[gcc r16-9339] a68: avoid coalescing of stmt_lists in a68_lower_unit_list

[Jose E. Marchesi]

https://gcc.gnu.org/g:49d5f085fbf955b542f47afc7f76c92f7ed732de

commit r16-9339-g49d5f085fbf955b542f47afc7f76c92f7ed732de
Author: Jose E. Marchesi <jemarch@gnu.org>
Date:   Sat Jun 13 18:44:27 2026 +0200

    a68: avoid coalescing of stmt_lists in a68_lower_unit_list
    
    At it happens, a68_lower_unit_list collects units as members of a
    stmt_list, lowering them and appending them.  Problem is, stmt_lists
    get coalesced when appended (or prepended) to another stmt_list.
    
    One of the units that may lower in a stmt_list are generators, and the
    coalescing manifests itself when the generators are found in
    collateral clauses.
    
    This patch puts in place a temporary workaround for this, which is to
    wrap the stmt_list into a NOP_EXPR.  This avoid the coalescing, but a
    less hackish solution will probably consist on changing the way
    unit_lists get collected instead.
    
    Signed-off-by: Jose E. Marchesi <jemarch@gnu.org>
    
    gcc/algol68/ChangeLog
    
            * a68-low-generator.cc (a68_low_generator): Wrap the resulting
            stmt_list into a nop_expr.
    
    gcc/testsuite/ChangeLog
    
            * algol68/execute/gen-in-constructor-1.a68: New test.
            * algol68/execute/gen-in-constructor-2.a68: Likewise.
    
    (cherry picked from commit 3781bb37cf83b8a6849c626236e5023b9eb9fe12)

Diff:
---
 gcc/algol68/a68-low-generator.cc                       | 3 +++
 gcc/testsuite/algol68/execute/gen-in-constructor-1.a68 | 7 +++++++
 gcc/testsuite/algol68/execute/gen-in-constructor-2.a68 | 7 +++++++
 3 files changed, 17 insertions(+)

diff --git a/gcc/algol68/a68-low-generator.cc b/gcc/algol68/a68-low-generator.cc
index e321b7d5ec28..e619b046a038 100644
--- a/gcc/algol68/a68-low-generator.cc
+++ b/gcc/algol68/a68-low-generator.cc
@@ -509,6 +509,9 @@ a68_low_generator (NODE_T *declarer,
       tree_stmt_iterator bounds_iter = tsi_start (bounds);
       tree gen = gen_mode (mode, &bounds_iter,
 			   heap ? a68_lower_malloc : a68_lower_alloca);
+      /* XXX ugly hack to avoid the resulting stmt_list to be coalesced
+	 on the current stmt_list in a68_lower_unit_list.  */
+      gen = build1 (NOP_EXPR, TREE_TYPE (gen), gen);
       return gen;
     }
 }
diff --git a/gcc/testsuite/algol68/execute/gen-in-constructor-1.a68 b/gcc/testsuite/algol68/execute/gen-in-constructor-1.a68
new file mode 100644
index 000000000000..6cf40f44b755
--- /dev/null
+++ b/gcc/testsuite/algol68/execute/gen-in-constructor-1.a68
@@ -0,0 +1,7 @@
+begin mode Foo = struct (ref[]int lala, bool sign);
+      Foo zero = (heap[3:10]int, true);
+      assert(sign'zero = true);
+      assert(UPB lala'zero = 10);
+      assert(LWB lala'zero = 3);
+      skip
+end
diff --git a/gcc/testsuite/algol68/execute/gen-in-constructor-2.a68 b/gcc/testsuite/algol68/execute/gen-in-constructor-2.a68
new file mode 100644
index 000000000000..9e67620c4d21
--- /dev/null
+++ b/gcc/testsuite/algol68/execute/gen-in-constructor-2.a68
@@ -0,0 +1,7 @@
+begin mode Foo = struct (bool sign, ref[]int lala);
+      Foo zero = (false, heap[0:-1]int);
+      assert(sign'zero = false);
+      assert(UPB lala'zero = -1);
+      assert(LWB lala'zero = 0);
+      skip
+end