[PATCH] D29765: Handle link of NoDebug CU with a CU that has debug emission enabled

[Teresa Johnson via Phabricator via llvm-commits]

tejohnson added inline comments.


================
Comment at: lib/CodeGen/LexicalScopes.cpp:82
+      // Ignore locations linked from a NoDebug compile unit.
+      auto *SP = dyn_cast<DISubprogram>(MIDL->getScope());
+      if (SP && SP->getUnit()->getEmissionKind() == DICompileUnit::NoDebug) {
----------------
dblaikie wrote:
> This probably won't catch all cases - if the location was in a subscope within the function (eg: try adding a {} to the function which should add an extra scope). Walking the scope chain until a DISubprogram is probably needed here - I forget if we have a nice wrapped up utility for that. Don't see one at a glance.
> 
> It should be an invariant/guaranteed that a DISubprogram is reached (& is the end of the scope chain), so something like:
> 
> oh, wait, no, here it is: http://llvm.org/docs/doxygen/html/classllvm_1_1DILocalScope.html#a747dd1690fc477a8d9638fa37a30ced8
> 
> so, I think, maybe:
> 
>   if (cast<DILocalScope>(MIDL->getScope())->getSubprogram()->getUnit()->getEmissionKind() == DICompileUnit::NoDebug) {
>     ...
I had just found the DILocalScope::getSubprogram() helper, since I was still getting the original seg fault when I tried the original failing internal code with this change. So now I have:

      // Ignore locations linked from a NoDebug compile unit.
      auto *SP = MIDL->getScope()->getSubprogram();
      if (SP->getUnit()->getEmissionKind() == DICompileUnit::NoDebug) {
        PrevMI = &MInsn;
        continue;
      }

(Don't need to cast MIDL->getScope() since it returns a DILocalScope). But I am *still* getting the original seg fault. Any idea what else I could be missing?


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Comment at: test/DebugInfo/Generic/debug_and_nodebug_CUs.ll:4
+
+; RUN: llc %s -o - | FileCheck %s
+; CHECK-DAG: # debug.c:
----------------
dblaikie wrote:
> Include the steps for reproducing this test case (basically the RUN lines, and the original C source/steps for producing the IR, from the first version of the test) - helps to visualize/document/reproduce the situation.
Will do


https://reviews.llvm.org/D29765