[llvm] [ValueTracking] Add support for `llvm.vector.reduce.{xor,or,and}` ops. (PR #88320)

[via llvm-commits]

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@@ -1624,14 +1624,31 @@ static void computeKnownBitsFromOperator(const Operator *I,
         computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
         Known = KnownBits::ssub_sat(Known, Known2);
         break;
-        // for min/max reduce, any bit common to each element in the input vec
-        // is set in the output.
+        // for min/max/and/or reduce, any bit common to each element in the
+        // input vec is set in the output.
+      case Intrinsic::vector_reduce_and:
+      case Intrinsic::vector_reduce_or:
       case Intrinsic::vector_reduce_umax:
       case Intrinsic::vector_reduce_umin:
       case Intrinsic::vector_reduce_smax:
       case Intrinsic::vector_reduce_smin:
         computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
         break;
+      case Intrinsic::vector_reduce_xor: {
+        computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
+        // The zeros common to all vecs are zero in the output.
+        // If the number of elements is odd, then the common ones remain. If the
+        // number of elements is even, then the common ones becomes zeros.
+        auto *VecTy = cast<VectorType>(I->getOperand(0)->getType());
+        // Even, so the ones become zeros.
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goldsteinn wrote:

Guess the idea is the top comment explains what the block will do. The lower comments explain what the next few lines will do. With this minimal code though yeah it does become a bit redundant, but comments are like sex so...

https://github.com/llvm/llvm-project/pull/88320