[PATCH] D66942: [DebugInfo] LiveDebugValues: locations with different exprs should compare differently

[Jeremy Morse via Phabricator via llvm-commits]

jmorse marked an inline comment as done.
jmorse added a comment.

In D66942#1651751 <https://reviews.llvm.org/D66942#1651751>, @aprantl wrote:

> Is there a big drop in variable locations with this (i.e., an improvement in accuracy)?


Zero change in the total number of variables with locations; but the number of bytes they cover falls by 0.6% (from 46.8% of total to 46.2%, IIRC). Not a huge change, but that's a decent number of locations that were presumably wrong.



================
Comment at: lib/CodeGen/LiveDebugValues.cpp:196
+    /// The (potentially complex) expression applied to this location.
+    const DIExpression *Expr;
+
----------------
aprantl wrote:
> Do you need to store this here, or could you derive it from MI below?
It could be either; the comment on line 211 indicates past concern about repeatedly accessing MI when comparing VarLocs. I'll give both options a spin through an asan build of clang-3.4 to see if there's any real difference.


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