On Fri, Jul 9, 2021 at 7:34 AM 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.
>
> gcc/ChangeLog:
>
> * tree-ssa-phiopt.c (used_in_seq): New function.
> (match_simplify_replacement): Don't move the statement
> if not used in sequence.
>
> 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 | 24 ++++++++++++++++++++++-
> 2 files changed, 27 insertions(+), 2 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..a237df02153 100644
> --- a/gcc/tree-ssa-phiopt.c
> +++ b/gcc/tree-ssa-phiopt.c
> @@ -934,6 +934,26 @@ gimple_simplify_phiopt (bool early_p, tree type, gimple
> *comp_stmt,
> return NULL;
> }
>
> +/* Return true if the lhs of STMT is used in the SEQ sequence
> + of statements. */
> +static bool
> +used_in_seq (gimple *stmt, gimple_seq seq)
> +{
> + tree lhs = gimple_assign_lhs (stmt);
> + for (auto gsi = gsi_start (seq); !gsi_end_p (gsi); gsi_next_nondebug
> (&gsi))
> + {
> + use_operand_p use_p;
> + ssa_op_iter iter;
> + gimple *stmt1 = gsi_stmt (gsi);
> + FOR_EACH_SSA_USE_OPERAND (use_p, stmt1, iter, SSA_OP_USE)
> + {
> + if (USE_FROM_PTR (use_p) == lhs)
> + return true;
> + }
> + }
> + return false;
> +}
> +
> /* The function match_simplify_replacement does the main work of doing the
> replacement using match and simplify. Return true if the replacement is
> done.
> Otherwise return false.
> @@ -1020,7 +1040,9 @@ match_simplify_replacement (basic_block cond_bb,
> basic_block middle_bb,
> return false;
>
> gsi = gsi_last_bb (cond_bb);
> - if (stmt_to_move)
> + if (stmt_to_move
> + && (gimple_assign_lhs (stmt_to_move) == result
> + || used_in_seq (stmt_to_move, seq)))
Err, why not insert 'seq' before moving the stmt (you'd have to fiddle
with the iterator,
using GSI_CONTINUE_LINKING I think) and then check has_zero_uses on
the (hopefully) only
def of the stmt to move?
Richard.
> {
> if (dump_file && (dump_flags & TDF_DETAILS))
> {
> --
> 2.27.0
>
