[PATCH v2] vect: Merge loop mask and cond_op mask in fold-left, reduction [PR115382].

[Robin Dapp]

> Actually, as Richard mentioned in the PR, it would probably be better
> to use prepare_vec_mask instead.  It should work in this context too
> and would avoid redundant double masking.

Attached is v2 that uses prepare_vec_mask.

Regtested on riscv64 and armv8.8-a+sve via qemu.
Bootstrap and regtest running on x86 and aarch64.

Regards
 Robin


Currently we discard the cond-op mask when the loop is fully masked
which causes wrong code in
gcc.dg/vect/vect-cond-reduc-in-order-2-signed-zero.c
when compiled with
-O3 -march=cascadelake --param vect-partial-vector-usage=2.

This patch ANDs both masks.

gcc/ChangeLog:

        PR tree-optimization/115382

        * tree-vect-loop.cc (vectorize_fold_left_reduction): Merge loop
        mask and cond-op mask.
---
 gcc/tree-vect-loop.cc  | 10 +++++++++-
 gcc/tree-vect-stmts.cc |  2 +-
 gcc/tree-vectorizer.h  |  2 ++
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 028692614bb..c9b037b8daf 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -7215,7 +7215,15 @@ vectorize_fold_left_reduction (loop_vec_info loop_vinfo,
       tree len = NULL_TREE;
       tree bias = NULL_TREE;
       if (LOOP_VINFO_FULLY_MASKED_P (loop_vinfo))
-       mask = vect_get_loop_mask (loop_vinfo, gsi, masks, vec_num, vectype_in, 
i);
+       {
+         tree loop_mask = vect_get_loop_mask (loop_vinfo, gsi, masks,
+                                              vec_num, vectype_in, i);
+         if (is_cond_op)
+           mask = prepare_vec_mask (loop_vinfo, TREE_TYPE (loop_mask),
+                                    loop_mask, vec_opmask[i], gsi);
+         else
+           mask = loop_mask;
+       }
       else if (is_cond_op)
        mask = vec_opmask[i];
       if (LOOP_VINFO_FULLY_WITH_LENGTH_P (loop_vinfo))
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index 5098b7fab6a..124a3462753 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -1643,7 +1643,7 @@ check_load_store_for_partial_vectors (loop_vec_info 
loop_vinfo, tree vectype,
    MASK_TYPE is the type of both masks.  If new statements are needed,
    insert them before GSI.  */
 
-static tree
+tree
 prepare_vec_mask (loop_vec_info loop_vinfo, tree mask_type, tree loop_mask,
                  tree vec_mask, gimple_stmt_iterator *gsi)
 {
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index 97ec9c341e7..1f87c6c8ca2 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -2508,6 +2508,8 @@ extern void vect_free_slp_tree (slp_tree);
 extern bool compatible_calls_p (gcall *, gcall *);
 extern int vect_slp_child_index_for_operand (const gimple *, int op, bool);
 
+extern tree prepare_vec_mask (loop_vec_info, tree, tree, tree, 
gimple_stmt_iterator *);
+
 /* In tree-vect-patterns.cc.  */
 extern void
 vect_mark_pattern_stmts (vec_info *, stmt_vec_info, gimple *, tree);
-- 
2.45.1