In kill_dead_stores(), instructions must be scanned backward
in order to check if the store is dead and can be removed.
However, if the corresponding pseudo has a single user,
this user is a store and the it correspond to a local symbol,
then it's not needed to scan, the store can be directly be removed.
This is somehow important for some semi-pathological case where
some BB contains a lot of dead stores because the current way is
annoyingly O(n^2).
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
flow.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/flow.c b/flow.c
index cc6158723..2c685cee6 100644
--- a/flow.c
+++ b/flow.c
@@ -770,11 +770,38 @@ void simplify_symbol_usage(struct entrypoint *ep)
} END_FOR_EACH_PTR(pseudo);
}
+static struct pseudo_user *first_user(pseudo_t p)
+{
+ struct pseudo_user *pu;
+ FOR_EACH_PTR(p->users, pu) {
+ if (!pu)
+ continue;
+ return pu;
+ } END_FOR_EACH_PTR(pu);
+ return NULL;
+}
+
void kill_dead_stores(struct entrypoint *ep, pseudo_t addr, int local)
{
unsigned long generation;
struct basic_block *bb;
+ switch (pseudo_user_list_size(addr->users)) {
+ case 0:
+ return;
+ case 1:
+ if (local) {
+ struct pseudo_user *pu = first_user(addr);
+ struct instruction *insn = pu->insn;
+ if (insn->opcode == OP_STORE) {
+ kill_instruction_force(insn);
+ return;
+ }
+ }
+ default:
+ break;
+ }
+
generation = ++bb_generation;
FOR_EACH_PTR(ep->bbs, bb) {
if (bb->children)
--
2.16.2
--
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