lib: Fix log2_ceil() for 0xffffffff

Current log2_ceil(x) is defined as log2(x * 2 - 1). When x is larger
than (1 << 31), (x * 2 - 1) won't fit in u32, leading to incorrect
result. Therefore, correct it as (log2(x - 1) + 1). Also add unit tests
for inline functions in lib.h.

BUG=none
TEST=make tests/lib/lib-test
BRANCH=none

Change-Id: If868f793b909a6ad7fc48a7affac15e2c714fa2e
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59834
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>

src/include/lib.h

@@ -54,8 +54,8 @@ static inline int log2(u32 x) { return sizeof(x) * 8 - clz(x) - 1; }
 /* Find First Set: __ffs(1) == 0, __ffs(0) == -1, __ffs(1<<31) == 31 */
 static inline int __ffs(u32 x) { return log2(x & (u32)(-(s32)x)); }
 
-/* Integer binary logarithm (rounding up): log2_ceil(0) == -1, log2(5) == 3 */
+/* Integer binary logarithm (rounding up): log2_ceil(0) == -1, log2_ceil(5) == 3 */
-static inline int log2_ceil(u32 x) { return (x == 0) ? -1 : log2(x * 2 - 1); }
+static inline int log2_ceil(u32 x) { return (x == 0) ? -1 : log2(x - 1) + 1; }
 
 static inline int popcnt64(u64 x) { return __builtin_popcountll(x); }
 static inline int clz64(u64 x) { return x ? __builtin_clzll(x) : sizeof(x) * 8; }

tests/lib/Makefile.inc

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
+tests-y += lib-test
 tests-y += string-test
 tests-y += b64_decode-test
 tests-y += hexstrtobin-test
@@ -40,6 +41,8 @@ tests-y += cbfs-lookup-no-mcache-test
 tests-y += cbfs-lookup-has-mcache-test
 tests-y += lzma-test
 
+lib-test-srcs += tests/lib/lib-test.c
+
 string-test-srcs += tests/lib/string-test.c
 string-test-srcs += src/lib/string.c
 

tests/lib/lib-test.c

@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <lib.h>
+#include <tests/test.h>
+
+void test_popcnt(void **state)
+{
+	assert_int_equal(popcnt(0x0), 0);
+	assert_int_equal(popcnt(0x10), 1);
+	assert_int_equal(popcnt(0x10010010), 3);
+	assert_int_equal(popcnt(0xffffffff), 32);
+}
+
+void test_clz(void **state)
+{
+	assert_int_equal(clz(0x0), 32);
+	assert_int_equal(clz(0xf), 28);
+	assert_int_equal(clz(0x80000000), 0);
+	assert_int_equal(clz(0xffffffff), 0);
+}
+
+void test_log2(void **state)
+{
+	assert_int_equal(log2(0x0), -1);
+	assert_int_equal(log2(0x1), 0);
+	assert_int_equal(log2(0x5), 2);
+	assert_int_equal(log2(0x80000000), 31);
+	assert_int_equal(log2(0xffffffff), 31);
+}
+
+void test_ffs(void **state)
+{
+	assert_int_equal(__ffs(0x0), -1);
+	assert_int_equal(__ffs(0x1), 0);
+	assert_int_equal(__ffs(0x1010), 4);
+	assert_int_equal(__ffs(0x10000000), 28);
+	assert_int_equal(__ffs(0xffffffff), 0);
+}
+
+void test_log2_ceil(void **state)
+{
+	assert_int_equal(log2_ceil(0x0), -1);
+	assert_int_equal(log2_ceil(0x1), 0);
+	assert_int_equal(log2_ceil(0x5), 3);
+	assert_int_equal(log2_ceil(0x80000000), 31);
+	assert_int_equal(log2_ceil(0xffffffff), 32);
+}
+
+int main(void)
+{
+	const struct CMUnitTest tests[] = {
+		cmocka_unit_test(test_popcnt),
+		cmocka_unit_test(test_clz),
+		cmocka_unit_test(test_log2),
+		cmocka_unit_test(test_ffs),
+		cmocka_unit_test(test_log2_ceil),
+	};
+
+	return cb_run_group_tests(tests, NULL, NULL);
+}