Fix ICE in verify_sra_access_forest

This fixes an issue with reverse storage order in SRA, which is caught
by the built-in verifier in verify_sra_access_forest.  The problem is
that propagate_subaccesses_from_rhs changes the type of an access
from aggregate to scalar and, as discussed elsewhere, this must be
done with extra care in the presence of reverse storage order.

gcc/ChangeLog
	* tree-sra.c (propagate_subaccesses_from_rhs): When a non-scalar
	access on the LHS is replaced with a scalar access, propagate the
	TYPE_REVERSE_STORAGE_ORDER flag of the type of the original access.

gcc/testsuite/ChangeLog
	* gnat.dg/opt85.ads, gnat.dg/opt85.adb: New test.

1 files changed, 6 insertions, 0 deletions

diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 4793b48..fcba7fb 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -2758,6 +2758,9 @@ propagate_subaccesses_from_rhs (struct access *lacc, struct access *racc)
 	}
       if (!lacc->first_child && !racc->first_child)
 	{
+	  /* We are about to change the access type from aggregate to scalar,
+	     so we need to put the reverse flag onto the access, if any.  */
+	  const bool reverse = TYPE_REVERSE_STORAGE_ORDER (lacc->type);
 	  tree t = lacc->base;
 
 	  lacc->type = racc->type;
@@ -2772,9 +2775,12 @@ propagate_subaccesses_from_rhs (struct access *lacc, struct access *racc)
 	      lacc->expr = build_ref_for_model (EXPR_LOCATION (lacc->base),
 						lacc->base, lacc->offset,
 						racc, NULL, false);
+	      if (TREE_CODE (lacc->expr) == MEM_REF)
+		REF_REVERSE_STORAGE_ORDER (lacc->expr) = reverse;
 	      lacc->grp_no_warning = true;
 	      lacc->grp_same_access_path = false;
 	    }
+	  lacc->reverse = reverse;
 	}
       return ret;
     }