fix bug in context tracking code

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>

1 files changed, 3 insertions, 1 deletions

diff --git a/linearize.h b/linearize.h
index 563bf3e..32b1c1a 100644
--- a/linearize.h
+++ b/linearize.h
@@ -219,11 +219,13 @@ enum opcode {
 
 struct basic_block_list;
 struct instruction_list;
+struct context_list_list;
 
 struct basic_block {
 	struct position pos;
 	unsigned long generation;
-	int context;
+	int context_check_recursion;
+	struct context_list_list *checked_contexts;
 	struct entrypoint *ep;
 	struct basic_block_list *parents; /* sources */
 	struct basic_block_list *children; /* destinations */