[LV] Move conditional MaskForGaps construction to load case.

Conditionally setting MaskForGaps is only needed for loads. This avoid
re-computing MaskForGaps for stores.

Suggested as independent cleanup in D147467.

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index e686508..d5b22f9 100644 (file)
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2668,14 +2668,15 @@ void InnerLoopVectorizer::vectorizeInterleaveGroup(
   State.setDebugLocFromInst(Instr);
   Value *PoisonVec = PoisonValue::get(VecTy);
 
-  Value *MaskForGaps = nullptr;
-  if (Group->requiresScalarEpilogue() && !Cost->isScalarEpilogueAllowed()) {
-    MaskForGaps = createBitMaskForGaps(Builder, VF.getKnownMinValue(), *Group);
-    assert(MaskForGaps && "Mask for Gaps is required but it is null");
-  }
-
   // Vectorize the interleaved load group.
   if (isa<LoadInst>(Instr)) {
+    Value *MaskForGaps = nullptr;
+    if (Group->requiresScalarEpilogue() && !Cost->isScalarEpilogueAllowed()) {
+      MaskForGaps =
+          createBitMaskForGaps(Builder, VF.getKnownMinValue(), *Group);
+      assert(MaskForGaps && "Mask for Gaps is required but it is null");
+    }
+
     // For each unroll part, create a wide load for the group.
     SmallVector<Value *, 2> NewLoads;
     for (unsigned Part = 0; Part < UF; Part++) {
@@ -2743,7 +2744,8 @@ void InnerLoopVectorizer::vectorizeInterleaveGroup(
   auto *SubVT = VectorType::get(ScalarTy, VF);
 
   // Vectorize the interleaved store group.
-  MaskForGaps = createBitMaskForGaps(Builder, VF.getKnownMinValue(), *Group);
+  Value *MaskForGaps =
+      createBitMaskForGaps(Builder, VF.getKnownMinValue(), *Group);
   assert((!MaskForGaps || useMaskedInterleavedAccesses(*TTI)) &&
          "masked interleaved groups are not allowed.");
   assert((!MaskForGaps || !VF.isScalable()) &&