[PATCH] D140900: [DebugInfo] Print empty MDTuples wrapped in MetadataAsValue inline

[Orlando Cazalet-Hyams via Phabricator via llvm-commits]

Orlando created this revision.
Orlando added reviewers: StephenTozer, jmorse, djtodoro, jryans, scott.linder.
Orlando added a project: debug-info.
Herald added a subscriber: hiraditya.
Herald added a project: All.
Orlando requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

This improves the readability of debugging intrinsics. Instead of:

  call void @llvm.dbg.value(metadata !2, ...)
  !2 = !{}

We will see:

  call void @llvm.dbg.value(metadata !{}, ...)
  !2 = !{}

Note that we still get a numbered metadata entry for the node even if it's not
used elsewhere. This is to avoid adding more context to the print functions.

This is already legal IR - LLVM can parse and understand it - so there is no
need to update the parser.

The next patches in this stack will make such empty metadata operands more
common and semantically important.

Related to https://discourse.llvm.org/t/auto-undef-debug-uses-of-a-deleted-value


https://reviews.llvm.org/D140900

Files:
  llvm/lib/IR/AsmWriter.cpp
  llvm/test/DebugInfo/Generic/empty-metadata-roundtrip.ll
  llvm/test/Transforms/GlobalOpt/localize-constexpr-debuginfo.ll
  llvm/test/Transforms/GlobalOpt/metadata.ll
  llvm/test/Transforms/LoopIdiom/debug-line.ll
  llvm/unittests/IR/MetadataTest.cpp

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