llvm dev - Nov 2016 - DWARF gotchas moving from 3.7.1 to 3.9.0

I recently upgraded a codebase to use LLVM 3.9.0, up from 3.7.1.

All seems to work well, except that I am unable to generate debug
information.

However, if I run objdump -g on the generated object file, it reports that
the compile unit has no children:

Contents of the .debug_abbrev section:

  Number TAG (0x0)
   1      DW_TAG_compile_unit    [no children]
    DW_AT_producer     DW_FORM_strp
    DW_AT_language     DW_FORM_data2
    DW_AT_name         DW_FORM_strp
    DW_AT_stmt_list    DW_FORM_sec_offset
    DW_AT value: 0     DW_FORM value: 0

The IR generated for 3.9.0 passes the IR verifier without complaint
(including the debug into verifier). I can run llc manually on my IR
without complaint. However, I am not able to ascertain whether llc runs the
debug info verifier by default.

One of the changes I had to make to get my code to compile was to remove
the function argument (of Function* type) from the call to
DIBuilder::createFunction(). This appears to be my problem, as my functions
do not appear to have debug info:
>From my 3.7.1 code:
define void @func(%artype*) #4 !dbg !5 {
!5 = distinct !DISubprogram(n...)
>From 3.9.0:
define void @func(%artype*) #4 {

What must I do to attach the DISubprogram metadata node to my Function,
assuming this is the problem?
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(+Adrian who might have some more context here)

Generally I'd suggest looking at Clang's code to see how it's
constructing
the correct IR - I'm not aware of any particular changes in the timeline
after we switched the subprogram edges (which it looks like we had already
done in 3.7, judging by the IR  you quoted)... don't have great guesses
here.

On Thu, Nov 17, 2016 at 6:46 PM David Jones via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> I recently upgraded a codebase to use LLVM 3.9.0, up from 3.7.1.
>
> All seems to work well, except that I am unable to generate debug
> information.
>
> However, if I run objdump -g on the generated object file, it reports that
> the compile unit has no children:
>
> Contents of the .debug_abbrev section:
>
>   Number TAG (0x0)
>    1      DW_TAG_compile_unit    [no children]
>     DW_AT_producer     DW_FORM_strp
>     DW_AT_language     DW_FORM_data2
>     DW_AT_name         DW_FORM_strp
>     DW_AT_stmt_list    DW_FORM_sec_offset
>     DW_AT value: 0     DW_FORM value: 0
>
> The IR generated for 3.9.0 passes the IR verifier without complaint
> (including the debug into verifier). I can run llc manually on my IR
> without complaint. However, I am not able to ascertain whether llc runs the
> debug info verifier by default.
>
> One of the changes I had to make to get my code to compile was to remove
> the function argument (of Function* type) from the call to
> DIBuilder::createFunction(). This appears to be my problem, as my functions
> do not appear to have debug info:
>
> From my 3.7.1 code:
>
> define void @func(%artype*) #4 !dbg !5 {
> !5 = distinct !DISubprogram(n...)
>
> From 3.9.0:
>
> define void @func(%artype*) #4 {
>
> What must I do to attach the DISubprogram metadata node to my Function,
> assuming this is the problem?
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Are you perhaps not calling

 void Function::setSubprogram (DISubprogram * SP)

http://llvm.org/doxygen/classllvm_1_1Function.html#a05a19abc8ee11d5909275d980efa1670
?

-- adrian
> On Nov 18, 2016, at 8:46 AM, David Blaikie <dblaikie at gmail.com>
wrote:
> 
> (+Adrian who might have some more context here)
> 
> Generally I'd suggest looking at Clang's code to see how it's
constructing the correct IR - I'm not aware of any particular changes in the
timeline after we switched the subprogram edges (which it looks like we had
already done in 3.7, judging by the IR  you quoted)... don't have great
guesses here.
> 
> On Thu, Nov 17, 2016 at 6:46 PM David Jones via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> I recently upgraded a codebase to use LLVM 3.9.0, up from 3.7.1.
> 
> All seems to work well, except that I am unable to generate debug
information.
> 
> However, if I run objdump -g on the generated object file, it reports that
the compile unit has no children:
> 
> Contents of the .debug_abbrev section:
> 
>   Number TAG (0x0)
>    1      DW_TAG_compile_unit    [no children]
>     DW_AT_producer     DW_FORM_strp
>     DW_AT_language     DW_FORM_data2
>     DW_AT_name         DW_FORM_strp
>     DW_AT_stmt_list    DW_FORM_sec_offset
>     DW_AT value: 0     DW_FORM value: 0
> 
> The IR generated for 3.9.0 passes the IR verifier without complaint
(including the debug into verifier). I can run llc manually on my IR without
complaint. However, I am not able to ascertain whether llc runs the debug info
verifier by default.
> 
> One of the changes I had to make to get my code to compile was to remove
the function argument (of Function* type) from the call to
DIBuilder::createFunction(). This appears to be my problem, as my functions do
not appear to have debug info:
> 
> From my 3.7.1 code:
> 
> define void @func(%artype*) #4 !dbg !5 {
> !5 = distinct !DISubprogram(n...)
> 
> From 3.9.0:
> 
> define void @func(%artype*) #4 {
> 
> What must I do to attach the DISubprogram metadata node to my Function,
assuming this is the problem?
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev