> -----Original Message-----
> From: Richard Biener <rguent...@suse.de>
> Sent: Wednesday, August 27, 2025 2:56 PM
> To: gcc-patches@gcc.gnu.org
> Cc: RISC-V CI <patchworks...@rivosinc.com>; Tamar Christina
> <tamar.christ...@arm.com>
> Subject: [PATCH] Pass reduction var to vectorize_fold_left_reduction directly
>
> Instead of going via the PHI node def, use the scalar reduction
> input from the reduction stmt.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> Sorry for the re-post, this is now re-based on pristine trunk,
> hopefully making git am happy.
AArch64 and Arm are clean, I did notice an ICE on x86_64 though:
spawn -ignore SIGHUP /opt/buildAgent/temp/buildTmp/gcc/xgcc
-B/opt/buildAgent/temp/buildTmp/gcc/
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/testsuite/gcc.dg/vect/vect-cond-reduc-in-order-2-signed-zero.c
-m64 -fdiagnostics-plain-output -msse2 -ftree-vectorize
-fno-tree-loop-distribute-patterns -fno-vect-cost-model -fno-common -O2
-fdump-tree-vect-details -std=gnu99 -fno-fast-math -lm -o
./vect-cond-reduc-in-order-2-signed-zero.exe
during GIMPLE pass: vect
dump file: ./vect-cond-reduc-in-order-2-signed-zero.c.185t.vect
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/testsuite/gcc.dg/vect/vect-cond-reduc-in-order-2-signed-zero.c:
In function 'reduc_plus_double':
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/testsuite/gcc.dg/vect/vect-cond-reduc-in-order-2-signed-zero.c:13:1:
internal compiler error: in compute_live_loop_exits, at
tree-ssa-loop-manip.cc:262
0x2e864c7 internal_error(char const*, ...)
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/diagnostic-global-context.cc:534
0xf08d9c fancy_abort(char const*, int, char const*)
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/diagnostics/context.cc:1687
0x99b97d compute_live_loop_exits
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/tree-ssa-loop-manip.cc:262
0x99b97d add_exit_phis_var
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/tree-ssa-loop-manip.cc:344
0x99b97d add_exit_phis
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/tree-ssa-loop-manip.cc:404
0x19092bf rewrite_into_loop_closed_ssa_1
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/tree-ssa-loop-manip.cc:618
0x19092bf rewrite_into_loop_closed_ssa(bitmap_head*, unsigned int)
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/tree-ssa-loop-manip.cc:640
0x1ad7855 execute
/opt/buildAgent/work/505bfdd4dad8af3d/gcc/tree-vectorizer.cc:1399
The compiler was configured with:
+ /opt/buildAgent/work/505bfdd4dad8af3d/configure
--enable-checking=yes,rtl,extra --with-arch=native --enable-multilib
--with-multilib-list=m32,m64
Cheers,
Tamar
>
> * tree-vect-loop.cc (vectorize_fold_left_reduction): Get
> reduc_var as argument.
> (vect_transform_reduction): Adjust.
> ---
> gcc/tree-vect-loop.cc | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index f22613e5a3a..f48a18a593d 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -6501,7 +6501,7 @@ vectorize_fold_left_reduction (loop_vec_info
> loop_vinfo,
> stmt_vec_info stmt_info,
> gimple_stmt_iterator *gsi,
> slp_tree slp_node,
> - gimple *reduc_def_stmt,
> + tree reduc_var,
> code_helper code, internal_fn reduc_fn,
> int num_ops, tree vectype_in,
> int reduc_index, vec_loop_masks *masks,
> @@ -6546,7 +6546,6 @@ vectorize_fold_left_reduction (loop_vec_info
> loop_vinfo,
> gimple *sdef = vect_orig_stmt (scalar_dest_def_info)->stmt;
> tree scalar_dest = gimple_get_lhs (sdef);
> tree scalar_type = TREE_TYPE (scalar_dest);
> - tree reduc_var = gimple_phi_result (reduc_def_stmt);
>
> int vec_num = vec_oprnds0.length ();
> tree vec_elem_type = TREE_TYPE (vectype_out);
> @@ -8016,8 +8015,6 @@ vect_transform_reduction (loop_vec_info loop_vinfo,
> The last use is the reduction variable. In case of nested cycle this
> assumption is not true: we use reduc_index to record the index of the
> reduction variable. */
> - stmt_vec_info phi_info = STMT_VINFO_REDUC_DEF (vect_orig_stmt
> (stmt_info));
> - gphi *reduc_def_phi = as_a <gphi *> (phi_info->stmt);
> int reduc_index = STMT_VINFO_REDUC_IDX (stmt_info);
> tree vectype_in = SLP_TREE_VECTYPE (SLP_TREE_CHILDREN (slp_node)[0]);
>
> @@ -8059,8 +8056,9 @@ vect_transform_reduction (loop_vec_info loop_vinfo,
> {
> internal_fn reduc_fn = STMT_VINFO_REDUC_FN (reduc_info);
> gcc_assert (code.is_tree_code () || cond_fn_p);
> + tree reduc_var = op.ops[reduc_index];
> return vectorize_fold_left_reduction
> - (loop_vinfo, stmt_info, gsi, slp_node, reduc_def_phi,
> + (loop_vinfo, stmt_info, gsi, slp_node, reduc_var,
> code, reduc_fn, op.num_ops, vectype_in,
> reduc_index, masks, lens);
> }
> --
> 2.43.0
