c836983671
VPBlendRecipe does not use the first mask operand. Removing it allows VPlan-based DCE to remove unused mask computations. This also fixes #87410, where unused Not VPInstructions are considered having only their first lane demanded, but some of their operands providing a vector value due to other users. Fixes https://github.com/llvm/llvm-project/issues/87410 PR: https://github.com/llvm/llvm-project/pull/87770