[DWARF] Line 0 should not have is_stmt set

[pogo59]

Bugzilla Link	34522
Version	trunk
OS	Windows NT
CC	@adrian-prantl,@dwblaikie

Extended Description

I think it does not make sense for a line-0 record to have is_stmt set.
I made a point of turning it off for implicit line-0 records generated
by DwarfDebug, and in real code I don't think we would ever see it.

However, adding an assertion to this effect broke 40 LLVM tests.
In most cases, the problem is merely that the test-input IR does
not specify everything that normal IR input has. In particular, at
some point DISubprogram started making a distinction between Line and
scopeLine, i.e. line of declaration versus where-the-code-starts.
If the scopeLine argument is missing from textual IR, it defaults to
zero, and that gets propagated to the entry point of the subprogram,
which is a stopping point and therefore has is_stmt=1.

Defaulting scopeLine to Line fixed 33 of the tests, and eyeballing
the other 7 suggests that most of them don't set Line either. This
is (IMO) a matter of flawed tests and it should be no sweat to fix.

There is one test related to prologue-end that seems to be testing
that it's okay for prologue-end to be line 0, and I ran out of time
to investigate any further.

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Assign the issue to you.
2. Fix the issue locally.
3. Run the test suite locally.
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   e.g. use make check-clang-ast to only run Clang's AST tests.
4. Create a git commit
5. Run git clang-format HEAD~1 to format your changes.
6. Submit the patch to Phabricator.
   6.1) Detailed instructions can be found here

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If you have any further questions about this issue, don't hesitate to ask via a comment on this Github issue.

@llvm/issue-subscribers-good-first-issue

[jimmy2683]

Hello Developers, I am interested in resolving this issue.

[llvmbot]

@llvm/issue-subscribers-debuginfo

Author: Paul T Robinson (pogo59)

| | | | --- | --- | | Bugzilla Link | [34522](https://llvm.org/bz34522) | | Version | trunk | | OS | Windows NT | | CC | @adrian-prantl,@dwblaikie |

Extended Description

I think it does not make sense for a line-0 record to have is_stmt set.
I made a point of turning it off for implicit line-0 records generated
by DwarfDebug, and in real code I don't think we would ever see it.

However, adding an assertion to this effect broke 40 LLVM tests.
In most cases, the problem is merely that the test-input IR does
not specify everything that normal IR input has. In particular, at
some point DISubprogram started making a distinction between Line and
scopeLine, i.e. line of declaration versus where-the-code-starts.
If the scopeLine argument is missing from textual IR, it defaults to
zero, and that gets propagated to the entry point of the subprogram,
which is a stopping point and therefore has is_stmt=1.

Defaulting scopeLine to Line fixed 33 of the tests, and eyeballing
the other 7 suggests that most of them don't set Line either. This
is (IMO) a matter of flawed tests and it should be no sweat to fix.

There is one test related to prologue-end that seems to be testing
that it's okay for prologue-end to be line 0, and I ran out of time
to investigate any further.

[OCHyams]

Hello Developers, I am interested in resolving this issue.

Please go ahead :)