[PATCH,fortran] Fix Bug 93554 - [13/14/15/16 Regression] ICE in expand_oacc_for ...

From c1c11ab69115f14e2914fb8c135f5e4f9061a4fa Mon Sep 17 00:00:00 2001
From: Christopher Albert <[email protected]>
Date: Fri, 3 Apr 2026 18:37:54 +0200
Subject: [PATCH] fortran: Fix ICE in expand_oacc_for with private derived type
 [PR93554]

Using a derived type with an allocatable component in a private clause
on an OpenACC loop caused an ICE in expand_oacc_for because the
finalization code for the allocatable component inserted additional
basic blocks between the loop's continuation/entry blocks and the exit
block, violating the strict CFG assertions.

The assertions checked that BRANCH_EDGE(entry_bb)->dest == exit_bb and
FALLTHRU_EDGE(cont_bb)->dest == exit_bb, but with finalization blocks
these edges can point to intermediate blocks rather than directly to
the exit.  Relax the assertions to only verify the expected edge count
(two successors) without requiring specific destinations.

	PR fortran/93554

gcc/ChangeLog:

	* omp-expand.cc (expand_oacc_for): Relax entry_bb and cont_bb
	assertions to allow intermediate blocks from finalization code.
	Remove exit_bb predecessor count assertion.

gcc/testsuite/ChangeLog:

	* gfortran.dg/goacc/pr93554.f90: New test.

Signed-off-by: Christopher Albert <[email protected]>
---
 gcc/omp-expand.cc                           | 13 +++++--------
 gcc/testsuite/gfortran.dg/goacc/pr93554.f90 | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/goacc/pr93554.f90

diff --git a/gcc/omp-expand.cc b/gcc/omp-expand.cc
index 2b4467cab82..f7db4542b7d 100644
--- a/gcc/omp-expand.cc
+++ b/gcc/omp-expand.cc
@@ -7718,28 +7718,25 @@ expand_oacc_for (struct omp_region *region, struct omp_for_data *fd)
   basic_block bottom_bb = NULL;
 
   /* entry_bb has two successors; the branch edge is to the exit
-     block, fallthrough edge to body.  */
-  gcc_assert (EDGE_COUNT (entry_bb->succs) == 2
-	      && BRANCH_EDGE (entry_bb)->dest == exit_bb);
+     block (or to finalization blocks preceding it), fallthrough edge
+     to body.  */
+  gcc_assert (EDGE_COUNT (entry_bb->succs) == 2);
 
   /* If cont_bb non-NULL, it has 2 successors.  The branch successor is
      body_bb, or to a block whose only successor is the body_bb.  Its
      fallthrough successor is the final block (same as the branch
-     successor of the entry_bb).  */
+     successor of the entry_bb), possibly via finalization blocks.  */
   if (cont_bb)
     {
       basic_block body_bb = FALLTHRU_EDGE (entry_bb)->dest;
       basic_block bed = BRANCH_EDGE (cont_bb)->dest;
 
-      gcc_assert (FALLTHRU_EDGE (cont_bb)->dest == exit_bb);
+      gcc_assert (EDGE_COUNT (cont_bb->succs) == 2);
       gcc_assert (bed == body_bb || single_succ_edge (bed)->dest == body_bb);
     }
   else
     gcc_assert (!gimple_in_ssa_p (cfun));
 
-  /* The exit block only has entry_bb and cont_bb as predecessors.  */
-  gcc_assert (EDGE_COUNT (exit_bb->preds) == 1 + (cont_bb != NULL));
-
   tree chunk_no;
   tree chunk_max = NULL_TREE;
   tree bound, offset;
diff --git a/gcc/testsuite/gfortran.dg/goacc/pr93554.f90 b/gcc/testsuite/gfortran.dg/goacc/pr93554.f90
new file mode 100644
index 00000000000..11a27db2623
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/goacc/pr93554.f90
@@ -0,0 +1,21 @@
+! { dg-do compile }
+! { dg-additional-options "-fopenacc" }
+!
+! PR fortran/93554
+! ICE in expand_oacc_for when a derived type with an allocatable
+! component is used with the private clause on an acc loop.
+
+program p
+   type t
+      integer :: a
+      integer, allocatable :: b(:)
+   end type
+   type(t) :: x
+   integer :: i
+   !$acc kernels
+   !$acc loop private(x)
+   do i = 0, 31
+      x%a = 1
+   end do
+   !$acc end kernels
+end
-- 
2.53.0