[LV] Fix PR33613 - retain order of insertelement per part

r306381 caused PR33613, by reversing the order in which insertelements were
generated per unroll part. This patch fixes PR33613 by retraining this order,
placing each set of insertelements per part immediately after the last scalar
being packed for this part. Includes a test case derived from PR33613.

Reference: https://bugs.llvm.org/show_bug.cgi?id=33613
Differential Revision: https://reviews.llvm.org/D34760

llvm-svn: 306575

1 files changed, 7 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index a442df052d9..013ad1a1cb4 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2716,13 +2716,13 @@ Value *InnerLoopVectorizer::getOrCreateVectorValue(Value *V, unsigned Part) {
       return ScalarValue;
     }
 
-    // Get the last scalar instruction we generated for V. If the value is
-    // known to be uniform after vectorization, this corresponds to lane zero
-    // of the last unroll iteration. Otherwise, the last instruction is the one
-    // we created for the last vector lane of the last unroll iteration.
+    // Get the last scalar instruction we generated for V and Part. If the value
+    // is known to be uniform after vectorization, this corresponds to lane zero
+    // of the Part unroll iteration. Otherwise, the last instruction is the one
+    // we created for the last vector lane of the Part unroll iteration.
     unsigned LastLane = Cost->isUniformAfterVectorization(I, VF) ? 0 : VF - 1;
     auto *LastInst =
-        cast<Instruction>(getOrCreateScalarValue(V, UF - 1, LastLane));
+        cast<Instruction>(VectorLoopValueMap.getScalarValue(V, Part, LastLane));
 
     // Set the insert point after the last scalarized instruction. This ensures
     // the insertelement sequence will directly follow the scalar definitions.
@@ -4047,7 +4047,8 @@ void InnerLoopVectorizer::fixFirstOrderRecurrence(PHINode *Phi) {
   auto *VecPhi = Builder.CreatePHI(VectorInit->getType(), 2, "vector.recur");
   VecPhi->addIncoming(VectorInit, LoopVectorPreHeader);
 
-  // Get the vectorized previous value.
+  // Get the vectorized previous value of the last part UF - 1. It appears last
+  // among all unrolled iterations, due to the order of their construction.
   Value *PreviousLastPart = getOrCreateVectorValue(Previous, UF - 1);
 
   // Set the insertion point after the previous value if it is an instruction.