- Result = DAG.getNode(ISD::SHL, N0.getDebugLoc(), VT,
- Result, DAG.getConstant(ShLeftAmt, ShImmTy));
+ // If the shift amount is as large as the result size (but, presumably,
+ // no larger than the source) then the useful bits of the result are
+ // zero; we can't simply return the shortened shift, because the result
+ // of that operation is undefined.
+ if (ShLeftAmt >= VT.getSizeInBits())
+ Result = DAG.getConstant(0, VT);
+ else
+ Result = DAG.getNode(ISD::SHL, N0.getDebugLoc(), VT,
+ Result, DAG.getConstant(ShLeftAmt, ShImmTy));