On Fri, Jul 9, 2021 at 10:05 PM apinski--- via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> From: Andrew Pinski <apin...@marvell.com>
>
> Instead of waiting for DCE to remove the unused statement,
> and maybe optimize another conditional, it is better if
> we don't move the statement and have the statement
> removed.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu.
OK.
Thanks,
Richard.
> Changes from v1:
> * v2: Change the order of insertation and check to see if the lhs
> is used rather than see if the lhs was used in the sequence.
>
> gcc/ChangeLog:
>
> * tree-ssa-phiopt.c (match_simplify_replacement): Move
> insert of the sequence before the movement of the
> statement. Check if to see if the statement is used
> outside of the original phi to see if we should move it.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/tree-ssa/pr96928-1.c: Update to similar as pr96928.c.
> ---
> gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c | 5 ++++-
> gcc/tree-ssa-phiopt.c | 13 ++++++++++---
> 2 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> index 2e86620da11..9e505ac9900 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> @@ -2,7 +2,10 @@
> /* { dg-do compile } */
> /* { dg-options "-O2 -fdump-tree-phiopt2 -fdump-tree-optimized" } */
> /* { dg-final { scan-tree-dump-times " = a_\[0-9]*\\\(D\\\) >> " 5 "phiopt2"
> } } */
> -/* { dg-final { scan-tree-dump-times " = ~c_\[0-9]*\\\(D\\\);" 1 "phiopt2" }
> } */
> +/* The following check is done at optimized because a ^ (~b) is rewritten as
> ~(a^b)
> + and in the case of match.pd optimizing these ?:, the ~ is moved out
> already
> + by the time we get to phiopt2. */
> +/* { dg-final { scan-tree-dump-times "c_\[0-9]*\\\(D\\\) \\\^" 1 "optimized"
> } } */
> /* { dg-final { scan-tree-dump-times " = ~" 1 "optimized" } } */
> /* { dg-final { scan-tree-dump-times " = \[abc_0-9\\\(\\\)D]* \\\^ " 5
> "phiopt2" } } */
> /* { dg-final { scan-tree-dump-not "a < 0" "phiopt2" } } */
> diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
> index 7a98b7afdf1..c6adbbd28a0 100644
> --- a/gcc/tree-ssa-phiopt.c
> +++ b/gcc/tree-ssa-phiopt.c
> @@ -1020,7 +1020,16 @@ match_simplify_replacement (basic_block cond_bb,
> basic_block middle_bb,
> return false;
>
> gsi = gsi_last_bb (cond_bb);
> - if (stmt_to_move)
> + /* Insert the sequence generated from gimple_simplify_phiopt. */
> + if (seq)
> + gsi_insert_seq_before (&gsi, seq, GSI_CONTINUE_LINKING);
> +
> + /* If there was a statement to move and the result of the statement
> + is going to be used, move it to right before the original
> + conditional. */
> + if (stmt_to_move
> + && (gimple_assign_lhs (stmt_to_move) == result
> + || !has_single_use (gimple_assign_lhs (stmt_to_move))))
> {
> if (dump_file && (dump_flags & TDF_DETAILS))
> {
> @@ -1032,8 +1041,6 @@ match_simplify_replacement (basic_block cond_bb,
> basic_block middle_bb,
> gsi_move_before (&gsi1, &gsi);
> reset_flow_sensitive_info (gimple_assign_lhs (stmt_to_move));
> }
> - if (seq)
> - gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
>
> replace_phi_edge_with_variable (cond_bb, e1, phi, result);
>
> --
> 2.27.0
>
