[llvm] [LV, VP]VP intrinsics support for the Loop Vectorizer + adding new tail-folding mode using EVL. (PR #76172)

[via llvm-commits]

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@@ -349,6 +349,43 @@ Value *VPInstruction::generateInstruction(VPTransformState &State,
     Value *Zero = ConstantInt::get(ScalarTC->getType(), 0);
     return Builder.CreateSelect(Cmp, Sub, Zero);
   }
+  case VPInstruction::ExplicitVectorLength: {
+    // Compute EVL
+    auto GetSetVL = [=](VPTransformState &State, Value *EVL) {
+      assert(EVL->getType()->isIntegerTy() &&
+             "Requested vector length should be an integer.");
+
+      // TODO: Add support for MaxSafeDist for correct loop emission.
+      assert(State.VF.isScalable() && "Expected scalable vector factor.");
+      Value *VFArg = State.Builder.getInt32(State.VF.getKnownMinValue());
+
+      Value *GVL = State.Builder.CreateIntrinsic(
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ayalz wrote:

This intrinsic effectively calls vsetvli, whose first argument should be the Application VL, and whose return value is the Effective VL (or simply VL). Yet the first argument is called `EVL` and the return value `GVL`?

https://github.com/llvm/llvm-project/pull/76172