[llvm-dev] llvm-link: Missing Dwarf DIE references

[Adrian Prantl via llvm-dev]

> On Sep 18, 2017, at 1:28 PM, Jack Carter via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> I am experiencing an issue combining bitcode files for the purpose of generating the combined bitcodes as a single bitcode file. I would like to have any pointers to help me debug this or maybe it has been seen before and a fix is either being worked on or is done.
> 
> I am using the Xcode 9.0 compiler. I believe the Swift code is 3.x. I have reproduced this using the tot llvm-link.

As general note, for questions about using the Swift compiler the swift-dev mailing list on swift.org is a more appropriate forum unless the bug can also be reproduced with an unmodified llvm.oprg toolchain.

> 
> The input modules are from Swift (LucidDreams) and have been compiled -O. The problem doesn't seem to exist when they are compiled -Onone. 
> 
> The llvm-link occurs without error and the subsequent compilation also seems to go fine, but when the resultant llvm-dwarfdump -verbose -verify is run I get a bunch of the following errors:
> 
> warning: could not find referenced DIE
>     in DIE:
> 
> 0x0000a33f:       DW_TAG_inlined_subroutine [20] *
>                     DW_AT_abstract_origin [DW_FORM_ref4]	(cu + 0x0c84 => {0x0000a40d})
>                     DW_AT_ranges [DW_FORM_sec_offset]	(0x00021960
>                        [0x0000000000001878 - 0x000000000000187c)
>                        [0x00000000000018b0 - 0x0000000000001910)
>                        [0x0000000000001980 - 0x00000000000019e0))
>                     DW_AT_call_file [DW_FORM_data1]	("<mypath>/testprogram_lucidDreams/iOS_APP/LucidDreams/DreamListViewControllerModel.swift")
>                     DW_AT_call_line [DW_FORM_data1]	(61)
> while processing <mypath>/testprogram_lucidDreams/iOS_APP/DerivedData/iOS_APP/Build/Intermediates.noindex/iOS_APP.build/Debug-iphoneos/iOS_APP.build/Objects-normal/arm64/iOS_APP.bc.o:
> 
> All the errors reference DreamListViewControllerModel.swift and have todo with inlining, but if I remove enough of the input bitcode objects from the llvm-link the error goes away even though DreamListViewControllerModel is still included.
> 
> Here are the commands I used to generate the error (omitting the original Swift compile):
> 
> ########################
> ########################
> llvm-link \
> -o <mypath>/iOS_APP.bc \
> <mypath>/DreamListViewController.o \
> <mypath>/TextEntryCollectionViewCell.bc \
> <mypath>/ImageDrawable.bc \
> <mypath>/DreamScene.bc \
> <mypath>/DreamListViewControllerModel.bc \
> <mypath>/CreatureCollectionViewCell.bc \
> <mypath>/RangeReplaceableCollection+IndexSet.bc \
> <mypath>/DreamPreviewHeaderReusableView.bc \
> <mypath>/Rendering.bc
> 
> ########################
> ########################
> xcrun \
> --sdk iphoneos \
> <mypath>/Xcode_9.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ \
> -fembed-bitcode \
> <mypath>/iOS_APP.bc \
> -arch arm64 \
> -O0 \
> -c \
> -o <mypath>/iOS_APP.bc.o
> 
> ########################
> ########################
> llvm-dwarfdump -verbose -verify small.o > small.o.dwarfdump
> 
> Any insights would be appreciated. Input bitcode files are attached.

Could you please file a bugreport on bugs.swift.org for this and assign it to me?

thanks,
adrian

> 
> Thanks,
> Jack
> <bitcode_files.tgz>
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