[LLVMbugs] [Bug 22780] New: Drop fake DW_TAG_expression

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Mar 3 16:59:11 PST 2015


http://llvm.org/bugs/show_bug.cgi?id=22780

            Bug ID: 22780
           Summary: Drop fake DW_TAG_expression
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: DebugInfo
          Assignee: dexonsmith at apple.com
          Reporter: dexonsmith at apple.com
                CC: aprantl at apple.com, dblaikie at gmail.com,
                    echristo at gmail.com, friss at apple.com,
                    llvmbugs at cs.uiuc.edu
            Blocks: 21432
    Classification: Unclassified

Now that we have a type hierarchy (from bug 22464), we don't need
`DW_TAG_expression` to discriminate DWARF expressions.  We can use
`Metadata::getMetadataID()` instead.

1. Change `MDExpression::getTag()` to return `0u` and fix any fallout.
2. Remove `dwarf::DW_TAG_expression`.
3. Change `MDExpression` to inherit directly from `MDNode` instead of
`DebugNode`.
4. Investigate having it inherit directly from `Metadata` -- expressions don't
need/use metadata operands, they're not referenced from `NamedMDNode` or
`!attachments`, and they have no need for distinct/temporary semantics.

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