[SDAG] Check context node for free truncates in DemandedBits (#171266)

Allow ShrinkDemandedOp to use Node-specific info

Author: natanelh-mobileye

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -630,7 +630,7 @@ bool TargetLowering::ShrinkDemandedOp(SDValue Op, unsigned BitWidth,
   for (unsigned SmallVTBits = llvm::bit_ceil(DemandedSize);
        SmallVTBits < BitWidth; SmallVTBits = NextPowerOf2(SmallVTBits)) {
     EVT SmallVT = EVT::getIntegerVT(*DAG.getContext(), SmallVTBits);
-    if (isTruncateFree(VT, SmallVT) && isZExtFree(SmallVT, VT)) {
+    if (isTruncateFree(Op, SmallVT) && isZExtFree(SmallVT, VT)) {
       // We found a type with free casts.
 
       // If the operation has the 'disjoint' flag, then the