[llvm] [SimplifyIndVar] Push more users to worklist for simplifyUsers (PR #93598)

[Nikita Popov via llvm-commits]

================
@@ -854,16 +861,23 @@ static void pushIVUsers(
     if (UI == Def)
       continue;
 
-    // Only change the current Loop, do not change the other parts (e.g. other
-    // Loops).
-    if (!L->contains(UI))
+    // Avoid adding Defs that SCEV expand to themselves, e.g. the LoopPhis
+    // of the outter loops.
+    if (!DT->dominates(L->getHeader(), UI->getParent()))
       continue;
 
     // Do not push the same instruction more than once.
     if (!Simplified.insert(UI).second)
       continue;
 
-    SimpleIVUsers.push_back(std::make_pair(UI, Def));
+    unsigned Counter =
+        L->contains(UI)
+            ? 0 // reset depth if we go back inside the loop.
+            : OutOfLoopChainCounter + (UI->getParent() != Def->getParent());
----------------
nikic wrote:

Why is this a limit on the depth of the blocks rather than instructions? You can have a very long chain of instructions within a single block, or a very short one across blocks. It seems like that would be the more relevant quantity.

https://github.com/llvm/llvm-project/pull/93598