Hello.
I've spent quite some time reading sanopt pass and I eventually decided to come
up
with quite simplified optimization algorithm for ASAN_MARK internal functions.
As the
most interesting (common) cases are that an ASAN_MARK unpoison is dominated by
entry
block (where we unpoison all variables). Second interesting situation is
ASAN_MARK poison
which is not followed by a ASAN_CHECK (in post dominator tree). Both these
internal functions
can be removed.
There are numbers for linux kernel (running for couple of minutes):
20306 expand ASAN_MARK
2892 Removing ASAN_MARK poison
8124 Removing ASAN_MARK unpoison
This removes 1/3 of ASAN_MARK internal function call.
For tramp3d the situation is not so happy as it massively utilizes C++
temporaries:
34163 expand ASAN_MARK
1920 Removing ASAN_MARK poison
2051 Removing ASAN_MARK unpoison
Thoughts?
Thanks,
Martin
>From c91ad7c9fa2406145467c473dc7239479635c9a2 Mon Sep 17 00:00:00 2001
From: marxin <mli...@suse.cz>
Date: Fri, 25 Nov 2016 15:05:33 +0100
Subject: [PATCH] Add sanopt for ASAN_MARK poison and unpoison.
---
gcc/sanopt.c | 235 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 234 insertions(+), 1 deletion(-)
diff --git a/gcc/sanopt.c b/gcc/sanopt.c
index 77307d9..a110db5 100644
--- a/gcc/sanopt.c
+++ b/gcc/sanopt.c
@@ -162,7 +162,6 @@ struct sanopt_ctx
int asan_num_accesses;
};
-
/* Return true if there might be any call to free/munmap operation
on any path in between DOM (which should be imm(BB)) and BB. */
@@ -671,6 +670,237 @@ public:
}; // class pass_sanopt
+static void
+sanitize_asan_mark_unpoison (void)
+{
+ /* 1) Find all BBs that contain an ASAN_MARK poison call. */
+ auto_sbitmap with_poison (last_basic_block_for_fn (cfun) + 1);
+ bitmap_clear (with_poison);
+ basic_block bb;
+
+ FOR_EACH_BB_FN (bb, cfun)
+ {
+ if (bitmap_bit_p (with_poison, bb->index))
+ continue;
+
+ gimple_stmt_iterator gsi;
+ bool finish = false;
+ for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
+ {
+ gimple *stmt = gsi_stmt (gsi);
+ if (is_gimple_call (stmt) && gimple_call_internal_p (stmt))
+ {
+ enum internal_fn ifn = gimple_call_internal_fn (stmt);
+ switch (ifn)
+ {
+ case IFN_ASAN_MARK:
+ {
+ HOST_WIDE_INT flags = tree_to_shwi (gimple_call_arg (stmt, 0));
+ bool is_clobber = (flags & ASAN_MARK_CLOBBER) != 0;
+ if (is_clobber)
+ {
+ bitmap_set_bit (with_poison, bb->index);
+ finish = true;
+ }
+ break;
+ }
+ default:
+ break;
+ }
+ }
+
+ if (finish)
+ break;
+ }
+ }
+
+ auto_sbitmap poisoned (last_basic_block_for_fn (cfun) + 1);
+ bitmap_clear (poisoned);
+ auto_sbitmap worklist (last_basic_block_for_fn (cfun) + 1);
+ bitmap_copy (worklist, with_poison);
+
+ /* 2) Propagate the information to all reachable blocks. */
+ while (!bitmap_empty_p (worklist))
+ {
+ unsigned i = bitmap_first_set_bit (worklist);
+ bitmap_clear_bit (worklist, i);
+ basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i);
+ gcc_assert (bb);
+
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (!bitmap_bit_p (poisoned, e->dest->index))
+ {
+ bitmap_set_bit (poisoned, e->dest->index);
+ bitmap_set_bit (worklist, e->dest->index);
+ }
+ }
+
+ /* 3) Iterate all BBs not included in POISONED BBs and remove unpoison
+ ASAN_MARK preceding an ASAN_MARK poison (which can still happen). */
+ FOR_EACH_BB_FN (bb, cfun)
+ {
+ if (bitmap_bit_p (poisoned, bb->index))
+ continue;
+
+ gimple_stmt_iterator gsi;
+ bool finish = false;
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);)
+ {
+ bool next = true;
+ gimple *stmt = gsi_stmt (gsi);
+ if (is_gimple_call (stmt) && gimple_call_internal_p (stmt))
+ {
+ enum internal_fn ifn = gimple_call_internal_fn (stmt);
+ switch (ifn)
+ {
+ case IFN_ASAN_MARK:
+ {
+ HOST_WIDE_INT flags
+ = tree_to_shwi (gimple_call_arg (stmt, 0));
+ bool is_clobber = (flags & ASAN_MARK_CLOBBER) != 0;
+ if (is_clobber)
+ finish = true;
+ else
+ {
+ if (dump_file)
+ fprintf (dump_file, "Removing ASAN_MARK unpoison\n");
+ unlink_stmt_vdef (stmt);
+ gsi_remove (&gsi, true);
+ next = false;
+ }
+ break;
+ }
+ default:
+ break;
+ }
+ }
+
+ if (finish)
+ break;
+
+ if (next)
+ gsi_next (&gsi);
+ }
+ }
+}
+
+static bool
+maybe_contains_asan_check (gimple *stmt)
+{
+ if (is_gimple_call (stmt))
+ {
+ if (gimple_call_internal_p (stmt))
+ {
+ enum internal_fn ifn = gimple_call_internal_fn (stmt);
+ switch (ifn)
+ {
+ case IFN_ASAN_CHECK:
+ return true;
+ default:
+ return false;
+ }
+ }
+ else
+ return true;
+ }
+ else if (is_a<gasm *> (stmt))
+ return true;
+
+ return false;
+}
+
+static void
+sanitize_asan_mark_poison (void)
+{
+ /* 1) Find all BBs that possibly contain an ASAN_CHECK. */
+ auto_sbitmap with_check (last_basic_block_for_fn (cfun) + 1);
+ bitmap_clear (with_check);
+ basic_block bb;
+
+ FOR_EACH_BB_FN (bb, cfun)
+ {
+ if (bitmap_bit_p (with_check, bb->index))
+ continue;
+
+ gimple_stmt_iterator gsi;
+ bool finish = false;
+ for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
+ {
+ gimple *stmt = gsi_stmt (gsi);
+ if (maybe_contains_asan_check (stmt))
+ {
+ bitmap_set_bit (with_check, bb->index);
+ finish = true;
+ }
+
+ if (finish)
+ break;
+ }
+ }
+
+ auto_sbitmap can_reach_check (last_basic_block_for_fn (cfun) + 1);
+ bitmap_clear (can_reach_check);
+ auto_sbitmap worklist (last_basic_block_for_fn (cfun) + 1);
+ bitmap_copy (worklist, with_check);
+
+ /* 2) Propagate the information to all definitions blocks. */
+ while (!bitmap_empty_p (worklist))
+ {
+ unsigned i = bitmap_first_set_bit (worklist);
+ bitmap_clear_bit (worklist, i);
+ basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i);
+ gcc_assert (bb);
+
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (!bitmap_bit_p (can_reach_check, e->src->index))
+ {
+ bitmap_set_bit (can_reach_check, e->src->index);
+ bitmap_set_bit (worklist, e->src->index);
+ }
+ }
+
+ /* 3) Iterate all BBs not included in CAN_REACH_CHECK BBs and remove poison
+ ASAN_MARK not followed by a call to function having an ASAN_CHECK. */
+ FOR_EACH_BB_FN (bb, cfun)
+ {
+ if (bitmap_bit_p (can_reach_check, bb->index))
+ continue;
+
+ gimple_stmt_iterator gsi;
+ bool finish = false;
+ for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
+ {
+ bool prev = true;
+ gimple *stmt = gsi_stmt (gsi);
+ if (maybe_contains_asan_check (stmt))
+ finish = true;
+ else if (gimple_call_internal_p (stmt, IFN_ASAN_MARK))
+ {
+ HOST_WIDE_INT flags = tree_to_shwi (gimple_call_arg (stmt, 0));
+ bool is_clobber = (flags & ASAN_MARK_CLOBBER) != 0;
+ if (is_clobber)
+ {
+ if (dump_file)
+ fprintf (dump_file, "Removing ASAN_MARK poison\n");
+ unlink_stmt_vdef (stmt);
+ gsi_remove (&gsi, true);
+ prev = false;
+ }
+ }
+
+ if (finish)
+ break;
+
+ if (prev)
+ gsi_prev (&gsi);
+ }
+ }
+}
+
unsigned int
pass_sanopt::execute (function *fun)
{
@@ -698,6 +928,9 @@ pass_sanopt::execute (function *fun)
bool use_calls = ASAN_INSTRUMENTATION_WITH_CALL_THRESHOLD < INT_MAX
&& asan_num_accesses >= ASAN_INSTRUMENTATION_WITH_CALL_THRESHOLD;
+ sanitize_asan_mark_unpoison ();
+ sanitize_asan_mark_poison ();
+
bool need_commit_edge_insert = false;
FOR_EACH_BB_FN (bb, fun)
{
--
2.10.2
