bitint: Don't move debug stmts from before returns_twice calls [PR114628]

Debug stmts are allowed by the verifier before the returns_twice calls.
More importantly, they don't have a lhs, so the current handling of
arg_stmts statements to force them on the edges ICEs.

The following patch just keeps them where they were before.

2024-04-09  Jakub Jelinek  <[email protected]>

	PR middle-end/114628
	* gimple-lower-bitint.cc (gimple_lower_bitint): Keep debug stmts
	before returns_twice calls as is, don't push them into arg_stmts
	vector/move to edges.

	* gcc.dg/bitint-105.c: New test.

Author: jakubjelinek

gcc/gimple-lower-bitint.cc

@@ -7172,8 +7172,13 @@ gimple_lower_bitint (void)
 	  gimple_stmt_iterator gsi = gsi_after_labels (gimple_bb (stmt));
 	  while (gsi_stmt (gsi) != stmt)
 	    {
-	      arg_stmts.safe_push (gsi_stmt (gsi));
-	      gsi_remove (&gsi, false);
+	      if (is_gimple_debug (gsi_stmt (gsi)))
+		gsi_next (&gsi);
+	      else
+		{
+		  arg_stmts.safe_push (gsi_stmt (gsi));
+		  gsi_remove (&gsi, false);
+		}
 	    }
 	  gimple *g;
 	  basic_block bb = NULL;

gcc/testsuite/gcc.dg/bitint-105.c

@@ -0,0 +1,29 @@
+/* PR middle-end/114628 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-O2 -g" } */
+
+int foo (int);
+#if __BITINT_MAXWIDTH__ >= 129
+__attribute__((returns_twice)) int bar (_BitInt(129) x);
+
+void
+baz (int x, _BitInt(129) y)
+{
+  void *q[] = { &&l1, &&l2 };
+l2:
+  x = foo (foo (3));
+  bar (y);
+  goto *q[x & 1];
+l1:;
+}
+
+void
+qux (int x, _BitInt(129) y)
+{
+  void *q[] = { &&l1, &&l2 };
+l2:
+  x = foo (foo (3));
+  bar (y);
+l1:;
+}
+#endif