[VPlan] Add VPBasicBlock::phis() helper (NFC).

This patch introduces a helper to obtain an iterator range for the
PHI-like recipes in a block.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D100101

lib/Transforms/Vectorize/VPlan.cpp

@@ -249,10 +249,7 @@ void VPBlockBase::deleteCFG(VPBlockBase *Entry) {
 
 VPBasicBlock::iterator VPBasicBlock::getFirstNonPhi() {
   iterator It = begin();
-  while (It != end() && (isa<VPWidenPHIRecipe>(&*It) ||
-                         isa<VPWidenIntOrFpInductionRecipe>(&*It) ||
-                         isa<VPPredInstPHIRecipe>(&*It) ||
-                         isa<VPWidenCanonicalIVRecipe>(&*It)))
+  while (It != end() && It->isPhi())
     It++;
   return It;
 }

lib/Transforms/Vectorize/VPlan.h

@@ -685,6 +685,12 @@ public:
 
   /// Returns true if the recipe may have side-effects.
   bool mayHaveSideEffects() const;
+
+  /// Returns true for PHI-like recipes.
+  bool isPhi() const {
+    return getVPDefID() == VPWidenIntOrFpInductionSC || getVPDefID() == VPWidenPHISC ||
+      getVPDefID() == VPPredInstPHISC || getVPDefID() == VPWidenCanonicalIVSC;
+  }
 };
 
 inline bool VPUser::classof(const VPDef *Def) {
@@ -1430,7 +1436,7 @@ public:
 
 /// VPBasicBlock serves as the leaf of the Hierarchical Control-Flow Graph. It
 /// holds a sequence of zero or more VPRecipe's each representing a sequence of
-/// output IR instructions.
+/// output IR instructions. All PHI-like recipes must come before any non-PHI recipes.
 class VPBasicBlock : public VPBlockBase {
 public:
   using RecipeListTy = iplist<VPRecipeBase>;
@@ -1508,6 +1514,11 @@ public:
   /// Return the position of the first non-phi node recipe in the block.
   iterator getFirstNonPhi();
 
+  /// Returns an iterator range over the PHI-like recipes in the block.
+  iterator_range<iterator> phis() {
+    return make_range(begin(), getFirstNonPhi());
+  }
+
   void dropAllReferences(VPValue *NewValue) override;
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)