[llvm] [UndefOrPoison] [CompileTime] Avoid IDom walk unless required. NFC (PR #90092)

[via llvm-commits]

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@@ -7283,31 +7283,35 @@ static bool isGuaranteedNotToBeUndefOrPoison(
   // BB1:
   //   CtxI ; V cannot be undef or poison here
   auto *Dominator = DNode->getIDom();
-  while (Dominator) {
-    auto *TI = Dominator->getBlock()->getTerminator();
-
-    Value *Cond = nullptr;
-    if (auto BI = dyn_cast_or_null<BranchInst>(TI)) {
-      if (BI->isConditional())
-        Cond = BI->getCondition();
-    } else if (auto SI = dyn_cast_or_null<SwitchInst>(TI)) {
-      Cond = SI->getCondition();
-    }
+  // This check is purely for compile time reasons: we do not need to do the
+  // IDom walk if we are checking for only undef and the value is not a boolean.
+  if (includesPoison(Kind) || V->getType()->isIntOrIntVectorTy(1))
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annamthomas wrote:

That's right, thanks! it should broader the impact of this change as well. Will update the commit message. 

https://github.com/llvm/llvm-project/pull/90092