[PATCH v3 next 06/10] lib: test_mul_u64_u64_div_u64: Test both generic and arch versions

[David Laight]

Change the #if in div64.c so that test_mul_u64_u64_div_u64.c
can compile and test the generic version (including the 'long multiply')
on architectures (eg amd64) that define their own copy.

Test the kernel version and the locally compiled version on all arch.
Output the time taken (in ns) on the 'test completed' trace.

For reference, on my zen 5, the optimised version takes ~220ns and the
generic version ~3350ns.
Using the native multiply saves ~200ns and adding back the ilog2() 'optimisation'
test adds ~50ms.

Signed-off-by: David Laight <david.laight.linux@xxxxxxxxx>
---

New patch for v3, replacing changes in v1 that were removed for v2.

 lib/math/div64.c                    |  8 +++--
 lib/math/test_mul_u64_u64_div_u64.c | 48 ++++++++++++++++++++++++-----
 2 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/lib/math/div64.c b/lib/math/div64.c
index 7850cc0a7596..22433e5565c4 100644
--- a/lib/math/div64.c
+++ b/lib/math/div64.c
@@ -178,13 +178,15 @@ EXPORT_SYMBOL(div64_s64);
  * Iterative div/mod for use when dividend is not expected to be much
  * bigger than divisor.
  */
+#ifndef iter_div_u64_rem
 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
 {
 	return __iter_div_u64_rem(dividend, divisor, remainder);
 }
 EXPORT_SYMBOL(iter_div_u64_rem);
+#endif
 
-#ifndef mul_u64_add_u64_div_u64
+#if !defined(mul_u64_add_u64_div_u64) || defined(test_mul_u64_add_u64_div_u64)
 u64 mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d)
 {
 	if (WARN_ONCE(!d, "%s: division of (%#llx * %#llx + %#llx) by zero, returning 0",
@@ -196,7 +198,7 @@ u64 mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d)
 		return 0;
 	}
 
-#if defined(__SIZEOF_INT128__)
+#if defined(__SIZEOF_INT128__) && !defined(test_mul_u64_add_u64_div_u64)
 
 	/* native 64x64=128 bits multiplication */
 	u128 prod = (u128)a * b + c;
@@ -270,5 +272,7 @@ u64 mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d)
 
 	return res;
 }
+#if !defined(test_mul_u64_add_u64_div_u64)
 EXPORT_SYMBOL(mul_u64_add_u64_div_u64);
 #endif
+#endif
diff --git a/lib/math/test_mul_u64_u64_div_u64.c b/lib/math/test_mul_u64_u64_div_u64.c
index ea5b703cccff..f0134f25cb0d 100644
--- a/lib/math/test_mul_u64_u64_div_u64.c
+++ b/lib/math/test_mul_u64_u64_div_u64.c
@@ -73,21 +73,34 @@ done
 
  */
 
-static int __init test_init(void)
+static u64 test_mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d);
+
+static int __init test_run(unsigned int fn_no, const char *fn_name)
 {
+	u64 start_time;
 	int errors = 0;
 	int tests = 0;
 	int i;
 
-	pr_info("Starting mul_u64_u64_div_u64() test\n");
+	start_time = ktime_get_ns();
 
 	for (i = 0; i < ARRAY_SIZE(test_values); i++) {
 		u64 a = test_values[i].a;
 		u64 b = test_values[i].b;
 		u64 d = test_values[i].d;
 		u64 expected_result = test_values[i].result;
-		u64 result = mul_u64_u64_div_u64(a, b, d);
-		u64 result_up = mul_u64_u64_div_u64_roundup(a, b, d);
+		u64 result, result_up;
+
+		switch (fn_no) {
+		default:
+			result = mul_u64_u64_div_u64(a, b, d);
+			result_up = mul_u64_u64_div_u64_roundup(a, b, d);
+			break;
+		case 1:
+			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;
+		}
 
 		tests += 2;
 
@@ -106,15 +119,36 @@ static int __init test_init(void)
 		}
 	}
 
-	pr_info("Completed mul_u64_u64_div_u64() test, %d tests, %d errors\n",
-		tests, errors);
-	return errors ? -EINVAL : 0;
+	pr_info("Completed %s() test, %d tests, %d errors, %llu ns\n",
+		fn_name, tests, errors, ktime_get_ns() - start_time);
+	return errors;
+}
+
+static int __init test_init(void)
+{
+	pr_info("Starting mul_u64_u64_div_u64() test\n");
+	if (test_run(0, "mul_u64_u64_div_u64"))
+		return -EINVAL;
+	if (test_run(1, "test_mul_u64_u64_div_u64"))
+		return -EINVAL;
+	return 0;
 }
 
 static void __exit test_exit(void)
 {
 }
 
+/* Compile the generic mul_u64_add_u64_div_u64() code */
+#define div64_u64 div64_u64
+#define div64_s64 div64_s64
+#define iter_div_u64_rem iter_div_u64_rem
+
+#undef mul_u64_add_u64_div_u64
+#define mul_u64_add_u64_div_u64 test_mul_u64_add_u64_div_u64
+#define test_mul_u64_add_u64_div_u64 test_mul_u64_add_u64_div_u64
+
+#include "div64.c"
+
 module_init(test_init);
 module_exit(test_exit);
 
-- 
2.39.5