* [PATCH] Maintain LC SSA when doing SVE vectorization
@ 2022-07-04 13:01 Richard Biener
2022-07-05 10:41 ` Richard Sandiford
0 siblings, 1 reply; 2+ messages in thread
From: Richard Biener @ 2022-07-04 13:01 UTC (permalink / raw)
To: gcc-patches; +Cc: richard.sandiford
The final loop IV use after the loop has that not in LC SSA
(and inserts not simplified _2 = _3 - 0 stmts). In particular
since it splits the exit edge when there's a virtual PHI in the
destination it breaks virtual LC SSA form (but likely also
non-virtual).
The following properly inserts LC PHIs instead.
Bootstrap & regtest pending on x86_64-unknown-linux-gnu.
OK if that succeeds?
Thanks,
Richard.
2022-07-04 Richard Biener <rguenther@suse.de>
* tree-vect-loop-manip.cc (vect_set_loop_condition_normal):
Maintain LC SSA.
---
gcc/tree-vect-loop-manip.cc | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 895957472c9..eba71c50428 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -920,9 +920,22 @@ vect_set_loop_condition_normal (class loop *loop, tree niters, tree step,
if (final_iv)
{
- gassign *assign = gimple_build_assign (final_iv, MINUS_EXPR,
- indx_after_incr, init);
- gsi_insert_on_edge_immediate (single_exit (loop), assign);
+ gassign *assign;
+ edge exit = single_exit (loop);
+ gcc_assert (single_pred_p (exit->dest));
+ tree phi_dest
+ = integer_zerop (init) ? final_iv : copy_ssa_name (indx_after_incr);
+ /* Make sure to maintain LC SSA form here and elide the subtraction
+ if the value is zero. */
+ gphi *phi = create_phi_node (phi_dest, exit->dest);
+ add_phi_arg (phi, indx_after_incr, exit, UNKNOWN_LOCATION);
+ if (!integer_zerop (init))
+ {
+ assign = gimple_build_assign (final_iv, MINUS_EXPR,
+ phi_dest, init);
+ gimple_stmt_iterator gsi = gsi_after_labels (exit->dest);
+ gsi_insert_before (&gsi, assign, GSI_SAME_STMT);
+ }
}
return cond_stmt;
--
2.35.3
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] Maintain LC SSA when doing SVE vectorization
2022-07-04 13:01 [PATCH] Maintain LC SSA when doing SVE vectorization Richard Biener
@ 2022-07-05 10:41 ` Richard Sandiford
0 siblings, 0 replies; 2+ messages in thread
From: Richard Sandiford @ 2022-07-05 10:41 UTC (permalink / raw)
To: Richard Biener; +Cc: gcc-patches
Richard Biener <rguenther@suse.de> writes:
> The final loop IV use after the loop has that not in LC SSA
> (and inserts not simplified _2 = _3 - 0 stmts). In particular
> since it splits the exit edge when there's a virtual PHI in the
> destination it breaks virtual LC SSA form (but likely also
> non-virtual).
>
> The following properly inserts LC PHIs instead.
>
> Bootstrap & regtest pending on x86_64-unknown-linux-gnu.
>
> OK if that succeeds?
LGTM, thanks.
Richard
>
> Thanks,
> Richard.
>
> 2022-07-04 Richard Biener <rguenther@suse.de>
>
> * tree-vect-loop-manip.cc (vect_set_loop_condition_normal):
> Maintain LC SSA.
> ---
> gcc/tree-vect-loop-manip.cc | 19 ++++++++++++++++---
> 1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
> index 895957472c9..eba71c50428 100644
> --- a/gcc/tree-vect-loop-manip.cc
> +++ b/gcc/tree-vect-loop-manip.cc
> @@ -920,9 +920,22 @@ vect_set_loop_condition_normal (class loop *loop, tree niters, tree step,
>
> if (final_iv)
> {
> - gassign *assign = gimple_build_assign (final_iv, MINUS_EXPR,
> - indx_after_incr, init);
> - gsi_insert_on_edge_immediate (single_exit (loop), assign);
> + gassign *assign;
> + edge exit = single_exit (loop);
> + gcc_assert (single_pred_p (exit->dest));
> + tree phi_dest
> + = integer_zerop (init) ? final_iv : copy_ssa_name (indx_after_incr);
> + /* Make sure to maintain LC SSA form here and elide the subtraction
> + if the value is zero. */
> + gphi *phi = create_phi_node (phi_dest, exit->dest);
> + add_phi_arg (phi, indx_after_incr, exit, UNKNOWN_LOCATION);
> + if (!integer_zerop (init))
> + {
> + assign = gimple_build_assign (final_iv, MINUS_EXPR,
> + phi_dest, init);
> + gimple_stmt_iterator gsi = gsi_after_labels (exit->dest);
> + gsi_insert_before (&gsi, assign, GSI_SAME_STMT);
> + }
> }
>
> return cond_stmt;
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