[llvm] Generate `kmov` for masking integers (PR #120593)

[Phoebe Wang via llvm-commits]

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@@ -4975,12 +4975,70 @@ bool X86DAGToDAGISel::tryVPTESTM(SDNode *Root, SDValue Setcc,
     return tryFoldBroadcast(Root, P, L, Base, Scale, Index, Disp, Segment);
   };
 
+  auto canUseKMOV = [&]() {
+    if (Src0.getOpcode() != X86ISD::VBROADCAST)
+      return false;
+
+    if (Src1.getOpcode() != ISD::LOAD ||
+        Src1.getOperand(1).getOpcode() != X86ISD::Wrapper ||
+        Src1.getOperand(1).getOperand(0).getOpcode() != ISD::TargetConstantPool)
+      return false;
+
+    const auto *ConstPool =
+        dyn_cast<ConstantPoolSDNode>(Src1.getOperand(1).getOperand(0));
+    if (!ConstPool)
+      return false;
+
+    const auto *ConstVec = ConstPool->getConstVal();
+    const auto *ConstVecType = dyn_cast<FixedVectorType>(ConstVec->getType());
+    if (!ConstVecType)
+      return false;
+
+    for (unsigned i = 0, e = ConstVecType->getNumElements(), k = 1; i != e;
+         ++i, k *= 2) {
+      const auto *Element = ConstVec->getAggregateElement(i);
+      if (llvm::isa<llvm::UndefValue>(Element)) {
+        for (unsigned j = i + 1; j != e; ++j) {
+          if (!llvm::isa<llvm::UndefValue>(ConstVec->getAggregateElement(j)))
+            return false;
+        }
+        return i != 0;
+      }
+
+      if (Element->getUniqueInteger() != k) {
----------------
phoebewang wrote:

`k` is meaningless, use a meaningful name or simply `1 << i` here.

https://github.com/llvm/llvm-project/pull/120593