http://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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