Fix an assertion of This DIE should've already been constructed when the " "definition DIE was created in " "getOrCreateSubprogramDIE

[yunlian]

Summary

This makes the assertion in PR37255 disappear.

[dblaikie]

Hi there :)

Just a note: There's no need to file a bug if you're already working on the
fix anyway. It's probably easier/quicker to provide all the context in the
patch/review rather than referring to a bug anyway.

This change will need a test case - and the test case might help explain
why/whether or not this is necessary/what's happening here & whether this
is the right approach to address it.

[yunlian]

It looks like this error comes from the mixing of LTO, debug fission and -fdebug-info-for-profiling.

In
DwarfCompileUnit::constructAbstractSubprogramScopeDIE, we would not run
getOrCreateSubprogramDIE if includeMinimalInlineScopes() returns True.

In DwarfUnit::applySubprogramAttributes, we would run
DwarfUnit::applySubprogramDefinitionAttributes if includeMinimalInlineScopes() returns False or -fdebug-info-for-profiling is set.

In my case, includeMinimalInlineScopes returns True and -fdebug-info-for-profiling is set. So it did not call getOrCreateSubprogramDIE
but it calls DwarfUnit::applySubprogramDefinitionAttributes to trigger the assertion.

[dblaikie]

Thanks for explaining - that sounds broadly right. Could you include a
minimal test case for this situation? You shouldn't need to involve LTO in
the test case itself - two (say, C or C++) source files compiled to IR,
llvm-link'd together & then the test case should probably be running llc on
that IR file. You can see other test cases for debug info in the
test/DebugInfo directory of LLVM's source.

[JDevlieghere]

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

1015

Can you please run clang-format over your change?

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

void DwarfCompileUnit::constructAbstractSubprogramScopeDIE(
   if (AbsDef)
     return;
 
   auto *SP = cast<DISubprogram>(Scope->getScopeNode());
 
   DIE *ContextDIE;
   DwarfCompileUnit *ContextCU = this;
 
-  if (includeMinimalInlineScopes())
+  if (includeMinimalInlineScopes()) {
     ContextDIE = &getUnitDie();
+    if (auto *SPDecl = SP->getDeclaration())
+      getOrCreateSubprogramDIE(SPDecl);
+  }
   // Some of this is duplicated from DwarfUnit::getOrCreateSubprogramDIE, with
   // the important distinction that the debug node is not associated with the
   // DIE (since the debug node will be associated with the concrete DIE, if
   // any). It could be refactored to some common utility function.
   else if (auto *SPDecl = SP->getDeclaration()) {
     ContextDIE = &getUnitDie();
     getOrCreateSubprogramDIE(SPDecl);
   } else {

 
 bool DwarfCompileUnit::isDwoUnit() const {
   return DD->useSplitDwarf() && Skeleton;
 }
 
 bool DwarfCompileUnit::includeMinimalInlineScopes() const {
   return getCUNode()->getEmissionKind() == DICompileUnit::LineTablesOnly ||
          (DD->useSplitDwarf() && !Skeleton);
 }