[gcc r12-7517] tree-optimization/104782 - adjust PR101636 fix

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:5db1d7f143c77543ae7a6c4649af3e611061e0d9

commit r12-7517-g5db1d7f143c77543ae7a6c4649af3e611061e0d9
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Mar 7 11:11:44 2022 +0100

    tree-optimization/104782 - adjust PR101636 fix
    
    This reverts the reversion of r10-5979 amending the CTOR case
    with a comment as to why the conversion is not necessary there.
    It also adds a testcase (but not for the CTOR case).
    
    2022-03-07  Richard Biener  <rguenther@suse.de>
    
            PR tree-optimization/104782
            * tree-vect-slp.cc (vectorize_slp_instance_root_stmt):
            Re-instantiate r10-5979 fix, add comment.
    
            * gcc.dg/vect/pr104782.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/vect/pr104782.c | 18 ++++++++++++++++++
 gcc/tree-vect-slp.cc                 |  7 +++++++
 2 files changed, 25 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/vect/pr104782.c b/gcc/testsuite/gcc.dg/vect/pr104782.c
new file mode 100644
index 00000000000..7b8ca6ca25b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr104782.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-O3" } */
+/* { dg-additional-options "-march=armv8.2-a+sve -msve-vector-bits=128" { target aarch64-*-* } } */
+
+int a, b, c;
+static int d;
+short *q;
+void f() {
+  int *p = &d;
+  b = 9;
+  for (b = 9; b; b--) {
+    a = 2;
+    for (c = 2; c <= 9; c++) {
+      for (int i = 0; i < 3; i++)
+        *p |= (*q)++;
+    }
+  }
+}
diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index f9bbc872a99..4ac2b70303c 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -7382,6 +7382,10 @@ vectorize_slp_instance_root_stmt (slp_tree node, slp_instance instance)
 	  gimple *child_stmt = SLP_TREE_VEC_STMTS (node)[0];
 	  tree vect_lhs = gimple_get_lhs (child_stmt);
 	  tree root_lhs = gimple_get_lhs (instance->root_stmts[0]->stmt);
+	  if (!useless_type_conversion_p (TREE_TYPE (root_lhs),
+					  TREE_TYPE (vect_lhs)))
+	    vect_lhs = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (root_lhs),
+			       vect_lhs);
 	  rstmt = gimple_build_assign (root_lhs, vect_lhs);
 	}
       else if (SLP_TREE_NUMBER_OF_VEC_STMTS (node) > 1)
@@ -7392,6 +7396,9 @@ vectorize_slp_instance_root_stmt (slp_tree node, slp_instance instance)
 	  vec<constructor_elt, va_gc> *v;
 	  vec_alloc (v, nelts);
 
+	  /* A CTOR can handle V16HI composition from VNx8HI so we
+	     do not need to convert vector elements if the types
+	     do not match.  */
 	  FOR_EACH_VEC_ELT (SLP_TREE_VEC_STMTS (node), j, child_stmt)
 	    CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
 				    gimple_get_lhs (child_stmt));