[llvm] [LLVM][VPlan] Keep all VPBlend masks until VPlan transformation. (PR #104015)

[Paul Walker via llvm-commits]

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@@ -2033,12 +2033,12 @@ class VPReductionPHIRecipe : public VPHeaderPHIRecipe {
 class VPBlendRecipe : public VPSingleDefRecipe {
 public:
   /// The blend operation is a User of the incoming values and of their
-  /// respective masks, ordered [I0, I1, M1, I2, M2, ...]. Note that the first
-  /// incoming value does not have a mask associated.
+  /// respective masks, ordered [I0, M0, I1, M1, I2, M2, ...]. Note that M0 can
+  /// be ommited (implied by passing an odd number of operands) in which case
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paulwalker-arm wrote:

Fix in 6932f47cfdf4734d68759586047aee240861058e

https://github.com/llvm/llvm-project/pull/104015