[PATCH] D44748: Track whether the size of a MemoryLocation is precise

[Nuno Lopes via Phabricator via llvm-commits]

nlopes added inline comments.


================
Comment at: lib/Analysis/MemoryDependenceAnalysis.cpp:1115
   if (!Pair.second) {
-    if (CacheInfo->Size < Loc.Size) {
-      // The query's Size is greater than the cached one. Throw out the
-      // cached data and proceed with the query at the greater size.
-      CacheInfo->Pair = BBSkipFirstBlockPair();
-      CacheInfo->Size = Loc.Size;
-      for (auto &Entry : CacheInfo->NonLocalDeps)
-        if (Instruction *Inst = Entry.getResult().getInst())
-          RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
-      CacheInfo->NonLocalDeps.clear();
-    } else if (CacheInfo->Size > Loc.Size) {
-      // This query's Size is less than the cached one. Conservatively restart
-      // the query using the greater size.
-      return getNonLocalPointerDepFromBB(
-          QueryInst, Pointer, Loc.getWithNewSize(CacheInfo->Size), isLoad,
-          StartBB, Result, Visited, SkipFirstBlock);
+    if (!CacheInfo->Size.equalsIgnoringPrecision(Loc.Size)) {
+      // For our purposes, unknown size > all others.
----------------
Why is it ok to ignore precision here?
If we did an alias query before with precise size, and the new one is with upper-bound, the results don't seem reusable.
(I have no clue how this function works; so I don't know if the above case can happen)


https://reviews.llvm.org/D44748