[X86] Lower SEXTLOAD using SIGN_EXTEND_VECTOR_INREG. NCI.

The custom lowering in LowerExtendedLoad is doing the equivalent shuffle, so make use of existing lowering code to reduce duplication.

llvm-svn: 249243

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -15057,29 +15057,12 @@ static SDValue LowerExtendedLoad(SDValue Op, const X86Subtarget *Subtarget,
       return Sext;
     }
 
-    // Otherwise we'll shuffle the small elements in the high bits of the
-    // larger type and perform an arithmetic shift. If the shift is not legal
-    // it's better to scalarize.
-    assert(TLI.isOperationLegalOrCustom(ISD::SRA, RegVT) &&
-           "We can't implement a sext load without an arithmetic right shift!");
-
-    // Redistribute the loaded elements into the different locations.
-    SmallVector<int, 16> ShuffleVec(NumElems * SizeRatio, -1);
-    for (unsigned i = 0; i != NumElems; ++i)
-      ShuffleVec[i * SizeRatio + SizeRatio - 1] = i;
-
-    SDValue Shuff = DAG.getVectorShuffle(
-        WideVecVT, dl, SlicedVec, DAG.getUNDEF(WideVecVT), &ShuffleVec[0]);
-
-    Shuff = DAG.getBitcast(RegVT, Shuff);
-
-    // Build the arithmetic shift.
-    unsigned Amt = RegVT.getVectorElementType().getSizeInBits() -
-                   MemVT.getVectorElementType().getSizeInBits();
-    Shuff =
-        DAG.getNode(ISD::SRA, dl, RegVT, Shuff,
-                    DAG.getConstant(Amt, dl, RegVT));
+    // Otherwise we'll use SIGN_EXTEND_VECTOR_INREG to sign extend the lowest
+    // lanes.
+    assert(TLI.isOperationLegalOrCustom(ISD::SIGN_EXTEND_VECTOR_INREG, RegVT) &&
+           "We can't implement a sext load without SIGN_EXTEND_VECTOR_INREG!");
 
+    SDValue Shuff = DAG.getSignExtendVectorInReg(SlicedVec, dl, RegVT);
     DAG.ReplaceAllUsesOfValueWith(SDValue(Ld, 1), TF);
     return Shuff;
   }