llvm-project

0e17fcf9 - [LifetimeSafety] Implement support for lifetimebound attribute (#158489)

[LifetimeSafety] Implement support for lifetimebound attribute (#158489) Add support for `lifetimebound` attributes in the lifetime safety analysis to track loans from function parameters to return values. Implemented support for `lifetimebound` attributes on function parameters This change replaces the single `AssignOriginFact` with two separate operations: `OriginFlowFact` and `KillOriginFact`. The key difference is in semantics: * Old `AssignOriginFact`: Replaced the destination origin's loans entirely with the source origin's loans. * New `OriginFlowFact`: Can now optionally merge the source origin's loans to the destination's existing loans. * New `KillOriginFact`: Clears all loans from an origin. For function calls with `lifetimebound` parameters, we kill the the return value' origin first then use `OriginFlowFact` to accumulate loans from multiple parameters into the return value's origin - enabling tracking multiple lifetimebound arguments. - Added a new `LifetimeAnnotations.h/cpp` to provide helper functions for inspecting and inferring lifetime annotations - Moved several functions from `CheckExprLifetime.cpp` to the new file to make them reusable The `lifetimebound` attribute is a key mechanism for expressing lifetime dependencies between function parameters and return values. This change enables the lifetime safety analysis to properly track these dependencies, allowing it to detect more potential dangling reference issues.