[llvm] [SLP] Match poison as instruction with the same opcode (PR #115946)

[Yingwei Zheng via llvm-commits]

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@@ -940,8 +952,17 @@ static InstructionsState getSameOpcode(ArrayRef<Value *> VL,
     if (!isTriviallyVectorizable(BaseID) && BaseMappings.empty())
       return InstructionsState::invalid();
   }
+  bool AnyPoison = InstCnt != VL.size();
   for (int Cnt = 0, E = VL.size(); Cnt < E; Cnt++) {
-    auto *I = cast<Instruction>(VL[Cnt]);
+    auto *I = dyn_cast<Instruction>(VL[Cnt]);
+    if (!I)
+      continue;
+
+    // Cannot combine poison and divisions.
+    if (AnyPoison && (I->isIntDivRem() || I->isArithmeticShift() ||
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dtcxzyw wrote:

AShr is cheap and it doesn't cause immediate UB.


https://github.com/llvm/llvm-project/pull/115946