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7e3735d1a1
Relative to the previous attempt, this adjusts isEscapeSource() to not treat calls with captures(ret: address, provenance) or similar arguments as escape sources. This addresses the miscompile reported at: https://github.com/llvm/llvm-project/pull/125880#issuecomment-2656632577 The implementation uses a helper function on CallBase to make this check a bit more efficient (e.g. by skipping the byval checks) as checking attributes on all arguments if fairly expensive. ------ This extends CaptureTracking to support inferring non-trivial CaptureInfos. The focus of this patch is to only support FunctionAttrs, other users of CaptureTracking will be updated in followups. The key API changes here are: * DetermineUseCaptureKind() now returns a UseCaptureInfo where the UseCC component specifies what is captured at that Use and the ResultCC component specifies what may be captured via the return value of the User. Usually only one or the other will be used (corresponding to previous MAY_CAPTURE or PASSTHROUGH results), but both may be set for call captures. * The CaptureTracking::captures() extension point is passed this UseCaptureInfo as well and then can decide what to do with it by returning an Action, which is one of: Stop: stop traversal. ContinueIgnoringReturn: continue traversal but don't follow the instruction return value. Continue: continue traversal and follow the instruction return value if it has additional CaptureComponents. For now, this patch retains the (unsound) special logic for comparison of null with a dereferenceable pointer. I'd like to switch key code to take advantage of address/address_is_null before dropping it. This PR mainly intends to introduce necessary API changes and basic inference support, there are various possible improvements marked with TODOs.