My optimisation to avoid recursion into BBs when checking contexts lead to a failure in a case like this: static int warn_conditional(void) { if (condition) return 0; a(); if (condition == 0) return 1; r(); return 0; } because some blocks are called with different contexts and thus need to be checked multiple times. The obvious fix would be to decrease the recursion depth at the end of the BB check function, but that, while correct, leads to extremely long sparse runtimes on somewhat complex functions. Thus, this patch also makes sparse cache which contexts it has checked a block in and avoid the re-checking in that case. Signed-off-by: Johannes Berg <johannes@sipsolutions.net>