[llvm] [LoopSafety] Cache whether block is guaranteed to execute (NFC) (PR #217943)

[Eli Friedman via llvm-commits]

================
@@ -204,6 +204,14 @@ bool LoopSafetyInfo::allLoopPathsLeadToBlock(const Loop *CurLoop,
   if (BB == CurLoop->getHeader())
     return true;
 
+  auto [It, Inserted] = GuaranteedToExecute.try_emplace(BB, false);
+  if (Inserted)
+    It->second = allLoopPathsLeadToBlockImpl(CurLoop, BB, DT);
----------------
efriedma-quic wrote:

Would it make sense to rework the algorithm to walk the whole loop once?

I guess we can leave that for a followup if it's still hot.

https://github.com/llvm/llvm-project/pull/217943