[NFC] Leave a comment in Local.cpp about debug info & sample profiling

[mtrofin]

Issue #152767

[mtrofin]

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• [NFC] Leave a comment in Local.cpp about debug info & sample profiling #155296 👈 (View in Graphite)
• [IR] Add MD_prof to the Keep list of dropUBImplyingAttrsAndMetadata #154635
• [SimplfyCFG] Set MD_prof for select used for certain conditional simplifications #154426
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[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Mircea Trofin (mtrofin)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/155296.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Utils/Local.cpp (+5-2)

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index ac344904f90f0..821a58caf10b2 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -3342,8 +3342,11 @@ void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt,
   // retain their original debug locations (DILocations) and debug intrinsic
   // instructions.
   //
-  // Doing so would degrade the debugging experience and adversely affect the
-  // accuracy of profiling information.
+  // Doing so would degrade the debugging experience.
+  //
+  // FIXME: Issue #152767: debug info should also be the same as the
+  // original branch, **if** the user explicitly indicated that (for sampling
+  // PGO)
   //
   // Currently, when hoisting the instructions, we take the following actions:
   // - Remove their debug intrinsic instructions.

[mtrofin]

Found this in a drive-by, worth stamping it with the issue so it's easy to find it later.

[dwblaikie]

I've still got concerns about this direction/divergence between users and profilers & would love to see some attempt at unification - but a comment that points to the issue at least centralizes the discusison and leaves breadcrumbs towards it when it needs to be cleaned up in any direction later.