[llvm] [RISCV][DAG][TLI] Avoid scalarizing length decreasing shuffles (PR #115532)

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<!--LLVM CODE FORMAT COMMENT: {clang-format}-->


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``````````bash
git-clang-format --diff 02668f60a9b5c0d5b8b6e60b4e897f763ad59a91 e30c3d522304ba9537b5581949d0004b3df72d4e --extensions h,cpp -- llvm/include/llvm/CodeGen/TargetLowering.h llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp llvm/lib/Target/RISCV/RISCVISelLowering.h
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View the diff from clang-format here.
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``````````diff
diff --git a/llvm/include/llvm/CodeGen/TargetLowering.h b/llvm/include/llvm/CodeGen/TargetLowering.h
index 5fe2b7949c..c143a07f27 100644
--- a/llvm/include/llvm/CodeGen/TargetLowering.h
+++ b/llvm/include/llvm/CodeGen/TargetLowering.h
@@ -548,10 +548,7 @@ public:
   // In SDAG construction, should length decreasing shuffles be expanded
   // to a sequence of extracts and inserts if they can't be recognized
   // via the two extracted operand form?
-  virtual bool
-  shouldScalarizeLengthDescreasingShuffle() const {
-    return true;
-  }
+  virtual bool shouldScalarizeLengthDescreasingShuffle() const { return true; }
 
   /// Return true if integer divide is usually cheaper than a sequence of
   /// several shifts, adds, and multiplies for this target.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index f4e011e4cd..ffe81e6229 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4185,14 +4185,14 @@ void SelectionDAGBuilder::visitShuffleVector(const User &I) {
   // source operand width, then extract the original destination
   // type.
   if (!TLI.shouldScalarizeLengthDescreasingShuffle()) {
-    EVT PaddedVT = EVT::getVectorVT(*DAG.getContext(), VT.getScalarType(),
-                                    SrcNumElts);
+    EVT PaddedVT =
+        EVT::getVectorVT(*DAG.getContext(), VT.getScalarType(), SrcNumElts);
     SmallVector<int, 8> ExtendedMask(Mask);
     ExtendedMask.resize(SrcNumElts, -1);
     SDValue Result =
-      DAG.getVectorShuffle(PaddedVT, DL, Src1, Src2, ExtendedMask);
+        DAG.getVectorShuffle(PaddedVT, DL, Src1, Src2, ExtendedMask);
     Result = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, VT, Result,
-                          DAG.getVectorIdxConstant(0, DL));
+                         DAG.getVectorIdxConstant(0, DL));
     setValue(&I, Result);
     return;
   }
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.h b/llvm/lib/Target/RISCV/RISCVISelLowering.h
index a8f385a59c..a9ccad30a2 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.h
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.h
@@ -586,8 +586,7 @@ public:
   shouldExpandBuildVectorWithShuffles(EVT VT,
                                       unsigned DefinedValues) const override;
 
-  bool
-  shouldScalarizeLengthDescreasingShuffle() const override {
+  bool shouldScalarizeLengthDescreasingShuffle() const override {
     // We always prefer to pad as a canonical form.
     return false;
   }

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https://github.com/llvm/llvm-project/pull/115532