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[PATCH 2/3] [asan] Factorize condition insertion code out of build_check_stmt
- From: Dodji Seketeli <dodji at redhat dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: Jakub Jelinek <jakub at redhat dot com>, Diego Novillo <dnovillo at google dot com>, Xinliang David Li <davidxl at google dot com>, Wei Mi <wmi at google dot com>
- Date: Tue, 23 Oct 2012 15:08:07 +0200
- Subject: [PATCH 2/3] [asan] Factorize condition insertion code out of build_check_stmt
- References: <87liex8hjt.fsf@redhat.com>
This patch splits a new create_cond_insert_point_before_iter function
out of build_check_stmt, to be used by a later patch.
Tested by running cc1 -fasan on the test program below with and
without the patch and by inspecting the gimple output to see that
there is no change.
void
foo ()
{
char foo[1] = {0};
foo[0] = 1;
}
gcc/
* asan.c (create_cond_insert_point_before_iter): Factorize out of ...
(build_check_stmt): ... here.
---
gcc/asan.c | 122 +++++++++++++++++++++++++++++++++++++++----------------------
1 file changed, 78 insertions(+), 44 deletions(-)
diff --git a/gcc/asan.c b/gcc/asan.c
index e201f75..aed1a60 100644
--- a/gcc/asan.c
+++ b/gcc/asan.c
@@ -397,6 +397,77 @@ asan_init_func (void)
#define PROB_VERY_UNLIKELY (REG_BR_PROB_BASE / 2000 - 1)
#define PROB_ALWAYS (REG_BR_PROB_BASE)
+/* Split the current basic block and create a condition statement
+ insertion point right before the statement pointed to by ITER.
+ Return an iterator to the point at which the caller might safely
+ insert the condition statement.
+
+ THEN_BLOCK must be set to the address of an uninitialized instance
+ of basic_block. The function will then set *THEN_BLOCK to the
+ 'then block' of the condition statement to be inserted by the
+ caller.
+
+ Similarly, the function will set *FALLTRHOUGH_BLOCK to the 'else
+ block' of the condition statement to be inserted by the caller.
+
+ Note that *FALLTHROUGH_BLOCK is a new block that contains the
+ statements starting from *ITER, and *THEN_BLOCK is a new empty
+ block.
+
+ *ITER is adjusted to still point to the same statement it was
+ *pointing to initially. */
+
+static gimple_stmt_iterator
+create_cond_insert_point_before_iter (gimple_stmt_iterator *iter,
+ bool then_more_likely_p,
+ basic_block *then_block,
+ basic_block *fallthrough_block)
+{
+ gcc_assert (then_block != NULL && fallthrough_block != NULL);
+
+ gimple_stmt_iterator gsi = *iter;
+
+ if (!gsi_end_p (gsi))
+ gsi_prev (&gsi);
+
+ basic_block cur_bb = gsi_bb (*iter);
+
+ edge e = split_block (cur_bb, gsi_stmt (gsi));
+
+ /* Get a hold on the 'condition block', the 'then block' and the
+ 'else block'. */
+ basic_block cond_bb = e->src;
+ basic_block fallthru_bb = e->dest;
+ basic_block then_bb = create_empty_bb (cond_bb);
+
+ /* Set up the newly created 'then block'. */
+ e = make_edge (cond_bb, then_bb, EDGE_TRUE_VALUE);
+ int fallthrough_probability =
+ then_more_likely_p
+ ? PROB_VERY_UNLIKELY
+ : PROB_ALWAYS - PROB_VERY_UNLIKELY;
+ e->probability = PROB_ALWAYS - fallthrough_probability;
+ make_single_succ_edge (then_bb, fallthru_bb, EDGE_FALLTHRU);
+
+ /* Set up the the fallthrough basic block. */
+ e = find_edge (cond_bb, fallthru_bb);
+ e->flags = EDGE_FALSE_VALUE;
+ e->count = cond_bb->count;
+ e->probability = fallthrough_probability;
+
+ /* Update dominance info for the newly created then_bb; note that
+ fallthru_bb's dominance info has already been updated by
+ split_bock. */
+ if (dom_info_available_p (CDI_DOMINATORS))
+ set_immediate_dominator (CDI_DOMINATORS, then_bb, cond_bb);
+
+ *then_block = then_bb;
+ *fallthrough_block = fallthru_bb;
+ *iter = gsi_start_bb (fallthru_bb);
+
+ return gsi_last_bb (cond_bb);
+}
+
/* Instrument the memory access instruction BASE. Insert new
statements before ITER.
@@ -411,8 +482,7 @@ build_check_stmt (tree base, gimple_stmt_iterator *iter,
int size_in_bytes)
{
gimple_stmt_iterator gsi;
- basic_block cond_bb, then_bb, else_bb;
- edge e;
+ basic_block then_bb, else_bb;
tree t, base_addr, shadow;
gimple g;
tree shadow_ptr_type = shadow_ptr_types[size_in_bytes == 16 ? 1 : 0];
@@ -421,51 +491,15 @@ build_check_stmt (tree base, gimple_stmt_iterator *iter,
= build_nonstandard_integer_type (TYPE_PRECISION (TREE_TYPE (base)), 1);
tree base_ssa = base;
- /* We first need to split the current basic block, and start altering
- the CFG. This allows us to insert the statements we're about to
- construct into the right basic blocks. */
-
- cond_bb = gimple_bb (gsi_stmt (*iter));
- gsi = *iter;
- gsi_prev (&gsi);
- if (!gsi_end_p (gsi))
- e = split_block (cond_bb, gsi_stmt (gsi));
- else
- e = split_block_after_labels (cond_bb);
- cond_bb = e->src;
- else_bb = e->dest;
-
- /* A recap at this point: else_bb is the basic block at whose head
- is the gimple statement for which this check expression is being
- built. cond_bb is the (possibly new, synthetic) basic block the
- end of which will contain the cache-lookup code, and a
- conditional that jumps to the cache-miss code or, much more
- likely, over to else_bb. */
-
- /* Create the bb that contains the crash block. */
- then_bb = create_empty_bb (cond_bb);
- e = make_edge (cond_bb, then_bb, EDGE_TRUE_VALUE);
- e->probability = PROB_VERY_UNLIKELY;
- make_single_succ_edge (then_bb, else_bb, EDGE_FALLTHRU);
-
- /* Mark the pseudo-fallthrough edge from cond_bb to else_bb. */
- e = find_edge (cond_bb, else_bb);
- e->flags = EDGE_FALSE_VALUE;
- e->count = cond_bb->count;
- e->probability = PROB_ALWAYS - PROB_VERY_UNLIKELY;
-
- /* Update dominance info. Note that bb_join's data was
- updated by split_block. */
- if (dom_info_available_p (CDI_DOMINATORS))
- {
- set_immediate_dominator (CDI_DOMINATORS, then_bb, cond_bb);
- set_immediate_dominator (CDI_DOMINATORS, else_bb, cond_bb);
- }
+ /* Get an iterator on the point where we can add the condition
+ statement for the instrumentation. */
+ gsi = create_cond_insert_point_before_iter (iter,
+ /*then_more_likely_p=*/false,
+ &then_bb,
+ &else_bb);
base = unshare_expr (base);
- gsi = gsi_last_bb (cond_bb);
-
/* If BASE can already be an SSA_NAME; in that case, do not create a
new SSA_NAME for it. */
if (TREE_CODE (base) != SSA_NAME)
--
1.7.11.7
--
Dodji