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File _service:tar_scm:0005-Backport-tree-optimization-Fix-load-eliding-in-SM.patch of Package gcc
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
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