[all-commits] [llvm/llvm-project] ed940d: [DWARFLinker] Fix matching logic to remove type 1 ...

[Peter Rong via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ed940d7228aec95e994be848f1e42eab2a7fa7f3
      https://github.com/llvm/llvm-project/commit/ed940d7228aec95e994be848f1e42eab2a7fa7f3
  Author: Peter Rong <peterrong96 at gmail.com>
  Date:   2025-07-30 (Wed, 30 Jul 2025)

  Changed paths:
    M llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp
    M llvm/test/tools/dsymutil/ARM/stmt-seq-macho.test

  Log Message:
  -----------
  [DWARFLinker] Fix matching logic to remove type 1 missing offsets (#149618)

Second attempt to fix
https://discourse.llvm.org/t/rfc-new-dwarf-attribute-for-symbolication-of-merged-functions/79434/29?u=alx32

(First attempt: https://github.com/llvm/llvm-project/pull/143656)

Context: the sequence offset to row index we parsed may not be complete.
And we need to add manual matching to it.

https://github.com/llvm/llvm-project/pull/143656 attempts to do trivial
1:1 matching, however, sometimes they don't line up perfectly, as shown
below:
 
 ```
// While SeqOffToOrigRow parsed from CU could be the ground truth,
          // e.g.
          //
          // SeqOff     Row
          // 0x08        9
          // 0x14       15
          //
// The StmtAttrs and SeqStartRows may not match perfectly, e.g.
          //
          // StmtAttrs  SeqStartRows
          // 0x04        3
          // 0x08        5
          // 0x10        9
          // 0x12       11
          // 0x14       15
          //
// In this case, we don't want to assign 5 to 0x08, since we know 0x08
// maps to 9. If we do a dummy 1:1 mapping 0x10 will be mapped to 9
// which is incorrect. The expected behavior is ignore 5, realign the
          // table based on the result from the line table:
          //
          // StmtAttrs  SeqStartRows
          // 0x04        3
          //   --        5
          // 0x08        9 <- LineTableMapping ground truth
          // 0x10       11
          // 0x12       --
          // 0x14       15 <- LineTableMapping ground truth
 ```
 
In this case, we need to use the mapping we read from the line table as
a ground truth and organize them properly to prevent duplicated
offset/missing offset.
 
 Test:
 
 Updated the test case

---------

Signed-off-by: Peter Rong <PeterRong at meta.com>



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