1 files changed, 66 insertions, 0 deletions
diff --git a/0005-Backport-tree-optimization-Fix-load-eliding-in-SM.patch b/0005-Backport-tree-optimization-Fix-load-eliding-in-SM.patch
new file mode 100644
index 0000000..0ab01ea
--- /dev/null
+++ b/0005-Backport-tree-optimization-Fix-load-eliding-in-SM.patch
@@ -0,0 +1,66 @@
+From dc238e97a75835231939e77e8568ccd9bc5187d5 Mon Sep 17 00:00:00 2001
+From: zhanghaijian <z.zhanghaijian@huawei.com>
+Date: Mon, 12 Jul 2021 10:46:16 +0800
+Subject: [PATCH 05/13] [Backport]tree-optimization: Fix load eliding in SM
+
+Reference: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=0424a5ece5307cc22bbc0fe97edf4707d7a798ed
+
+This fixes the case of not using the multithreaded model when
+only conditionally storing to the destination.  We cannot elide
+the load in this case.
+
+diff --git a/gcc/testsuite/gcc.dg/torture/pr94949.c b/gcc/testsuite/gcc.dg/torture/pr94949.c
+new file mode 100755
+index 00000000000..6182d77b3cd
+--- /dev/null
++++ b/gcc/testsuite/gcc.dg/torture/pr94949.c
+@@ -0,0 +1,17 @@
++/* { dg-do run } */
++/* { dg-additional-options "-fallow-store-data-races" } */
++
++static int x = 1;
++static volatile int y = -1;
++int
++main()
++{
++  for (int i = 0; i < 128; ++i)
++    {
++      if (i == y)
++	x = i;
++    }
++  if (x != 1)
++    __builtin_abort ();
++  return 0;
++}
+diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
+index b3fd1647fbd..8c33735b1fa 100644
+--- a/gcc/tree-ssa-loop-im.c
++++ b/gcc/tree-ssa-loop-im.c
+@@ -2128,9 +2128,9 @@ execute_sm (class loop *loop, vec<edge> exits, im_mem_ref *ref)
+   fmt_data.orig_loop = loop;
+   for_each_index (&ref->mem.ref, force_move_till, &fmt_data);
+ 
++  bool always_stored = ref_always_accessed_p (loop, ref, true);
+   if (bb_in_transaction (loop_preheader_edge (loop)->src)
+-      || (! flag_store_data_races
+-	  && ! ref_always_accessed_p (loop, ref, true)))
++      || (! flag_store_data_races && ! always_stored))
+     multi_threaded_model_p = true;
+ 
+   if (multi_threaded_model_p)
+@@ -2145,8 +2145,10 @@ execute_sm (class loop *loop, vec<edge> exits, im_mem_ref *ref)
+ 
+   /* Avoid doing a load if there was no load of the ref in the loop.
+      Esp. when the ref is not always stored we cannot optimize it
+-     away later.  */
+-  if (ref->loaded && bitmap_bit_p (ref->loaded, loop->num))
++     away later.  But when it is not always stored we must use a conditional
++     store then.  */
++  if ((!always_stored && !multi_threaded_model_p)
++      || (ref->loaded && bitmap_bit_p (ref->loaded, loop->num)))
+     {
+       load = gimple_build_assign (tmp_var, unshare_expr (ref->mem.ref));
+       lim_data = init_lim_data (load);
+-- 
+2.21.0.windows.1
+