[llvm] [ValueTracking] Add support for `trunc nuw/nsw` in isKnowNonZero (PR #89643)

[Yingwei Zheng via llvm-commits]

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@@ -2632,6 +2632,13 @@ static bool isKnownNonZeroFromOperator(const Operator *I,
             Q.DL.getTypeSizeInBits(I->getType()).getFixedValue())
       return isKnownNonZero(I->getOperand(0), Q, Depth);
     break;
+  case Instruction::Trunc: {
+    auto *TI = cast<TruncInst>(I);
+    // nuw/nsw trunc preserves zero/non-zero status of input.
+    if (TI->hasNoSignedWrap() || TI->hasNoUnsignedWrap())
+      return isKnownNonZero(TI->getOperand(0), Q, Depth + 1);
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dtcxzyw wrote:

https://github.com/llvm/llvm-project/blob/d5093aac543dfd24f339f7d43aa02282f7c16fa5/llvm/lib/Analysis/ValueTracking.cpp#L3075-L3077

https://github.com/llvm/llvm-project/pull/89643