From: Richard Biener <rguenther@suse.de>
Date: Thu, 6 Mar 2025 08:08:07 +0000 (+0100)
Subject: middle-end/119119 - re-gimplification of empty CTOR assignments
X-Git-Tag: releases/gcc-12.5.0~33
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=81ebacc70c3446218a347902362cc032fc615f6c;p=thirdparty%2Fgcc.git

middle-end/119119 - re-gimplification of empty CTOR assignments

The following testcase runs into a re-gimplification issue during
inlining when processing

  MEM[(struct e *)this_2(D)].a = {};

where re-gimplification does not handle assignments in the same
way than the gimplifier but instead relies on rhs_predicate_for
and gimplifying the RHS standalone.  This fails to handle
special-casing of CTORs.  The is_gimple_mem_rhs_or_call predicate
already handles clobbers but not empty CTORs so we end up in
the fallback code trying to force the CTOR into a separate stmt
using a temporary - but as we have a non-copyable type here that ICEs.

The following generalizes empty CTORs in is_gimple_mem_rhs_or_call
since those need no additional re-gimplification.

	PR middle-end/119119
	* gimplify.cc (is_gimple_mem_rhs_or_call): All empty CTORs
	are OK when not a register type.

	* g++.dg/torture/pr11911.C: New testcase.

(cherry picked from commit 3bd61c1dfaa2d7153eb4be82f423533ea937d0f9)
---

diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index a7b5a388337..ecbe58d2b05 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -556,7 +556,7 @@ is_gimple_mem_rhs_or_call (tree t)
   else
     return (is_gimple_val (t)
 	    || is_gimple_lvalue (t)
-	    || TREE_CLOBBER_P (t)
+	    || (TREE_CODE (t) == CONSTRUCTOR && CONSTRUCTOR_NELTS (t) == 0)
 	    || TREE_CODE (t) == CALL_EXPR);
 }
 
diff --git a/gcc/testsuite/g++.dg/torture/pr11911.C b/gcc/testsuite/g++.dg/torture/pr11911.C
new file mode 100644
index 00000000000..7dc836ff9b5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr11911.C
@@ -0,0 +1,21 @@
+// { dg-do compile }
+// { dg-require-effective-target c++17 }
+
+struct b {
+  int a;
+};
+struct c {
+  b d{};
+  c() = default;
+  c(c &) = delete;
+};
+struct e {
+  c a{};
+  e() {}
+};
+inline e f() { return {}; }
+struct g {
+  e cx;
+  g() : cx{f()} {}
+};
+void h() { g i; }