[llvm] [ValueTracking] Infer non-zero from shr (add nuw A, B), C (PR #203039)

[Nikita Popov via llvm-commits]

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@@ -3338,6 +3337,26 @@ static bool isKnownNonZeroFromOperator(const Operator *I,
     if (Known.isNegative())
       return true;
 
+    // shr (add nuw A, B), C is non-zero if A or B has a known-one bit at
+    // position >= C, because the sum >= max(A, B).
+    const APInt *ShAmtC;
+    if (Depth + 1 < MaxAnalysisRecursionDepth &&
+        match(I->getOperand(1), m_APInt(ShAmtC)) && ShAmtC->ult(BitWidth)) {
+      Value *ShiftIn = I->getOperand(0);
+      if (auto *Add = dyn_cast<OverflowingBinaryOperator>(ShiftIn);
+          Add && Add->getOpcode() == Instruction::Add &&
+          Add->hasNoUnsignedWrap()) {
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nikic wrote:

Replace this with a `m_NUWAdd()` match?

https://github.com/llvm/llvm-project/pull/203039