[llvm] [VP][EVL] Support select instruction with EVL-vectorization (PR #109614)

[Alexey Bataev via llvm-commits]

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@@ -1082,6 +1100,36 @@ void VPWidenSelectRecipe::execute(VPTransformState &State) {
   }
 }
 
+void VPWidenSelectEVLRecipe::execute(VPTransformState &State) {
+  State.setDebugLocFrom(getDebugLoc());
+  assert(State.UF == 1 && "Expected only UF == 1 when vectorizing with "
+                          "explicit vector length.");
+
+  Value *EVLArg = State.get(getEVL(), 0, /*NeedsScalar=*/true);
+  IRBuilderBase &BuilderIR = State.Builder;
+  VectorBuilder Builder(BuilderIR);
+  Builder.setEVL(EVLArg);
+  // The condition can be loop invariant but still defined inside the
+  // loop. This means that we can't just use the original 'cond' value.
+  // We have to take the 'vectorized' value and pick the first lane.
+  // Instcombine will make this a no-op.
+  auto *InvarCond =
+      isInvariantCond() ? State.get(getCond(), VPIteration(0, 0)) : nullptr;
+
+  Value *Cond = InvarCond ? InvarCond : State.get(getCond(), 0);
+  if (!isa<VectorType>(Cond->getType())) {
+    Cond = BuilderIR.CreateVectorSplat(State.VF, Cond, "splat.cond");
+  }
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alexey-bataev wrote:

Drop braces here

https://github.com/llvm/llvm-project/pull/109614