139 lines
4.8 KiB
Diff
139 lines
4.8 KiB
Diff
From bdb0f40cea4aa1a92ead381b645363ae0571c065 Mon Sep 17 00:00:00 2001
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From: zhanghaijian <z.zhanghaijian@huawei.com>
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Date: Mon, 12 Jul 2021 10:36:15 +0800
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Subject: [PATCH 04/13] [Backport]tree-optimization: Avoid issueing loads in SM
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when possible
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Reference:https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=f9e1ea10e657af9fb02fafecf1a600740fd34409
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Currently store-motion emits a load of the value in the loop
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preheader even when the original loop does not contain any read
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of the reference. This avoids doing this. In the conditional
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store-motion case we need to mark the sunk stores with no-warning
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since the control dependence is too tricky to figure out for
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the uninit warning.
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diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr39612.c b/gcc/testsuite/gcc.dg/tree-ssa/pr39612.c
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new file mode 100755
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index 00000000000..884f905148f
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--- /dev/null
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+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr39612.c
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@@ -0,0 +1,21 @@
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+/* { dg-do compile } */
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+/* { dg-options "-O2 -fdump-tree-lim2-details -Wuninitialized" } */
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+
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+void foo(int *);
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+void f2(int dst[3], int R)
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+{
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+ int i, inter[2];
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+
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+ for (i = 1; i < R; i++) {
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+ if (i & 8)
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+ {
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+ inter[0] = 1;
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+ inter[1] = 1;
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+ }
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+ }
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+
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+ foo(inter);
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+}
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+
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+/* { dg-final { scan-tree-dump-times "Executing store motion" 2 "lim2" } } */
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+/* { dg-final { scan-tree-dump-not " = inter\\\[\[0-1\]\\\];" "lim2" } } */
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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 abd5f702b91..b3fd1647fbd 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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@@ -127,6 +127,8 @@ public:
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bitmap stored; /* The set of loops in that this memory location
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is stored to. */
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+ bitmap loaded; /* The set of loops in that this memory location
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+ is loaded from. */
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vec<mem_ref_loc> accesses_in_loop;
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/* The locations of the accesses. Vector
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indexed by the loop number. */
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@@ -1395,6 +1397,7 @@ mem_ref_alloc (ao_ref *mem, unsigned hash, unsigned id)
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ref->ref_decomposed = false;
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ref->hash = hash;
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ref->stored = NULL;
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+ ref->loaded = NULL;
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bitmap_initialize (&ref->indep_loop, &lim_bitmap_obstack);
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bitmap_initialize (&ref->dep_loop, &lim_bitmap_obstack);
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ref->accesses_in_loop.create (1);
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@@ -1435,6 +1438,27 @@ mark_ref_stored (im_mem_ref *ref, class loop *loop)
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loop = loop_outer (loop);
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}
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+/* Set the LOOP bit in REF loaded bitmap and allocate that if
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+ necessary. Return whether a bit was changed. */
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+
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+static bool
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+set_ref_loaded_in_loop (im_mem_ref *ref, class loop *loop)
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+{
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+ if (!ref->loaded)
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+ ref->loaded = BITMAP_ALLOC (&lim_bitmap_obstack);
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+ return bitmap_set_bit (ref->loaded, loop->num);
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+}
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+
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+/* Marks reference REF as loaded in LOOP. */
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+
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+static void
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+mark_ref_loaded (im_mem_ref *ref, class loop *loop)
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+{
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+ while (loop != current_loops->tree_root
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+ && set_ref_loaded_in_loop (ref, loop))
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+ loop = loop_outer (loop);
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+}
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+
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/* Gathers memory references in statement STMT in LOOP, storing the
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information about them in the memory_accesses structure. Marks
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the vops accessed through unrecognized statements there as
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@@ -1571,6 +1595,8 @@ gather_mem_refs_stmt (class loop *loop, gimple *stmt)
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bitmap_set_bit (&memory_accesses.refs_stored_in_loop[loop->num], ref->id);
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mark_ref_stored (ref, loop);
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}
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+ else
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+ mark_ref_loaded (ref, loop);
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init_lim_data (stmt)->ref = ref->id;
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return;
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}
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@@ -1968,6 +1994,8 @@ 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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@@ -2115,14 +2143,17 @@ execute_sm (class loop *loop, vec<edge> exits, im_mem_ref *ref)
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by move_computations after all dependencies. */
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gsi = gsi_for_stmt (first_mem_ref_loc (loop, ref)->stmt);
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- /* FIXME/TODO: For the multi-threaded variant, we could avoid this
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- load altogether, since the store is predicated by a flag. We
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- could, do the load only if it was originally in the loop. */
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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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+ /* Avoid doing a load if there was no load of the ref in the loop.
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+ Esp. when the ref is not always stored we cannot optimize it
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+ away later. */
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+ if (ref->loaded && bitmap_bit_p (ref->loaded, loop->num))
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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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+ }
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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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