On Wed, Oct 16, 2013 at 2:02 AM, Richard Biener <rguent...@suse.de> wrote:
> On Tue, 15 Oct 2013, Cong Hou wrote:
>
>> Thank you for your reminder, Jeff! I just noticed Richard's comment. I
>> have modified the patch according to that.
>>
>> The new patch is attached.
>
> (posting patches inline is easier for review, now you have to deal
> with no quoting markers ;))
>
> Comments inline.
>
> diff --git a/gcc/ChangeLog b/gcc/ChangeLog
> index 8a38316..2637309 100644
> --- a/gcc/ChangeLog
> +++ b/gcc/ChangeLog
> @@ -1,3 +1,8 @@
> +2013-10-15 Cong Hou <co...@google.com>
> +
> + * tree-vect-loop-manip.c (vect_loop_versioning): Hoist loop invariant
> + statement that contains data refs with zero-step.
> +
> 2013-10-14 David Malcolm <dmalc...@redhat.com>
>
> * dumpfile.h (gcc::dump_manager): New class, to hold state
> diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
> index 075d071..9d0f4a5 100644
> --- a/gcc/testsuite/ChangeLog
> +++ b/gcc/testsuite/ChangeLog
> @@ -1,3 +1,7 @@
> +2013-10-15 Cong Hou <co...@google.com>
> +
> + * gcc.dg/vect/pr58508.c: New test.
> +
> 2013-10-14 Tobias Burnus <bur...@net-b.de>
>
> PR fortran/58658
> diff --git a/gcc/testsuite/gcc.dg/vect/pr58508.c
> b/gcc/testsuite/gcc.dg/vect/pr58508.c
> new file mode 100644
> index 0000000..cb22b50
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr58508.c
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -ftree-vectorize -fdump-tree-vect-details" } */
> +
> +
> +/* The GCC vectorizer generates loop versioning for the following loop
> + since there may exist aliasing between A and B. The predicate checks
> + if A may alias with B across all iterations. Then for the loop in
> + the true body, we can assert that *B is a loop invariant so that
> + we can hoist the load of *B before the loop body. */
> +
> +void foo (int* a, int* b)
> +{
> + int i;
> + for (i = 0; i < 100000; ++i)
> + a[i] = *b + 1;
> +}
> +
> +
> +/* { dg-final { scan-tree-dump-times "hoist" 2 "vect" } } */
> +/* { dg-final { cleanup-tree-dump "vect" } } */
> diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
> index 574446a..f4fdec2 100644
> --- a/gcc/tree-vect-loop-manip.c
> +++ b/gcc/tree-vect-loop-manip.c
> @@ -2477,6 +2477,92 @@ vect_loop_versioning (loop_vec_info loop_vinfo,
> adjust_phi_and_debug_stmts (orig_phi, e, PHI_RESULT (new_phi));
> }
>
>
> Note that applying this kind of transform at this point invalidates
> some of the earlier analysis the vectorizer performed (namely the
> def-kind which now effectively gets vect_external_def from
> vect_internal_def). In this case it doesn't seem to cause any
> issues (we re-compute the def-kind everytime we need it (how wasteful)).
>
> + /* Extract load and store statements on pointers with zero-stride
> + accesses. */
> + if (LOOP_REQUIRES_VERSIONING_FOR_ALIAS (loop_vinfo))
> + {
> + /* In the loop body, we iterate each statement to check if it is a load
> + or store. Then we check the DR_STEP of the data reference. If
> + DR_STEP is zero, then we will hoist the load statement to the loop
> + preheader, and move the store statement to the loop exit. */
>
> We don't move the store yet. Micha has a patch pending that enables
> vectorization of zero-step stores.
>
> + for (gimple_stmt_iterator si = gsi_start_bb (loop->header);
> + !gsi_end_p (si);)
>
> While technically ok now (vectorized loops contain a single basic block)
> please use LOOP_VINFO_BBS () to get at the vector of basic-blcoks
> and iterate over them like other code does.
Have done it.
>
> + {
> + gimple stmt = gsi_stmt (si);
> + stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
> + struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
> +
> + if (dr && integer_zerop (DR_STEP (dr)))
> + {
> + if (DR_IS_READ (dr))
> + {
> + if (dump_enabled_p ())
> + {
> + dump_printf_loc
> + (MSG_NOTE, vect_location,
> + "hoist the statement to outside of the loop ");
>
> "hoisting out of the vectorized loop: "
>
> + dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
> + dump_printf (MSG_NOTE, "\n");
> + }
> +
> + gsi_remove (&si, false);
> + gsi_insert_on_edge_immediate (loop_preheader_edge (loop),
> stmt);
>
> Note that this will result in a bogus VUSE on the stmt at this point which
> will be only fixed because of implementation details of loop versioning.
> Either get the correct VUSE from the loop header virtual PHI node
> preheader edge (if there is none then the current VUSE is the correct one
> to use) or clear it.
I just cleared the VUSE since I noticed that after the vectorization
pass the correct VUSE is reassigned to the load.
>
> + }
> + /* TODO: We also consider vectorizing loops containing zero-step
> + data refs as writes. For example:
> +
> + int a[N], *s;
> + for (i = 0; i < N; i++)
> + *s += a[i];
> +
> + In this case the write to *s can be also moved after the
> + loop. */
>
> Note that you then invalidate even more vectorizer analysis - you
> basically introduce a scalar reduction (you have to add a PHI node).
> Which means that the transform has to happen elsewhere.
>
> As Jakub now tries with if-conversion this would also be a candidate
> for applying the loop versioning before even starting the rest of the
> vectorizer analysis code.
>
> That said, I'd remove the TODO at this point because it's clearly not
> possible to implement just here ;)
Yes. This comment is removed.
>
> + continue;
> + }
> + else if (!dr)
> + {
> + bool hoist = true;
> + for (size_t i = 0; i < gimple_num_ops (stmt); i++)
>
> You are checking all kinds of statements, including assignments
> of which you are also checking the LHS ... restricting to
> assignments you can start walking at i = 1.
Done.
>
> + {
> + tree op = gimple_op (stmt, i);
> + if (TREE_CODE (op) == INTEGER_CST
> + || TREE_CODE (op) == REAL_CST)
>
> There are other constants as well - just check
>
> if (is_gimple_min_invariant (op))
>
> + continue;
> + if (TREE_CODE (op) == SSA_NAME)
> + {
> + gimple def = SSA_NAME_DEF_STMT (op);
> + if (def == stmt
>
> with starting at op 1 you can drop this.
>
> + || gimple_nop_p (def)
> + || !flow_bb_inside_loop_p (loop, gimple_bb (def)))
> + continue;
> + }
>
> Note that you fail to hoist if-converted code this way because
> op1 of
>
> name_1 = a_2 < b_4 ? x_5 : y_6;
>
> is 'a_2 < b_4', a tree expression and not an SSA name (ugh). Maybe
> we don't care (it's just a missed optimization), but if you are
> restricting yourself to hoisting assignments without a data-ref
> then you can walk over SSA uses on the stmt (instead of over gimple
> ops) with
>
> FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_USE)
>
> which would automagically take care of that case.
I used FOR_EACH_SSA_TREE_OPERAND() here, and then I don't have to deal
with different constant types.
>
> Can you add a testcase which involves invariant if-conversion?
> Can you add a testcase with just an invariant store to make sure
> we don't wreck it? Can you add a testcase with an invariant store
> and load (the reduction case), too?
The if-conversion case is added. But the current vectorizer will not
vectorize loops with stores to zero-stride memory access
(vect_analyze_loop() fails in this case). Are you sure to add the
testcase with this? (I still added two tests for those two cases).
>
> + hoist = false;
> + break;
> + }
>
> For example you'll hoist all labels this way (no ops), as well as the
> loop exit GIMPLE_COND in case it's operands were loop invariant,
> breaking the CFG ... so please add && is_gimple_assign () to the
> if (!dr) check ;)
Done.
I appreciate your detailed comments! The new patch is pasted below
(since tabs cannot show here I also attached a text file with the
patch including tabs).
thanks,
Cong
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8a38316..2637309 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2013-10-15 Cong Hou <co...@google.com>
+
+ * tree-vect-loop-manip.c (vect_loop_versioning): Hoist loop invariant
+ statement that contains data refs with zero-step.
+
2013-10-14 David Malcolm <dmalc...@redhat.com>
* dumpfile.h (gcc::dump_manager): New class, to hold state
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 075d071..9d0f4a5 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-10-15 Cong Hou <co...@google.com>
+
+ * gcc.dg/vect/pr58508.c: New test.
+
2013-10-14 Tobias Burnus <bur...@net-b.de>
PR fortran/58658
diff --git a/gcc/testsuite/gcc.dg/vect/pr58508.c
b/gcc/testsuite/gcc.dg/vect/pr58508.c
new file mode 100644
index 0000000..a3f6a06
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr58508.c
@@ -0,0 +1,60 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-vectorize -fdump-tree-vect-details" } */
+
+
+/* The GCC vectorizer generates loop versioning for the following loop
+ since there may exist aliasing between A and B. The predicate checks
+ if A may alias with B across all iterations. Then for the loop in
+ the true body, we can assert that *B is a loop invariant so that
+ we can hoist the load of *B before the loop body. */
+
+void test1 (int* a, int* b)
+{
+ int i;
+ for (i = 0; i < 100000; ++i)
+ a[i] = *b + 1;
+}
+
+
+/* A test case with ifcvt transformation. */
+
+void test2 (int* a, int* b)
+{
+ int i, t;
+ for (i = 0; i < 10000; ++i)
+ {
+ if (*b > 0)
+ t = *b * 2;
+ else
+ t = *b / 2;
+ a[i] = t;
+ }
+}
+
+/* A test case in which the store in the loop can be moved outside
+ in the versioned loop with alias checks. Note this loop won't
+ be vectorized. */
+
+void test3 (int* a, int* b)
+{
+ int i;
+ for (i = 0; i < 100000; ++i)
+ *a += b[i];
+}
+
+/* A test case in which the load and store in the loop to b
+ can be moved outside in the versioned loop with alias checks.
+ Note this loop won't be vectorized. */
+
+void test4 (int* a, int* b)
+{
+ int i;
+ for (i = 0; i < 100000; ++i)
+ {
+ *b += a[i];
+ a[i] = *b;
+ }
+}
+
+/* { dg-final { scan-tree-dump-times "hoist" 6 "vect" } } */
+/* { dg-final { cleanup-tree-dump "vect" } } */
diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index 574446a..ff0403b 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -2477,6 +2477,88 @@ vect_loop_versioning (loop_vec_info loop_vinfo,
adjust_phi_and_debug_stmts (orig_phi, e, PHI_RESULT (new_phi));
}
+
+ /* Extract load statements on memrefs with zero-stride accesses. */
+
+ if (LOOP_REQUIRES_VERSIONING_FOR_ALIAS (loop_vinfo))
+ {
+ /* In the loop body, we iterate each statement to check if it is a load.
+ Then we check the DR_STEP of the data reference. If DR_STEP is zero,
+ then we will hoist the load statement to the loop preheader. */
+
+ basic_block *bbs = LOOP_VINFO_BBS (loop_vinfo);
+ int nbbs = loop->num_nodes;
+
+ for (int i = 0; i < nbbs; ++i)
+ {
+ for (gimple_stmt_iterator si = gsi_start_bb (bbs[i]);
+ !gsi_end_p (si);)
+ {
+ gimple stmt = gsi_stmt (si);
+ stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
+ struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
+
+ if (dr && integer_zerop (DR_STEP (dr)))
+ {
+ if (DR_IS_READ (dr))
+ {
+ if (dump_enabled_p ())
+ {
+ dump_printf_loc
+ (MSG_NOTE, vect_location,
+ "hoisting out of the vectorized loop: ");
+ dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
+ dump_printf (MSG_NOTE, "\n");
+ }
+
+ gimple_set_vuse (stmt, NULL);
+ gsi_remove (&si, false);
+ gsi_insert_on_edge_immediate (loop_preheader_edge (loop),
+ stmt);
+ }
+ continue;
+ }
+ else if (!dr && is_gimple_assign (stmt))
+ {
+ bool hoist = true;
+ ssa_op_iter iter;
+ tree var;
+
+ /* We hoist a statement if all SSA uses in it are defined
+ outside of the loop. */
+ FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE)
+ {
+ gimple def = SSA_NAME_DEF_STMT (var);
+ if (!gimple_nop_p (def)
+ && flow_bb_inside_loop_p (loop, gimple_bb (def)))
+ {
+ hoist = false;
+ break;
+ }
+ }
+
+ if (hoist)
+ {
+ gsi_remove (&si, false);
+ gsi_insert_on_edge_immediate (loop_preheader_edge (loop),
+ stmt);
+
+ if (dump_enabled_p ())
+ {
+ dump_printf_loc
+ (MSG_NOTE, vect_location,
+ "hoisting out of the vectorized loop: ");
+ dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
+ dump_printf (MSG_NOTE, "\n");
+ }
+ continue;
+ }
+ }
+ gsi_next (&si);
+ }
+ }
+ }
+
/* End loop-exit-fixes after versioning. */
if (cond_expr_stmt_list)
>
> + if (hoist)
> + {
> + gsi_remove (&si, false);
> + gsi_insert_on_edge_immediate (loop_preheader_edge (loop),
> stmt);
> +
> + if (dump_enabled_p ())
> + {
> + dump_printf_loc
> + (MSG_NOTE, vect_location,
> + "hoist the statement to outside of the loop ");
> + dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
> + dump_printf (MSG_NOTE, "\n");
> + }
> + continue;
> + }
> + }
> + gsi_next (&si);
> + }
> + }
> +
> /* End loop-exit-fixes after versioning. */
>
> if (cond_expr_stmt_list)
>
>>
>> thanks,
>> Cong
>>
>>
>> On Tue, Oct 15, 2013 at 12:33 PM, Jeff Law <l...@redhat.com> wrote:
>> > On 10/14/13 17:31, Cong Hou wrote:
>> >>
>> >> Any comment on this patch?
>> >
>> > Richi replied in the BZ you opened.
>> >
>> > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58508
>> >
>> > Essentially he said emit the load on the edge rather than in the block
>> > itself.
>> > jeff
>> >
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8a38316..2637309 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2013-10-15 Cong Hou <co...@google.com>
+
+ * tree-vect-loop-manip.c (vect_loop_versioning): Hoist loop invariant
+ statement that contains data refs with zero-step.
+
2013-10-14 David Malcolm <dmalc...@redhat.com>
* dumpfile.h (gcc::dump_manager): New class, to hold state
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 075d071..9d0f4a5 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-10-15 Cong Hou <co...@google.com>
+
+ * gcc.dg/vect/pr58508.c: New test.
+
2013-10-14 Tobias Burnus <bur...@net-b.de>
PR fortran/58658
diff --git a/gcc/testsuite/gcc.dg/vect/pr58508.c
b/gcc/testsuite/gcc.dg/vect/pr58508.c
new file mode 100644
index 0000000..a3f6a06
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr58508.c
@@ -0,0 +1,60 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-vectorize -fdump-tree-vect-details" } */
+
+
+/* The GCC vectorizer generates loop versioning for the following loop
+ since there may exist aliasing between A and B. The predicate checks
+ if A may alias with B across all iterations. Then for the loop in
+ the true body, we can assert that *B is a loop invariant so that
+ we can hoist the load of *B before the loop body. */
+
+void test1 (int* a, int* b)
+{
+ int i;
+ for (i = 0; i < 100000; ++i)
+ a[i] = *b + 1;
+}
+
+
+/* A test case with ifcvt transformation. */
+
+void test2 (int* a, int* b)
+{
+ int i, t;
+ for (i = 0; i < 10000; ++i)
+ {
+ if (*b > 0)
+ t = *b * 2;
+ else
+ t = *b / 2;
+ a[i] = t;
+ }
+}
+
+/* A test case in which the store in the loop can be moved outside
+ in the versioned loop with alias checks. Note this loop won't
+ be vectorized. */
+
+void test3 (int* a, int* b)
+{
+ int i;
+ for (i = 0; i < 100000; ++i)
+ *a += b[i];
+}
+
+/* A test case in which the load and store in the loop to b
+ can be moved outside in the versioned loop with alias checks.
+ Note this loop won't be vectorized. */
+
+void test4 (int* a, int* b)
+{
+ int i;
+ for (i = 0; i < 100000; ++i)
+ {
+ *b += a[i];
+ a[i] = *b;
+ }
+}
+
+/* { dg-final { scan-tree-dump-times "hoist" 6 "vect" } } */
+/* { dg-final { cleanup-tree-dump "vect" } } */
diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index 574446a..ff0403b 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -2477,6 +2477,88 @@ vect_loop_versioning (loop_vec_info loop_vinfo,
adjust_phi_and_debug_stmts (orig_phi, e, PHI_RESULT (new_phi));
}
+
+ /* Extract load statements on memrefs with zero-stride accesses. */
+
+ if (LOOP_REQUIRES_VERSIONING_FOR_ALIAS (loop_vinfo))
+ {
+ /* In the loop body, we iterate each statement to check if it is a load.
+ Then we check the DR_STEP of the data reference. If DR_STEP is zero,
+ then we will hoist the load statement to the loop preheader. */
+
+ basic_block *bbs = LOOP_VINFO_BBS (loop_vinfo);
+ int nbbs = loop->num_nodes;
+
+ for (int i = 0; i < nbbs; ++i)
+ {
+ for (gimple_stmt_iterator si = gsi_start_bb (bbs[i]);
+ !gsi_end_p (si);)
+ {
+ gimple stmt = gsi_stmt (si);
+ stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
+ struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
+
+ if (dr && integer_zerop (DR_STEP (dr)))
+ {
+ if (DR_IS_READ (dr))
+ {
+ if (dump_enabled_p ())
+ {
+ dump_printf_loc
+ (MSG_NOTE, vect_location,
+ "hoisting out of the vectorized loop: ");
+ dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
+ dump_printf (MSG_NOTE, "\n");
+ }
+
+ gimple_set_vuse (stmt, NULL);
+ gsi_remove (&si, false);
+ gsi_insert_on_edge_immediate (loop_preheader_edge (loop),
+ stmt);
+ }
+ continue;
+ }
+ else if (!dr && is_gimple_assign (stmt))
+ {
+ bool hoist = true;
+ ssa_op_iter iter;
+ tree var;
+
+ /* We hoist a statement if all SSA uses in it are defined
+ outside of the loop. */
+ FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE)
+ {
+ gimple def = SSA_NAME_DEF_STMT (var);
+ if (!gimple_nop_p (def)
+ && flow_bb_inside_loop_p (loop, gimple_bb (def)))
+ {
+ hoist = false;
+ break;
+ }
+ }
+
+ if (hoist)
+ {
+ gsi_remove (&si, false);
+ gsi_insert_on_edge_immediate (loop_preheader_edge (loop),
+ stmt);
+
+ if (dump_enabled_p ())
+ {
+ dump_printf_loc
+ (MSG_NOTE, vect_location,
+ "hoisting out of the vectorized loop: ");
+ dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
+ dump_printf (MSG_NOTE, "\n");
+ }
+ continue;
+ }
+ }
+ gsi_next (&si);
+ }
+ }
+ }
+
/* End loop-exit-fixes after versioning. */
if (cond_expr_stmt_list)
