[gcc r12-5689] vect: Tighten check for SLP memory groups [PR103517]

[Richard Sandiford]

https://gcc.gnu.org/g:1e625a44f6f3001cea31e0f7c563943ecba92b68

commit r12-5689-g1e625a44f6f3001cea31e0f7c563943ecba92b68
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Wed Dec 1 14:36:24 2021 +0000

    vect: Tighten check for SLP memory groups [PR103517]
    
    When checking for compatible stmts, vect_build_slp_tree_1 did:
    
                   && !(STMT_VINFO_GROUPED_ACCESS (stmt_info)
                        && (first_stmt_code == ARRAY_REF
                            || first_stmt_code == BIT_FIELD_REF
                            || first_stmt_code == INDIRECT_REF
                            || first_stmt_code == COMPONENT_REF
                            || first_stmt_code == MEM_REF)))
    
    That is, it allowed any rhs_code as long as the first_stmt_code
    looked valid.  This had the effect of allowing IFN_MASK_LOAD
    to be paired with an earlier non-call code (but didn't allow
    the reverse).
    
    This patch makes the check symmetrical.
    
    gcc/
            PR tree-optimization/103517
            * tree-vect-slp.c (vect_build_slp_tree_1): When allowing two
            different component references, check the codes of both them,
            rather than just the first.
    
    gcc/testsuite/
            PR tree-optimization/103517
            * gcc.dg/vect/pr103517.c: New test.

Diff:
---
 gcc/testsuite/gcc.dg/vect/pr103517.c | 13 +++++++++++++
 gcc/tree-vect-slp.c                  |  7 ++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/vect/pr103517.c b/gcc/testsuite/gcc.dg/vect/pr103517.c
new file mode 100644
index 00000000000..de87fc48f84
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr103517.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-march=skylake-avx512" { target x86_64-*-* i?86-*-* } } */
+
+int a;
+short b, c;
+extern short d[];
+void e() {
+  for (short f = 1; f < (short)a; f += 2)
+    if (d[f + 1]) {
+      b = d[f];
+      c = d[f + 1];
+    }
+}
diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 7bff5118bd0..bc22ffeed82 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -1121,7 +1121,12 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap,
 			|| first_stmt_code == BIT_FIELD_REF
 			|| first_stmt_code == INDIRECT_REF
 			|| first_stmt_code == COMPONENT_REF
-			|| first_stmt_code == MEM_REF)))
+			|| first_stmt_code == MEM_REF)
+		    && (rhs_code == ARRAY_REF
+			|| rhs_code == BIT_FIELD_REF
+			|| rhs_code == INDIRECT_REF
+			|| rhs_code == COMPONENT_REF
+			|| rhs_code == MEM_REF)))
 	      || first_stmt_load_p != load_p
 	      || first_stmt_phi_p != phi_p)
 	    {