[LAA] Only invalidate loops that require runtime checks (NFCI).

LAA doesn't keep references to IR outside the loop or references to
SCEVs that may be invalidated, unless runtime checks are needed (either
memory or SCEV predicates). For the current LAA users, it should be
sufficient to invalidate entries for loops that require runtime checks,
thus avoiding analyzing loops again unnecessarily.

This helps reduce compile-time, in particular when removing the
restrictions added in 234cc40adc6.

https://llvm-compile-time-tracker.com/compare.php?from=73894dba2cdbcc00678d0c13a6b61765675f60b4&to=05c6bdc41b5f63696ebeb7116325725fa94f66d6&stat=instructions:u

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index f132e45..018861a 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -3084,6 +3084,22 @@ const LoopAccessInfo &LoopAccessInfoManager::getInfo(Loop &L) {
 
   return *It->second;
 }
+void LoopAccessInfoManager::clear() {
+  SmallVector<Loop *> ToRemove;
+  // Collect LoopAccessInfo entries that may keep references to IR outside the
+  // analyzed loop or SCEVs that may have been modified or invalidated. At the
+  // moment, that is loops requiring memory or SCEV runtime checks, as those cache
+  // SCEVs, e.g. for pointer expressions.
+  for (const auto &[L, LAI] : LoopAccessInfoMap) {
+    if (LAI->getRuntimePointerChecking()->getChecks().empty() &&
+        LAI->getPSE().getPredicate().isAlwaysTrue())
+      continue;
+    ToRemove.push_back(L);
+  }
+
+  for (Loop *L : ToRemove)
+    LoopAccessInfoMap.erase(L);
+}
 
 bool LoopAccessInfoManager::invalidate(
     Function &F, const PreservedAnalyses &PA,