[llvm] [SCCP] Handle llvm.experimental.get.vector.length calls (PR #169527)

[Yingwei Zheng via llvm-commits]

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@@ -2098,6 +2098,32 @@ void SCCPInstVisitor::handleCallResult(CallBase &CB) {
       return (void)mergeInValue(ValueState[II], II,
                                 ValueLatticeElement::getRange(Result));
     }
+    if (II->getIntrinsicID() == Intrinsic::experimental_get_vector_length) {
+      unsigned BitWidth = CB.getType()->getScalarSizeInBits();
+      Value *CountArg = II->getArgOperand(0);
+      Value *VF = II->getArgOperand(1);
+      bool Scalable = cast<ConstantInt>(II->getArgOperand(2))->isOne();
+      ConstantRange Count = getValueState(CountArg)
+                                .asConstantRange(CountArg->getType(), false)
+                                .zextOrTrunc(BitWidth);
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dtcxzyw wrote:

`i32 @llvm.experimental.get.vector.length.i64(i64 2**33, i32 4, i1 false)` will be folded to zero.


https://github.com/llvm/llvm-project/pull/169527