[AArch64] Consider negated powers of 2 when calculating throughput cost

Negated powers of 2 have similar or (exact in the case of remainder) codegen with lowering sdiv. In the case of sdiv, it just negates the result in the end anyway, so nothing dissimilar at all.

Author: AZero13

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp

@@ -4005,15 +4005,15 @@ InstructionCost AArch64TTIImpl::getArithmeticInstrCost(
       // have similar cost.
       auto VT = TLI->getValueType(DL, Ty);
       if (VT.isScalarInteger() && VT.getSizeInBits() <= 64) {
-        if (Op2Info.isPowerOf2()) {
+        if (Op2Info.isPowerOf2() || Op2Info.isNegatedPowerOf2()) {
           return ISD == ISD::SDIV ? (3 * AddCost + AsrCost)
                                   : (3 * AsrCost + AddCost);
         } else {
           return MulCost + AsrCost + 2 * AddCost;
         }
       } else if (VT.isVector()) {
         InstructionCost UsraCost = 2 * AsrCost;
-        if (Op2Info.isPowerOf2()) {
+        if (Op2Info.isPowerOf2() || Op2Info.isNegatedPowerOf2()) {
           // Division with scalable types corresponds to native 'asrd'
           // instruction when SVE is available.
           // e.g. %1 = sdiv <vscale x 4 x i32> %a, splat (i32 8)