From: Lili Cui <lili....@intel.com>
Hi Maintainer
This patch is to fix TSVC242 regression related to loop-carried ops.
Bootstrapped and regtested. Ok for trunk?
Regards
Lili.
Avoid adding loop-carried ops to long chains, otherwise the whole chain will
have dependencies across the loop iteration. Just keep loop-carried ops in a
separate chain.
E.g.
x_1 = phi(x_0, x_2)
y_1 = phi(y_0, y_2)
a + b + c + d + e + x1 + y1
SSA1 = a + b;
SSA2 = c + d;
SSA3 = SSA1 + e;
SSA4 = SSA3 + SSA2;
SSA5 = x1 + y1;
SSA6 = SSA4 + SSA5;
With the patch applied, these test cases improved by 32%~100%.
S242:
for (int i = 1; i < LEN_1D; ++i) {
a[i] = a[i - 1] + s1 + s2 + b[i] + c[i] + d[i];}
Case 1:
for (int i = 1; i < LEN_1D; ++i) {
a[i] = a[i - 1] + s1 + s2 + b[i] + c[i] + d[i] + e[i];}
Case 2:
for (int i = 1; i < LEN_1D; ++i) {
a[i] = a[i - 1] + b[i - 1] + s1 + s2 + b[i] + c[i] + d[i] + e[i];}
The value is the execution time
A: original version
B: with FMA patch g:e5405f065bace0685cb3b8878d1dfc7a6e7ef409(base on A)
C: with current patch(base on B)
A B C B/A C/A
s242 2.859 5.152 2.859 1.802028681 1
case 1 5.489 5.488 3.511 0.999818 0.64
case 2 7.216 7.499 4.885 1.039218 0.68
gcc/ChangeLog:
PR tree-optimization/110148
* tree-ssa-reassoc.cc (rewrite_expr_tree_parallel): Handle loop-carried
ops in this function.
---
gcc/tree-ssa-reassoc.cc | 236 ++++++++++++++++++++++++++++------------
1 file changed, 167 insertions(+), 69 deletions(-)
diff --git a/gcc/tree-ssa-reassoc.cc b/gcc/tree-ssa-reassoc.cc
index 96c88ec003e..f5da385e0b2 100644
--- a/gcc/tree-ssa-reassoc.cc
+++ b/gcc/tree-ssa-reassoc.cc
@@ -5471,37 +5471,62 @@ get_reassociation_width (int ops_num, enum tree_code
opc,
return width;
}
+#define SPECIAL_BIASED_END_STMT 0 /* It is the end stmt of all ops. */
+#define BIASED_END_STMT 1 /* It is the end stmt of normal or biased ops. */
+#define NORMAL_END_STMT 2 /* It is the end stmt of normal ops. */
+
/* Rewrite statements with dependency chain with regard the chance to generate
FMA.
For the chain with FMA: Try to keep fma opportunity as much as possible.
For the chain without FMA: Putting the computation in rank order and trying
to allow operations to be executed in parallel.
E.g.
- e + f + g + a * b + c * d;
+ e + f + a * b + c * d;
- ssa1 = e + f;
- ssa2 = g + a * b;
- ssa3 = ssa1 + c * d;
- ssa4 = ssa2 + ssa3;
+ ssa1 = e + a * b;
+ ssa2 = f + c * d;
+ ssa3 = ssa1 + ssa2;
This reassociation approach preserves the chance of fma generation as much
- as possible. */
+ as possible.
+
+ Another thing is to avoid adding loop-carried ops to long chains, otherwise
+ the whole chain will have dependencies across the loop iteration. Just keep
+ loop-carried ops in a separate chain.
+ E.g.
+ x_1 = phi(x_0, x_2)
+ y_1 = phi(y_0, y_2)
+
+ a + b + c + d + e + x1 + y1
+
+ SSA1 = a + b;
+ SSA2 = c + d;
+ SSA3 = SSA1 + e;
+ SSA4 = SSA3 + SSA2;
+ SSA5 = x1 + y1;
+ SSA6 = SSA4 + SSA5;
+ */
static void
rewrite_expr_tree_parallel (gassign *stmt, int width, bool has_fma,
- const vec<operand_entry *> &ops)
+ const vec<operand_entry *> &ops)
{
enum tree_code opcode = gimple_assign_rhs_code (stmt);
int op_num = ops.length ();
+ int op_normal_num = op_num;
gcc_assert (op_num > 0);
int stmt_num = op_num - 1;
gimple **stmts = XALLOCAVEC (gimple *, stmt_num);
- int op_index = op_num - 1;
- int width_count = width;
int i = 0, j = 0;
tree tmp_op[2], op1;
operand_entry *oe;
gimple *stmt1 = NULL;
tree last_rhs1 = gimple_assign_rhs1 (stmt);
+ int last_rhs1_stmt_index = 0, last_rhs2_stmt_index = 0;
+ int width_active = 0, width_count = 0;
+ bool has_biased = false, ops_changed = false;
+ auto_vec<operand_entry *> ops_normal;
+ auto_vec<operand_entry *> ops_biased;
+ vec<operand_entry *> *ops1;
/* We start expression rewriting from the top statements.
So, in this loop we create a full list of statements
@@ -5510,83 +5535,155 @@ rewrite_expr_tree_parallel (gassign *stmt, int width,
bool has_fma,
for (i = stmt_num - 2; i >= 0; i--)
stmts[i] = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (stmts[i+1]));
- /* Width should not be larger than op_num / 2, since we can not create
+ /* Avoid adding loop-carried ops to long chains, first filter out the
+ loop-carried. But we need to make sure that the length of the remainder
+ is not less than 4, which is the smallest ops length we can break the
+ dependency. */
+ FOR_EACH_VEC_ELT (ops, i, oe)
+ {
+ if (TREE_CODE (oe->op) == SSA_NAME
+ && bitmap_bit_p (biased_names, SSA_NAME_VERSION (oe->op))
+ && op_normal_num > 4)
+ {
+ ops_biased.safe_push (oe);
+ has_biased = true;
+ op_normal_num --;
+ }
+ else
+ ops_normal.safe_push (oe);
+ }
+
+ /* Width should not be larger than ops length / 2, since we can not create
more parallel dependency chains that exceeds such value. */
- width = width <= op_num / 2 ? width : op_num / 2;
+ int width_normal = op_normal_num / 2;
+ int width_biased = (op_num - op_normal_num) / 2;
+ width_normal = width <= width_normal ? width : width_normal;
+ width_biased = width <= width_biased ? width : width_biased;
+
+ ops1 = &ops_normal;
+ width_count = width_active = width_normal;
/* Build parallel dependency chain according to width. */
- for (i = 0; i < width; i++)
+ for (i = 0; i < stmt_num; i++)
{
- /* If the chain has FAM, we do not swap two operands. */
- if (op_index > 1 && !has_fma)
- swap_ops_for_binary_stmt (ops, op_index - 2);
-
- for (j = 0; j < 2; j++)
+ if (dump_file && (dump_flags & TDF_DETAILS))
{
- gcc_assert (op_index >= 0);
- oe = ops[op_index--];
- tmp_op[j] = oe->op;
- /* If the stmt that defines operand has to be inserted, insert it
- before the use. */
- stmt1 = oe->stmt_to_insert;
- if (stmt1)
- insert_stmt_before_use (stmts[i], stmt1);
- stmt1 = NULL;
+ fprintf (dump_file, "Transforming ");
+ print_gimple_stmt (dump_file, stmts[i], 0);
}
- stmts[i] = build_and_add_sum (TREE_TYPE (last_rhs1),
- tmp_op[1],
- tmp_op[0],
- opcode);
- gimple_set_visited (stmts[i], true);
- if (dump_file && (dump_flags & TDF_DETAILS))
+ /* When the work of normal ops is over, but the loop is not over,
+ continue to do biased ops. */
+ if (width_count == 0 && ops1 == &ops_normal)
{
- fprintf (dump_file, " into ");
- print_gimple_stmt (dump_file, stmts[i], 0);
+ ops1 = &ops_biased;
+ width_count = width_active = width_biased;
+ ops_changed = true;
}
- }
- for (i = width; i < stmt_num; i++)
- {
- /* We keep original statement only for the last one. All others are
- recreated. */
- if ( op_index < 0)
+ /* Swap the operands if no FMA in the chain. */
+ if (ops1->length () > 2 && !has_fma)
+ swap_ops_for_binary_stmt (*ops1, ops1->length () - 3);
+
+ if (i < width_active
+ || (ops_changed && i <= (last_rhs1_stmt_index + width_active)))
{
- if (width_count == 2)
+ for (j = 0; j < 2; j++)
{
-
- /* We keep original statement only for the last one. All
- others are recreated. */
- gimple_assign_set_rhs1 (stmts[i], gimple_assign_lhs (stmts[i-1]));
- gimple_assign_set_rhs2 (stmts[i], gimple_assign_lhs (stmts[i-2]));
- update_stmt (stmts[i]);
+ oe = ops1->pop ();
+ tmp_op[j] = oe->op;
+ /* If the stmt that defines operand has to be inserted, insert it
+ before the use. */
+ stmt1 = oe->stmt_to_insert;
+ if (stmt1)
+ insert_stmt_before_use (stmts[i], stmt1);
+ stmt1 = NULL;
}
- else
- {
+ stmts[i] = build_and_add_sum (TREE_TYPE (last_rhs1),
+ tmp_op[1],
+ tmp_op[0],
+ opcode);
+ gimple_set_visited (stmts[i], true);
- stmts[i] =
- build_and_add_sum (TREE_TYPE (last_rhs1),
- gimple_assign_lhs (stmts[i-width_count]),
- gimple_assign_lhs (stmts[i-width_count+1]),
- opcode);
- gimple_set_visited (stmts[i], true);
- width_count--;
- }
}
else
{
- /* Attach the rest of the ops to the parallel dependency chain. */
- oe = ops[op_index--];
- op1 = oe->op;
- stmt1 = oe->stmt_to_insert;
- if (stmt1)
- insert_stmt_before_use (stmts[i], stmt1);
- stmt1 = NULL;
- stmts[i] = build_and_add_sum (TREE_TYPE (last_rhs1),
- gimple_assign_lhs (stmts[i-width]),
- op1,
- opcode);
- gimple_set_visited (stmts[i], true);
+ /* We keep original statement only for the last one. All others are
+ recreated. */
+ if (!ops1->length ())
+ {
+ /* For biased length equal to 2. */
+ if (width_count == BIASED_END_STMT && !last_rhs2_stmt_index)
+ last_rhs2_stmt_index = i - 1;
+
+ /* When width_count == 2 and there is no biased, just finish. */
+ if (width_count == NORMAL_END_STMT && !has_biased)
+ {
+ last_rhs1_stmt_index = i - 1;
+ last_rhs2_stmt_index = i - 2;
+ }
+ if (last_rhs1_stmt_index && (last_rhs2_stmt_index || !has_biased))
+ {
+ /* We keep original statement only for the last one. All
+ others are recreated. */
+ gimple_assign_set_rhs1 (stmts[i], gimple_assign_lhs
(stmts[last_rhs1_stmt_index]));
+ gimple_assign_set_rhs2 (stmts[i], gimple_assign_lhs
(stmts[last_rhs2_stmt_index]));
+ update_stmt (stmts[i]);
+ }
+ else
+ {
+ stmts[i] =
+ build_and_add_sum (TREE_TYPE (last_rhs1),
+ gimple_assign_lhs (stmts[i-width_count]),
+ gimple_assign_lhs
(stmts[i-width_count+1]),
+ opcode);
+ gimple_set_visited (stmts[i], true);
+ width_count--;
+
+ /* It is the end of normal or biased ops.
+ last_rhs1_stmt_index used to record the last stmt index
+ for normal ops. last_rhs2_stmt_index used to record the
+ last stmt index for biased ops. */
+ if (width_count == BIASED_END_STMT)
+ {
+ gcc_assert (has_biased);
+ if (ops_biased.length ())
+ last_rhs1_stmt_index = i;
+ else
+ last_rhs2_stmt_index = i;
+ width_count--;
+ }
+ }
+ }
+ else
+ {
+ /* Attach the rest of the ops to the parallel dependency chain.
*/
+ oe = ops1->pop ();
+ op1 = oe->op;
+ stmt1 = oe->stmt_to_insert;
+ if (stmt1)
+ insert_stmt_before_use (stmts[i], stmt1);
+ stmt1 = NULL;
+
+ /* For only one biased ops. */
+ if (width_count == SPECIAL_BIASED_END_STMT)
+ {
+ /* We keep original statement only for the last one. All
+ others are recreated. */
+ gcc_assert (has_biased);
+ gimple_assign_set_rhs1 (stmts[i], gimple_assign_lhs
(stmts[last_rhs1_stmt_index]));
+ gimple_assign_set_rhs2 (stmts[i], op1);
+ update_stmt (stmts[i]);
+ }
+ else
+ {
+ stmts[i] = build_and_add_sum (TREE_TYPE (last_rhs1),
+ gimple_assign_lhs
(stmts[i-width_active]),
+ op1,
+ opcode);
+ gimple_set_visited (stmts[i], true);
+ }
+ }
}
if (dump_file && (dump_flags & TDF_DETAILS))
@@ -5595,6 +5692,7 @@ rewrite_expr_tree_parallel (gassign *stmt, int width,
bool has_fma,
print_gimple_stmt (dump_file, stmts[i], 0);
}
}
+
remove_visited_stmt_chain (last_rhs1);
}
--
2.25.1
