On Sat, Jun 7, 2025 at 12:31 AM Andrew Pinski <quic_apin...@quicinc.com> wrote:
>
> So the current code iterates through the uses of the vdef of the store to see
> if there
> is an use of the vdef inside the bb. Except in this case we know the only
> usage will
> be a phi node, so change the loop into calling single_imm_use and then
> checking if the
> usage statement was the PHI node.
>
> Bootstrapped and tested on x86_64-linux-gnu.
>
> Also did a quick test by adding a return false after the checks of
> single_trailing_store_in_bb
> in cond_if_else_store_replacement to make sure this code still does the
> correct thing.
OK.
> gcc/ChangeLog:
>
> * tree-ssa-phiopt.cc (single_trailing_store_in_bb): Add vphi argument.
> Check for single use of the vdef of the store instead of a loop
> and check vdef's single use statement is the same as vphi.
> (cond_if_else_store_replacement): Update call to
> single_trailing_store_in_bb.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> gcc/tree-ssa-phiopt.cc | 22 ++++++++++++----------
> 1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
> index 2e4f9dad327..b9c753abc3a 100644
> --- a/gcc/tree-ssa-phiopt.cc
> +++ b/gcc/tree-ssa-phiopt.cc
> @@ -3708,10 +3708,11 @@ cond_if_else_store_replacement_1 (basic_block
> then_bb, basic_block else_bb,
> }
>
> /* Return the single store in BB with VDEF or NULL if there are
> - other stores in the BB or loads following the store. */
> + other stores in the BB or loads following the store. VPHI is
> + where the only use of the vdef should be. */
>
> static gimple *
> -single_trailing_store_in_bb (basic_block bb, tree vdef)
> +single_trailing_store_in_bb (basic_block bb, tree vdef, gphi *vphi)
> {
> if (SSA_NAME_IS_DEFAULT_DEF (vdef))
> return NULL;
> @@ -3726,13 +3727,14 @@ single_trailing_store_in_bb (basic_block bb, tree
> vdef)
> && gimple_code (SSA_NAME_DEF_STMT (gimple_vuse (store))) != GIMPLE_PHI)
> return NULL;
>
> - /* Verify there is no load or store after the store. */
> + /* Verify there is no load or store after the store, the vdef of the store
> + should only be used by the vphi joining the 2 bbs. */
> use_operand_p use_p;
> - imm_use_iterator imm_iter;
> - FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_vdef (store))
> - if (USE_STMT (use_p) != store
> - && gimple_bb (USE_STMT (use_p)) == bb)
> - return NULL;
> + gimple *use_stmt;
> + if (!single_imm_use (gimple_vdef (store), &use_p, &use_stmt))
> + return NULL;
> + if (use_stmt != vphi)
> + return NULL;
>
> return store;
> }
> @@ -3785,10 +3787,10 @@ cond_if_else_store_replacement (basic_block then_bb,
> basic_block else_bb,
> return false;
> tree then_vdef = PHI_ARG_DEF_FROM_EDGE (vphi, single_succ_edge (then_bb));
> tree else_vdef = PHI_ARG_DEF_FROM_EDGE (vphi, single_succ_edge (else_bb));
> - gimple *then_assign = single_trailing_store_in_bb (then_bb, then_vdef);
> + gimple *then_assign = single_trailing_store_in_bb (then_bb, then_vdef,
> vphi);
> if (then_assign)
> {
> - gimple *else_assign = single_trailing_store_in_bb (else_bb, else_vdef);
> + gimple *else_assign = single_trailing_store_in_bb (else_bb, else_vdef,
> vphi);
> if (else_assign)
> return cond_if_else_store_replacement_1 (then_bb, else_bb, join_bb,
> then_assign, else_assign,
> vphi);
> --
> 2.43.0
>
