> -----Original Message-----
> From: Richard Biener <rguent...@suse.de>
> Sent: Tuesday, May 6, 2025 9:51 AM
> To: gcc-patches@gcc.gnu.org
> Cc: Tamar Christina <tamar.christ...@arm.com>; RISC-V CI <patchworks-
> c...@rivosinc.com>
> Subject: [PATCH] tree-optimization/120089 - force all PHIs live for
> early-break vect
>
> The following makes sure to even mark unsupported PHIs live when
> doing early-break vectorization since otherwise we fail to validate
> we can vectorize those and generate wrong code based on the scalar
> PHIs which would only work with a vectorization factor of one.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> It's been a bit of a whack-a-mole, and this is an area that needs
> improvement but I wanted to have sth that can be backported and
> survive the mixed loop/SLP world.
>
> I'll wait for the CI results and then plan to push, unless you
> have any comments.
Thanks,
Makes sense to me, just small question,
>
> Thanks,
> Richard.
>
> PR tree-optimization/120089
> * tree-vect-stmts.cc (vect_stmt_relevant_p): Mark all
> PHIs live when not already so and doing early-break
> vectorization.
> (vect_mark_stmts_to_be_vectorized): Skip virtual PHIs.
> * tree-vect-slp.cc (vect_analyze_slp): Robustify handling
> of early-break forced IVs.
>
> * gcc.dg/vect/vect-early-break_134-pr120089.c: New testcase.
> ---
> .../vect/vect-early-break_134-pr120089.c | 66 +++++++++++++++++++
> gcc/tree-vect-slp.cc | 17 ++---
> gcc/tree-vect-stmts.cc | 26 ++++++--
> 3 files changed, 94 insertions(+), 15 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/vect-early-break_134-pr120089.c
>
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_134-pr120089.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_134-pr120089.c
> new file mode 100644
> index 00000000000..4d8199ca637
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_134-pr120089.c
> @@ -0,0 +1,66 @@
> +/* { dg-add-options vect_early_break } */
> +/* { dg-additional-options "-funswitch-loops" } */
> +
> +#include "tree-vect.h"
> +
> +typedef int type;
> +typedef type Vec2[2];
> +
> +struct BytesVec {
> + type d[100];
> +};
> +
> +__attribute__((noipa)) struct BytesVec
> +buildVertexBufferData(const Vec2 *origVertices, bool needsZW,
> + unsigned paddingSize, unsigned long t) {
> + const unsigned vertexCount = t;
> + struct BytesVec data = (struct BytesVec){.d = {0}};
> + type *nextVertexPtr = data.d;
> +
> + for (unsigned vertexIdx = 0u; vertexIdx < vertexCount; ++vertexIdx) {
> +
> + if (vertexIdx > t)
> + __builtin_trap();
> + __builtin_memcpy(nextVertexPtr, &origVertices[vertexIdx],
> + 2 * sizeof(type));
> + nextVertexPtr += 2;
> +
> + if (needsZW) {
> + nextVertexPtr += 2;
> + }
> +
> + nextVertexPtr += paddingSize;
> + }
> +
> + return data;
> +}
> +Vec2 origVertices[] = {
> + {0, 1}, {2, 3}, {4, 5}, {6, 7},
> + {8, 9}, {10, 11}, {12, 13}, {14, 15},
> + {16, 17}, {18, 19}, {20, 21}, {22, 23},
> + {24, 25}, {26, 27}, {27, 28}, {29, 30},
> +};
> +
> +int main()
> +{
> + check_vect ();
> + struct BytesVec vec
> + = buildVertexBufferData(origVertices, false, 0,
> + sizeof(origVertices) / sizeof(origVertices[0]));
> +
> + int errors = 0;
> + for (unsigned i = 0; i < 100; i++) {
> + if (i / 2 < sizeof(origVertices) / sizeof(origVertices[0])) {
> + int ii = i;
> + int e = origVertices[ii / 2][ii % 2];
> + if (vec.d[i] != e)
> + errors++;
> + } else {
> + if (vec.d[i] != 0)
> + errors++;
> + }
> + }
> + if (errors)
> + __builtin_abort();
> + return 0;
> +}
> diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
> index 87d9ab9355a..6d5824a97bf 100644
> --- a/gcc/tree-vect-slp.cc
> +++ b/gcc/tree-vect-slp.cc
> @@ -5044,14 +5044,17 @@ vect_analyze_slp (vec_info *vinfo, unsigned
> max_tree_size,
> vec<stmt_vec_info> roots = vNULL;
> vec<tree> remain = vNULL;
> gphi *phi = as_a<gphi *> (STMT_VINFO_STMT (stmt_info));
> - stmts.create (1);
> tree def = gimple_phi_arg_def_from_edge (phi, latch_e);
> stmt_vec_info lc_info = loop_vinfo->lookup_def (def);
> - stmts.quick_push (vect_stmt_to_vectorize (lc_info));
> - vect_build_slp_instance (vinfo, slp_inst_kind_reduc_group,
> - stmts, roots, remain,
> - max_tree_size, &limit,
> - bst_map, NULL, force_single_lane);
> + if (lc_info)
> + {
> + stmts.create (1);
> + stmts.quick_push (vect_stmt_to_vectorize (lc_info));
> + vect_build_slp_instance (vinfo, slp_inst_kind_reduc_group,
> + stmts, roots, remain,
> + max_tree_size, &limit,
> + bst_map, NULL, force_single_lane);
> + }
> /* When the latch def is from a different cycle this can only
> be a induction. Build a simple instance for this.
> ??? We should be able to start discovery from the PHI
> @@ -5061,8 +5064,6 @@ vect_analyze_slp (vec_info *vinfo, unsigned
> max_tree_size,
> tem.quick_push (stmt_info);
> if (!bst_map->get (tem))
> {
> - gcc_assert (STMT_VINFO_DEF_TYPE (stmt_info)
> - == vect_induction_def);
> stmts.create (1);
> stmts.quick_push (stmt_info);
> vect_build_slp_instance (vinfo, slp_inst_kind_reduc_group,
> diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
> index 95da855e5b3..8755fa86a5c 100644
> --- a/gcc/tree-vect-stmts.cc
> +++ b/gcc/tree-vect-stmts.cc
> @@ -419,18 +419,28 @@ vect_stmt_relevant_p (stmt_vec_info stmt_info,
> loop_vec_info loop_vinfo,
> }
> }
>
> - /* Check if it's an induction and multiple exits. In this case there will
> be
> - a usage later on after peeling which is needed for the alternate exit.
> */
> + /* Check if it's a not live PHI and multiple exits. In this case
> + there will be a usage later on after peeling which is needed for the
> + alternate exit. */
> if (LOOP_VINFO_EARLY_BREAKS (loop_vinfo)
> - && STMT_VINFO_DEF_TYPE (stmt_info) == vect_induction_def)
> + && is_a <gphi *> (stmt)
> + && ((! VECTORIZABLE_CYCLE_DEF (STMT_VINFO_DEF_TYPE (stmt_info))
> + && ! *live_p)
> + || STMT_VINFO_DEF_TYPE (stmt_info) == vect_induction_def))
> {
> if (dump_enabled_p ())
> - dump_printf_loc (MSG_NOTE, vect_location,
> - "vec_stmt_relevant_p: induction forced for "
> - "early break.\n");
> + {
> + if (is_a <gphi *> (stmt))
> + dump_printf_loc (MSG_NOTE, vect_location,
> + "vec_stmt_relevant_p: PHI forced live for "
> + "early break.\n");
Isn't this always true since the condition above requires everything to always
be a phi?
Should it have been STMT_VINFO_DEF_TYPE (stmt_info) != vect_induction_def ?
Thanks,
Tamar
> + else
> + dump_printf_loc (MSG_NOTE, vect_location,
> + "vec_stmt_relevant_p: induction forced for "
> + "early break.\n");
> + }
> LOOP_VINFO_EARLY_BREAKS_LIVE_IVS (loop_vinfo).safe_push (stmt_info);
> *live_p = true;
> -
> }
>
> if (*live_p && *relevant == vect_unused_in_scope
> @@ -714,6 +724,8 @@ vect_mark_stmts_to_be_vectorized (loop_vec_info
> loop_vinfo, bool *fatal)
> bb = bbs[i];
> for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si))
> {
> + if (virtual_operand_p (gimple_phi_result (gsi_stmt (si))))
> + continue;
> stmt_vec_info phi_info = loop_vinfo->lookup_stmt (gsi_stmt (si));
> if (dump_enabled_p ())
> dump_printf_loc (MSG_NOTE, vect_location, "init: phi relevant? %G",
> --
> 2.43.0
