LLVM Bugzilla is read-only and represents the historical archive of all LLVM issues filled before November 26, 2021. Use github to submit LLVM bugs

Bug 35338 - Clients of SelectionDAG::ReplaceAllUsesWith drop debug info, & are inconsistent
Summary: Clients of SelectionDAG::ReplaceAllUsesWith drop debug info, & are inconsistent
Status: NEW
Alias: None
Product: libraries
Classification: Unclassified
Component: Common Code Generator Code (show other bugs)
Version: trunk
Hardware: PC All
: P normal
Assignee: Vedant Kumar
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2017-11-16 16:29 PST by Vedant Kumar
Modified: 2018-11-08 09:37 PST (History)
10 users (show)

See Also:
Fixed By Commit(s):

Attachments
Rough patch to enforce "don't drop debug info" in CombineTo(). (1.32 KB, patch)
2017-11-17 13:49 PST, Vedant Kumar 		Details
Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description Vedant Kumar 2017-11-16 16:29:55 PST 
There are a few issues here:

- CombineTo() calls ReplaceAllUsesWith(), which calls transferDbgValues(). If we assert that debug line/value information is preserved after the RAUW in CombineTo(), a bunch of tests fail.

- Clients of transferDbgValues() pass it SDValues which are attached to SDNodes with invalidated debug info. It seems unfortunate that we'd even try to propagate invalid debug info.

- One overload of ReplaceAllUsesWith(From, To) requires From != To, but another doesn't. This is partly annoying, but may also be masking correctness issues.
Comment 1 Vedant Kumar 2017-11-17 13:49:29 PST 
Created attachment 19445 [details]
Rough patch to enforce "don't drop debug info" in CombineTo().

I've attached a rough patch which should enforce "don't drop debug info" in CombineTo(), in case anyone wants to poke around with it. I probably won't get to this until after Thanksgiving.