llvm-project

a8cb6c47 - [DebugInfo][DwarfDebug] Defer parent attachment of function-local DIEs until endModule() (#230866)

[DebugInfo][DwarfDebug] Defer parent attachment of function-local DIEs until endModule() (#230866) As it was discussed previously in https://github.com/llvm/llvm-project/pull/142166#issuecomment-2950057682, when DIEs for function-local types are emitted in DWARF, they should be placed in their corresponding abstract subprograms, or abstract lexical blocks inside them (if abstract DIE for subprogram exists). If a function-local entity DIE is emitted in `DwarfDebug::endFunctionImpl()`, DwarfDebug may not know yet if an abstract subprogram should be created for the scope of function-local entity, thus, function-local type may be wrongly placed (inside concrete subprogram DIE instead of abstract SP DIE, see https://github.com/llvm/llvm-project/issues/29985, https://github.com/llvm/llvm-project/issues/55680 ). Initially, to solve that for subprograms that represent fully inlined functions, LexicalScopes class was modified to build a map of subprograms attached to `llvm::Function`s, so that if it is known that a subprogram is fully inlined (not attached to any Function), i.e. it requires an abstract DIE, its abstract DIE can be created on demand https://github.com/llvm/llvm-project/pull/160786. This solved the problem for fully inlined subprograms, but the case of `llvm::Function`s that are not optimized out was still uncovered (https://github.com/llvm/llvm-project/issues/55680). Then, emission of retained local types was postponed to `DwarfDebug::endModule()` in https://github.com/llvm/llvm-project/pull/165032. By the moment of `DwarfDebug::endModule()` call, all necessary abstract DIEs should be emitted. However, when DIEs for local variables of a function-local type are emitted, local type DIE creation is still triggered inside `DwarfDebug::endFunctionImpl()` call The call chain is: `DwarfDebug::endFunctionImpl()` -> `TheCU.constructSubprogramScopeDIE()` -> `DwarfCompileUnit::createAndAddScopeChildren()` -> `DwarfCompileUnit::constructVariableDIE()` -> `DwarfCompileUnit::applyCommonDbgVariableAttributes()` -> `DwarfUnit::addType()`. Thus, function-local types may still be emitted into concrete subprogram DIEs instead of abstract ones. To fix the issue, when a DIE for a function-local entity is created prior to `DwarfDebug::endModule()` call, and an abstract DIE for its scope does not exist (but it may be created later), the function-local DIE is attached to a temporary parent DIE within the scope's CU. Later in `DwarfDebug::endModule()`, by the point when all abstract scope DIEs should be created, all such DIEs are reattached to their proper parents (abstract or concrete). Fixes https://github.com/llvm/llvm-project/issues/55680. Authored-By: Kristina Bessonova <kbessonova@accesssoftek.com>