[VPlan] Add m_FirstActiveLane matcher (NFC).

Add m_FirstActiveLane, to slightly simplify pattern matching in
preparation for llvm/llvm-project#149042.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h

@@ -400,6 +400,12 @@ m_AnyOf(const Op0_t &Op0) {
   return m_VPInstruction<VPInstruction::AnyOf>(Op0);
 }
 
+template <typename Op0_t>
+inline VPInstruction_match<VPInstruction::FirstActiveLane, Op0_t>
+m_FirstActiveLane(const Op0_t &Op0) {
+  return m_VPInstruction<VPInstruction::FirstActiveLane>(Op0);
+}
+
 template <unsigned Opcode, typename Op0_t>
 inline AllRecipe_match<Opcode, Op0_t> m_Unary(const Op0_t &Op0) {
   return AllRecipe_match<Opcode, Op0_t>(Op0);

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -788,9 +788,7 @@ static VPValue *optimizeEarlyExitInductionUser(VPlan &Plan,
                                                ScalarEvolution &SE) {
   VPValue *Incoming, *Mask;
   if (!match(Op, m_VPInstruction<VPInstruction::ExtractLane>(
-                     m_VPInstruction<VPInstruction::FirstActiveLane>(
-                         m_VPValue(Mask)),
-                     m_VPValue(Incoming))))
+                     m_FirstActiveLane(m_VPValue(Mask)), m_VPValue(Incoming))))
     return nullptr;
 
   auto *WideIV = getOptimizableIVOf(Incoming, SE);

llvm/lib/Transforms/Vectorize/VPlanUnroll.cpp

@@ -352,8 +352,7 @@ void UnrollState::unrollBlock(VPBlockBase *VPB) {
     // Compute*Result which combine all parts to compute the final value.
     VPValue *Op1;
     if (match(&R, m_VPInstruction<VPInstruction::AnyOf>(m_VPValue(Op1))) ||
-        match(&R, m_VPInstruction<VPInstruction::FirstActiveLane>(
-                      m_VPValue(Op1))) ||
+        match(&R, m_FirstActiveLane(m_VPValue(Op1))) ||
         match(&R, m_VPInstruction<VPInstruction::ComputeAnyOfResult>(
                       m_VPValue(), m_VPValue(), m_VPValue(Op1))) ||
         match(&R, m_VPInstruction<VPInstruction::ComputeReductionResult>(