This patch extends the logic added in https://github.com/llvm/llvm-project/pull/128061 to support dereferenceability information from assumptions as well. Unfortunately both assumption cache and the dominator tree need to be threaded through multiple layers to make them available where needed. PR: https://github.com/llvm/llvm-project/pull/147047
Currently if there's any memory access that AccessAnalysis couldn't analyze then all of the runtime pointer check results are discarded. This patch makes this able to be controlled with the AllowPartial option, which makes it so we generate the runtime check information for those pointers that we could analyze, as transformations may still be able to make use of the partial information. Of the transformations that use LoopAccessAnalysis, only LoopVersioningLICM changes behaviour as a result of this change. This is because the others either: * Check canVectorizeMemory, which will return false when we have partial pointer information as analyzeLoop() will return false. * Examine the dependencies returned by getDepChecker(), which will be empty as we exit analyzeLoop if we have partial pointer information before calling areDepsSafe(), which is what fills in the dependency information.
Currently when we version a loop all loads and stores have the noalias metadata added to them. If there were some pointers that could not be analysed, and thus we could not generate runtime aliasing checks for, then we should not mark loads and stores using these pointers as noalias. This is done by getting rid of setNoAliasToLoop and instead using annotateLoopWithNoAlias, as that already correctly handles partial alias information. This does result in slightly different aliasing metadata being generated, but it looks like it's more precise. Currently this doesn't result in any change to the transforms that LoopVersioningLICM does, as LoopAccessAnalysis discards all results if it couldn't analyse every pointer leading to no loop versioning happening, but an upcoming patch will change that and we need this first otherwise we incorrectly mark some pointers as noalias even when they aren't.
Identified with misc-include-cleaner.
Following up to 933f49248, also update the code reasoning about backwards dependences to support non-constant distances. Update the code to use the signed minimum distance instead of a constant distance This means e checked the lower bound of the dependence distance and the distance may be larger at runtime (and safe for vectorization). Whether to classify it as Unknown or Backwards depends on the vector width and LAA was updated to take TTI to get the maximum vector register width. If the minimum dependence distance is larger than the max vector width, we consider it as backwards-vectorizable. Otherwise we classify them as Unknown, so we re-try with runtime checks. PR: https://github.com/llvm/llvm-project/pull/91525
This changes the AliasSetTracker to track memory locations instead of pointers in its alias sets. The motivation for this is outlined in an RFC posted on LLVM discourse: https://discourse.llvm.org/t/rfc-dont-merge-memory-locations-in-aliassettracker/73336 In the data structures of the AST implementation, I made the choice to replace the linked list of `PointerRec` entries (that had to go anyway) with a simple flat vector of `MemoryLocation` objects, but for the `AliasSet` objects referenced from a lookup table, I retained the mechanism of a linked list, reference counting, forwarding, etc. The data structures could be revised in a follow-up change.