lib: test_mul_u64_u64_div_u64(): test the 32bit code on 64bit

There are slight differences in the mul_u64_add_u64_div_u64() code between
32bit and 64bit systems.

Compile and test the 32bit version on 64bit hosts for better test
coverage.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: David Laight <[e-mail]>
Reviewed-by: Nicolas Pitre <[e-mail]>
Cc: Biju Das <[e-mail]>
Cc: Borislav Betkov <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Li RongQing <[e-mail]>
Cc: Oleg Nesterov <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleinxer <[e-mail]>
Cc: Uwe Kleine-König <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

lib/math/test_mul_u64_u64_div_u64.c

···
  */
 
 static u64 test_mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d);
+#if __LONG_WIDTH__ >= 64
+#define TEST_32BIT_DIV
+static u64 test_mul_u64_add_u64_div_u64_32bit(u64 a, u64 b, u64 c, u64 d);
+#endif
 
 static int __init test_run(unsigned int fn_no, const char *fn_name)
 {
···
 			result = test_mul_u64_add_u64_div_u64(a, b, 0, d);
 			result_up = test_mul_u64_add_u64_div_u64(a, b, d - 1, d);
 			break;
+#ifdef TEST_32BIT_DIV
+		case 2:
+			result = test_mul_u64_add_u64_div_u64_32bit(a, b, 0, d);
+			result_up = test_mul_u64_add_u64_div_u64_32bit(a, b, d - 1, d);
+			break;
+#endif
 		}
 
 		tests += 2;
···
 		return -EINVAL;
 	if (test_run(1, "test_mul_u64_u64_div_u64"))
 		return -EINVAL;
+#ifdef TEST_32BIT_DIV
+	if (test_run(2, "test_mul_u64_u64_div_u64_32bit"))
+		return -EINVAL;
+#endif
 	return 0;
 }
 
···
 #define test_mul_u64_add_u64_div_u64 test_mul_u64_add_u64_div_u64
 
 #include "div64.c"
+
+#ifdef TEST_32BIT_DIV
+/* Recompile the generic code for 32bit long */
+#undef test_mul_u64_add_u64_div_u64
+#define test_mul_u64_add_u64_div_u64 test_mul_u64_add_u64_div_u64_32bit
+#undef BITS_PER_ITER
+#define BITS_PER_ITER 16
+
+#define mul_u64_u64_add_u64 mul_u64_u64_add_u64_32bit
+#undef mul_u64_long_add_u64
+#undef add_u64_long
+#undef mul_add
+
+#include "div64.c"
+#endif
 
 module_init(test_init);
 module_exit(test_exit);