[gcc r12-3445] middle-end/102269 - avoid auto-init of empty types

[Richard Biener]

https://gcc.gnu.org/g:1dae802b685937b1dc52e49d0641c75f3186ba14

commit r12-3445-g1dae802b685937b1dc52e49d0641c75f3186ba14
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Sep 10 10:17:24 2021 +0200

    middle-end/102269 - avoid auto-init of empty types
    
    This avoids initializing empty types for which we'll eventually
    leave a .DEFERRED_INIT call without a LHS.
    
    2021-09-10  Richard Biener  <rguenther@suse.de>
    
            PR middle-end/102269
            * gimplify.c (is_var_need_auto_init): Empty types do not need
            initialization.
    
            * gcc.dg/pr102269.c: New testcase.

Diff:
---
 gcc/gimplify.c                  | 3 ++-
 gcc/testsuite/gcc.dg/pr102269.c | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 3314f76cf3f..8820f873993 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -1826,7 +1826,8 @@ is_var_need_auto_init (tree decl)
 {
   if (auto_var_p (decl)
       && (flag_auto_var_init > AUTO_INIT_UNINITIALIZED)
-      && (!lookup_attribute ("uninitialized", DECL_ATTRIBUTES (decl))))
+      && (!lookup_attribute ("uninitialized", DECL_ATTRIBUTES (decl)))
+      && !is_empty_type (TREE_TYPE (decl)))
     return true;
   return false;
 }
diff --git a/gcc/testsuite/gcc.dg/pr102269.c b/gcc/testsuite/gcc.dg/pr102269.c
new file mode 100644
index 00000000000..9d41b8fd7c7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr102269.c
@@ -0,0 +1,4 @@
+/* { dg-do compile } */
+/* { dg-options "-ftrivial-auto-var-init=zero" } */
+
+void fn() { int a[0]; }