address comments: using arithmetic right shift

Author: zhaoqi5

llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp

@@ -2807,8 +2807,7 @@ LoongArchTargetLowering::lowerEXTRACT_VECTOR_ELT(SDValue Op,
     // The original desired i8/i16 element is now replicated in each
     // i32 lane of the splatted vector.
     SDValue NewIdx = DAG.getNode(
-        LoongArchISD::BSTRPICK, DL, GRLenVT, Idx,
-        DAG.getConstant(31, DL, GRLenVT),
+        ISD::SRA, DL, GRLenVT, Idx,
         DAG.getConstant(((VecTy == MVT::v32i8) ? 2 : 1), DL, GRLenVT));
     SDValue SplatIdx = DAG.getSplatBuildVector(MVT::v8i32, DL, NewIdx);
     SDValue SplatValue =

llvm/test/CodeGen/LoongArch/lasx/ir-instruction/extractelement.ll

@@ -77,7 +77,7 @@ define void @extract_32xi8_idx(ptr %src, ptr %dst, i32 %idx) nounwind {
 ; CHECK-LABEL: extract_32xi8_idx:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    xvld $xr0, $a0, 0
-; CHECK-NEXT:    bstrpick.d $a0, $a2, 31, 2
+; CHECK-NEXT:    srai.d $a0, $a2, 2
 ; CHECK-NEXT:    xvreplgr2vr.w $xr1, $a0
 ; CHECK-NEXT:    xvperm.w $xr0, $xr0, $xr1
 ; CHECK-NEXT:    andi $a0, $a2, 3
@@ -94,7 +94,7 @@ define void @extract_16xi16_idx(ptr %src, ptr %dst, i32 %idx) nounwind {
 ; CHECK-LABEL: extract_16xi16_idx:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    xvld $xr0, $a0, 0
-; CHECK-NEXT:    bstrpick.d $a0, $a2, 31, 1
+; CHECK-NEXT:    srai.d $a0, $a2, 1
 ; CHECK-NEXT:    xvreplgr2vr.w $xr1, $a0
 ; CHECK-NEXT:    xvperm.w $xr0, $xr0, $xr1
 ; CHECK-NEXT:    andi $a0, $a2, 1