Taking a value and the bitwise-or it with a non-zero constant will always result in a non-zero value. In a boolean context, this is always true.
if (x | 0x4) {} // always true, intended '&'
This patch creates a new warning group -Wtautological-bitwise-compare for this warning. It also moves in the existing tautological bitwise comparisons into this group. A few other changes were needed to the CFGBuilder so that all bool contexts would be checked. The warnings in -Wtautological-bitwise-compare will be off by default due to using the CFG.