Hi Richard,
On 14/09/16 21:31, Richard Biener wrote:
On Fri, Sep 2, 2016 at 10:09 AM, Kugan Vivekanandarajah
<kugan.vivekanandara...@linaro.org> wrote:
Hi Richard,
On 25 August 2016 at 22:24, Richard Biener <richard.guent...@gmail.com> wrote:
On Thu, Aug 11, 2016 at 1:09 AM, kugan
<kugan.vivekanandara...@linaro.org> wrote:
Hi,
On 10/08/16 20:28, Richard Biener wrote:
On Wed, Aug 10, 2016 at 10:57 AM, Jakub Jelinek <ja...@redhat.com> wrote:
On Wed, Aug 10, 2016 at 08:51:32AM +1000, kugan wrote:
I see it now. The problem is we are just looking at (-1) being in the
ops
list for passing changed to rewrite_expr_tree in the case of
multiplication
by negate. If we have combined (-1), as in the testcase, we will not
have
the (-1) and will pass changed=false to rewrite_expr_tree.
We should set changed based on what happens in try_special_add_to_ops.
Attached patch does this. Bootstrap and regression testing are ongoing.
Is
this OK for trunk if there is no regression.
I think the bug is elsewhere. In particular in
undistribute_ops_list/zero_one_operation/decrement_power.
All those look problematic in this regard, they change RHS of statements
to something that holds a different value, while keeping the LHS.
So, generally you should instead just add a new stmt next to the old one,
and adjust data structures (replace the old SSA_NAME in some ->op with
the new one). decrement_power might be a problem here, dunno if all the
builtins are const in all cases that DSE would kill the old one,
Richard, any preferences for that? reset flow sensitive info + reset
debug
stmt uses, or something different? Though, replacing the LHS with a new
anonymous SSA_NAME might be needed too, in case it is before SSA_NAME of
a
user var that doesn't yet have any debug stmts.
I'd say replacing the LHS is the way to go, with calling the appropriate
helper
on the old stmt to generate a debug stmt for it / its uses (would need
to look it
up here).
Here is an attempt to fix it. The problem arises when in
undistribute_ops_list, we linearize_expr_tree such that NEGATE_EXPR is added
(-1) MULT_EXPR (OP). Real problem starts when we handle this in
zero_one_operation. Unlike what was done earlier, we now change the stmt
(with propagate_op_to_signle use or by directly) such that the value
computed by stmt is no longer what it used to be. Because of this, what is
computed in undistribute_ops_list and rewrite_expr_tree are also changed.
undistribute_ops_list already expects this but rewrite_expr_tree will not if
we dont pass the changed as an argument.
The way I am fixing this now is, in linearize_expr_tree, I set ops_changed
to true if we change NEGATE_EXPR to (-1) MULT_EXPR (OP). Then when we call
zero_one_operation with ops_changed = true, I replace all the LHS in
zero_one_operation with the new SSA and replace all the uses. I also call
the rewrite_expr_tree with changed = false in this case.
Does this make sense? Bootstrapped and regression tested for
x86_64-linux-gnu without any new regressions.
I don't think this solves the issue. zero_one_operation associates the
chain starting at the first *def and it will change the intermediate values
of _all_ of the stmts visited until the operation to be removed is found.
Note that this is independent of whether try_special_add_to_ops did anything.
Even for the regular undistribution cases we get this wrong.
So we need to back-track in zero_one_operation, replacing each LHS
and in the end the op in the opvector of the main chain. That's basically
the same as if we'd do a regular re-assoc operation on the sub-chains.
Take their subops, simulate zero_one_operation by
appending the cancelling operation and optimizing the oplist, and then
materializing the associated ops via rewrite_expr_tree.
Here is a draft patch which records the stmt chain when in
zero_one_operation and then fixes it when OP is removed. when we
update *def, that will update the ops vector. Does this looks sane?
Yes. A few comments below
+ /* PR72835 - Record the stmt chain that has to be updated such that
+ we dont use the same LHS when the values computed are different. */
+ auto_vec<gimple *> stmts_to_fix;
use auto_vec<gimple *, 64> here so we get stack allocation only most
of the times
Done.
if (stmt_is_power_of_op (stmt, op))
{
+ make_new_ssa_for_all_defs (def, op, stmts_to_fix);
if (decrement_power (stmt) == 1)
propagate_op_to_single_use (op, stmt, def);
for the cases you end up with propagate_op_to_single_use its argument
stmt is handled superfluosly in the new SSA making, I suggest to pop it
from the stmts_to_fix vector in that case. I suggest to break; instead
of return in all cases and do the make_new_ssa_for_all_defs call at
the function end instead.
Done.
@@ -1253,14 +1305,18 @@ zero_one_operation (tree *def, enum tree_code
opcode, tree op)
if (gimple_assign_rhs1 (stmt2) == op)
{
tree cst = build_minus_one_cst (TREE_TYPE (op));
+ stmts_to_fix.safe_push (stmt2);
+ make_new_ssa_for_all_defs (def, op, stmts_to_fix);
propagate_op_to_single_use (cst, stmt2, def);
return;
this safe_push should be unnecessary for the above reason (others are
conditionally unnecessary).
Done.
Bootstrapped and regression tested on X86_64-linux-gnu with no new
regression. Is this OK?
Thanks,
Kugan
I thought about simplifying the whole thing by instead of clearing an
op from the chain pre-pend
one that does the job by means of visiting the chain from reassoc
itself but that doesn't work out
for RDIV_EXPR nor does it play well with undistribute handling
mutliple opportunities on the same
chain.
Thanks,
Richard.
Bootstrapped and regression tested on x86_64-linux-gnu with no new regressions.
Thanks,
Kugan
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr72835.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr72835.c
index e69de29..468e0f0 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr72835.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr72835.c
@@ -0,0 +1,37 @@
+/* PR tree-optimization/72835. */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+/* { dg-require-effective-target int32plus } */
+
+struct struct_1 {
+ unsigned int m1 : 6 ;
+ unsigned int m2 : 24 ;
+ unsigned int m3 : 6 ;
+};
+
+unsigned short var_32 = 0x2d10;
+
+struct struct_1 s1;
+
+void init ()
+{
+ s1.m1 = 4;
+ s1.m2 = 0x7ca4b8;
+ s1.m3 = 24;
+}
+
+void foo ()
+{
+ unsigned int c
+ = ((unsigned int) s1.m2) * (-((unsigned int) s1.m3))
+ + (var_32) * (-((unsigned int) (s1.m1)));
+ if (c != 4098873984)
+ __builtin_abort ();
+}
+
+int main ()
+{
+ init ();
+ foo ();
+ return 0;
+}
diff --git a/gcc/tree-ssa-reassoc.c b/gcc/tree-ssa-reassoc.c
index 7fd7550..24e9dd6 100644
--- a/gcc/tree-ssa-reassoc.c
+++ b/gcc/tree-ssa-reassoc.c
@@ -1148,6 +1148,52 @@ decrement_power (gimple *stmt)
}
}
+/* Replace SSA defined by STMT and replace all its uses with new
+ SSA. Also return the new SSA. */
+
+static tree
+make_new_ssa_for_def (gimple *stmt)
+{
+ gimple *use_stmt;
+ use_operand_p use;
+ imm_use_iterator iter;
+ tree new_lhs;
+ tree lhs = gimple_assign_lhs (stmt);
+
+ new_lhs = make_ssa_name (TREE_TYPE (lhs));
+ gimple_set_lhs (stmt, new_lhs);
+
+ /* Also need to update GIMPLE_DEBUGs. */
+ FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs)
+ {
+ FOR_EACH_IMM_USE_ON_STMT (use, iter)
+ SET_USE (use, new_lhs);
+ update_stmt (use_stmt);
+ }
+ return new_lhs;
+}
+
+/* Replace all SSAs defined in STMTS_TO_FIX and replace its
+ uses with new SSAs. Also do this for the stmt that defines DEF
+ if *DEF is not OP. */
+
+static void
+make_new_ssa_for_all_defs (tree *def, tree op,
+ auto_vec<gimple *, 64> &stmts_to_fix)
+{
+ unsigned i;
+ gimple *stmt;
+
+ if (*def != op
+ && TREE_CODE (*def) == SSA_NAME
+ && (stmt = SSA_NAME_DEF_STMT (*def))
+ && gimple_code (stmt) != GIMPLE_NOP)
+ *def = make_new_ssa_for_def (stmt);
+
+ FOR_EACH_VEC_ELT (stmts_to_fix, i, stmt)
+ make_new_ssa_for_def (stmt);
+}
+
/* Find the single immediate use of STMT's LHS, and replace it
with OP. Remove STMT. If STMT's LHS is the same as *DEF,
replace *DEF with OP as well. */
@@ -1186,6 +1232,9 @@ static void
zero_one_operation (tree *def, enum tree_code opcode, tree op)
{
gimple *stmt = SSA_NAME_DEF_STMT (*def);
+ /* PR72835 - Record the stmt chain that has to be updated such that
+ we dont use the same LHS when the values computed are different. */
+ auto_vec<gimple *, 64> stmts_to_fix;
do
{
@@ -1196,23 +1245,29 @@ zero_one_operation (tree *def, enum tree_code opcode,
tree op)
if (stmt_is_power_of_op (stmt, op))
{
if (decrement_power (stmt) == 1)
- propagate_op_to_single_use (op, stmt, def);
- return;
+ {
+ if (stmts_to_fix.length () > 0)
+ stmts_to_fix.pop ();
+ propagate_op_to_single_use (op, stmt, def);
+ }
+ break;
}
else if (gimple_assign_rhs_code (stmt) == NEGATE_EXPR)
{
if (gimple_assign_rhs1 (stmt) == op)
{
tree cst = build_minus_one_cst (TREE_TYPE (op));
+ if (stmts_to_fix.length () > 0)
+ stmts_to_fix.pop ();
propagate_op_to_single_use (cst, stmt, def);
- return;
+ break;
}
else if (integer_minus_onep (op)
|| real_minus_onep (op))
{
gimple_assign_set_rhs_code
(stmt, TREE_CODE (gimple_assign_rhs1 (stmt)));
- return;
+ break;
}
}
}
@@ -1228,8 +1283,10 @@ zero_one_operation (tree *def, enum tree_code opcode,
tree op)
{
if (name == op)
name = gimple_assign_rhs2 (stmt);
+ if (stmts_to_fix.length () > 0)
+ stmts_to_fix.pop ();
propagate_op_to_single_use (name, stmt, def);
- return;
+ break;
}
/* We might have a multiply of two __builtin_pow* calls, and
@@ -1245,7 +1302,9 @@ zero_one_operation (tree *def, enum tree_code opcode,
tree op)
{
if (decrement_power (stmt2) == 1)
propagate_op_to_single_use (op, stmt2, def);
- return;
+ else
+ stmts_to_fix.safe_push (stmt2);
+ break;
}
else if (is_gimple_assign (stmt2)
&& gimple_assign_rhs_code (stmt2) == NEGATE_EXPR)
@@ -1254,14 +1313,15 @@ zero_one_operation (tree *def, enum tree_code opcode,
tree op)
{
tree cst = build_minus_one_cst (TREE_TYPE (op));
propagate_op_to_single_use (cst, stmt2, def);
- return;
+ break;
}
else if (integer_minus_onep (op)
|| real_minus_onep (op))
{
+ stmts_to_fix.safe_push (stmt2);
gimple_assign_set_rhs_code
(stmt2, TREE_CODE (gimple_assign_rhs1 (stmt2)));
- return;
+ break;
}
}
}
@@ -1270,8 +1330,12 @@ zero_one_operation (tree *def, enum tree_code opcode,
tree op)
gcc_assert (name != op
&& TREE_CODE (name) == SSA_NAME);
stmt = SSA_NAME_DEF_STMT (name);
+ stmts_to_fix.safe_push (stmt);
}
while (1);
+
+ if (stmts_to_fix.length () > 0)
+ make_new_ssa_for_all_defs (def, op, stmts_to_fix);
}
/* Returns true if statement S1 dominates statement S2. Like
