Revert "[SLP] avoid reduction transform on patterns that the backend can load-combine"

This reverts SVN r373833, as it caused a failed assert "Non-zero loop
cost expected" on building numerous projects, see PR43582 for details
and reproduction samples.

llvm-svn: 373882

1 files changed, 3 insertions, 12 deletions

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index ad12646bdee..99428c6c5de 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -6499,19 +6499,10 @@ private:
 
     int ScalarReduxCost = 0;
     switch (ReductionData.getKind()) {
-    case RK_Arithmetic: {
-      // Note: Passing in the reduction operands allows the cost model to match
-      //       load combining patterns for this reduction.
-      auto *ReduxInst = cast<Instruction>(ReductionRoot);
-      SmallVector<const Value *, 2> OperandList;
-      for (Value *Operand : ReduxInst->operands())
-        OperandList.push_back(Operand);
-      ScalarReduxCost = TTI->getArithmeticInstrCost(ReductionData.getOpcode(),
-          ScalarTy, TargetTransformInfo::OK_AnyValue,
-          TargetTransformInfo::OK_AnyValue, TargetTransformInfo::OP_None,
-          TargetTransformInfo::OP_None, OperandList);
+    case RK_Arithmetic:
+      ScalarReduxCost =
+          TTI->getArithmeticInstrCost(ReductionData.getOpcode(), ScalarTy);
       break;
-    }
     case RK_Min:
     case RK_Max:
     case RK_UMin: