99 lines
3.1 KiB
Diff
99 lines
3.1 KiB
Diff
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From b8b3e29e4cceae2bab6e0774b1af994dbe713d97 Mon Sep 17 00:00:00 2001
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From: zhanghaijian <z.zhanghaijian@huawei.com>
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Date: Thu, 15 Jul 2021 09:13:11 +0800
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Subject: [PATCH 10/13] [Backport]tree-optimization/94963 - avoid bogus uninit
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warning with store-motion
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Reference: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=371905d12259c180efb9b1f1b5716e969feb60f9
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Eliding the load for store-motion causes an uninitialized variable
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flowing into the loop, conditionally initialized and used. The
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uninit warning cannot relate the flag used to guard the initialization
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and use with the actual initialization so the following robustifies
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the previous approach of marking the conditional store as not to
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be warned on by instead initializing the variable on loop entry
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from an uninitialized variable we mark as not to be warned for.
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diff --git a/gcc/testsuite/gcc.dg/pr94963.c b/gcc/testsuite/gcc.dg/pr94963.c
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new file mode 100644
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index 00000000000..09c0524fb3a
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--- /dev/null
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+++ b/gcc/testsuite/gcc.dg/pr94963.c
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@@ -0,0 +1,35 @@
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+/* { dg-do compile } */
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+/* { dg-options "-O2 -Wall" } */
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+
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+typedef struct
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+{
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+ int p1;
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+ int p2;
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+ int p3;
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+} P;
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+struct S
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+{
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+ int field;
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+};
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+extern int v2;
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+extern void foo (struct S *map);
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+static struct S var;
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+const P *pv;
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+int ps;
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+void
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+f (void)
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+{
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+ if (pv != 0)
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+ for (const P *ph = pv; ph < &pv[ps]; ++ph)
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+ switch (ph->p1)
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+ {
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+ case 1:
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+ v2 = ph->p2;
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+ break;
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+ case 2:
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+ var.field = ph->p3;
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+ break;
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+ }
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+ if (var.field != 0) /* { dg-bogus "uninitialized" } */
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+ foo (&var);
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+}
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diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
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index 8c33735b1fa..d74a46ef352 100644
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--- a/gcc/tree-ssa-loop-im.c
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+++ b/gcc/tree-ssa-loop-im.c
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@@ -1994,8 +1994,6 @@ execute_sm_if_changed (edge ex, tree mem, tree tmp_var, tree flag,
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gsi = gsi_start_bb (then_bb);
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/* Insert actual store. */
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stmt = gimple_build_assign (unshare_expr (mem), tmp_var);
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- /* Make sure to not warn about maybe-uninit uses of tmp_var here. */
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- gimple_set_no_warning (stmt, true);
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gsi_insert_after (&gsi, stmt, GSI_CONTINUE_LINKING);
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edge e1 = single_succ_edge (new_bb);
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@@ -2149,13 +2147,19 @@ execute_sm (class loop *loop, vec<edge> exits, im_mem_ref *ref)
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store then. */
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if ((!always_stored && !multi_threaded_model_p)
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|| (ref->loaded && bitmap_bit_p (ref->loaded, loop->num)))
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+ load = gimple_build_assign (tmp_var, unshare_expr (ref->mem.ref));
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+ else
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{
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- load = gimple_build_assign (tmp_var, unshare_expr (ref->mem.ref));
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- lim_data = init_lim_data (load);
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- lim_data->max_loop = loop;
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- lim_data->tgt_loop = loop;
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- gsi_insert_before (&gsi, load, GSI_SAME_STMT);
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+ /* If not emitting a load mark the uninitialized state on the
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+ loop entry as not to be warned for. */
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+ tree uninit = create_tmp_reg (TREE_TYPE (tmp_var));
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+ TREE_NO_WARNING (uninit) = 1;
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+ load = gimple_build_assign (tmp_var, uninit);
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}
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+ lim_data = init_lim_data (load);
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+ lim_data->max_loop = loop;
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+ lim_data->tgt_loop = loop;
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+ gsi_insert_before (&gsi, load, GSI_SAME_STMT);
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if (multi_threaded_model_p)
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{
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--
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2.21.0.windows.1
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