From 909c317b2deb184d95c7d289cbe6603e209ed72d Mon Sep 17 00:00:00 2001
From: Yidi Lin <yidilin@chromium.org>
Date: Tue, 31 Oct 2023 14:57:04 +0800
Subject: commonlib: Add GCD function

Implement a simple GCD function.

BUG=b:307790895
TEST=emerge-geralt coreboot
TEST=make tests/commonlib/bsd/gcd-test

Change-Id: I21819cda4299b3809b8ca7a95cbdc6a87e4b3481
Signed-off-by: Yidi Lin <yidilin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78798
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
---
 src/commonlib/Makefile.inc                    |  3 +++
 src/commonlib/bsd/gcd.c                       | 23 +++++++++++++++++++++++
 src/commonlib/bsd/include/commonlib/bsd/gcd.h | 10 ++++++++++
 tests/commonlib/bsd/Makefile.inc              |  4 ++++
 tests/commonlib/bsd/gcd-test.c                | 27 +++++++++++++++++++++++++++
 5 files changed, 67 insertions(+)
 create mode 100644 src/commonlib/bsd/gcd.c
 create mode 100644 src/commonlib/bsd/include/commonlib/bsd/gcd.h
 create mode 100644 tests/commonlib/bsd/gcd-test.c

diff --git a/src/commonlib/Makefile.inc b/src/commonlib/Makefile.inc
index 86e8c5695ca0..70e731df354d 100644
--- a/src/commonlib/Makefile.inc
+++ b/src/commonlib/Makefile.inc
@@ -58,3 +58,6 @@ ramstage-y += sort.c
 romstage-y += bsd/elog.c
 ramstage-y += bsd/elog.c
 smm-y += bsd/elog.c
+
+decompressor-y += bsd/gcd.c
+all-y += bsd/gcd.c
diff --git a/src/commonlib/bsd/gcd.c b/src/commonlib/bsd/gcd.c
new file mode 100644
index 000000000000..92b601e8d01d
--- /dev/null
+++ b/src/commonlib/bsd/gcd.c
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+#include <commonlib/bsd/gcd.h>
+#include <commonlib/bsd/helpers.h>
+#include <stdint.h>
+
+uint32_t gcd32(uint32_t a, uint32_t b)
+{
+	uint32_t c;
+
+	if (a == 0 || b == 0)
+		return MAX(a, b);
+
+	c = a % b;
+
+	while (c > 0) {
+		a = b;
+		b = c;
+		c = a % b;
+	}
+
+	return b;
+}
diff --git a/src/commonlib/bsd/include/commonlib/bsd/gcd.h b/src/commonlib/bsd/include/commonlib/bsd/gcd.h
new file mode 100644
index 000000000000..20949ded09df
--- /dev/null
+++ b/src/commonlib/bsd/include/commonlib/bsd/gcd.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+#ifndef _COMMONLIB_BSD_GCD_H_
+#define _COMMONLIB_BSD_GCD_H_
+
+#include <stdint.h>
+
+uint32_t gcd32(uint32_t a, uint32_t b);
+
+#endif /* _COMMONLIB_BSD_GCD_H_ */
diff --git a/tests/commonlib/bsd/Makefile.inc b/tests/commonlib/bsd/Makefile.inc
index 56664d037cc2..bf17b6d56dbb 100644
--- a/tests/commonlib/bsd/Makefile.inc
+++ b/tests/commonlib/bsd/Makefile.inc
@@ -1,5 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 tests-y += helpers-test
+tests-y += gcd-test
 
 helpers-test-srcs += tests/commonlib/bsd/helpers-test.c
+
+gcd-test-srcs += tests/commonlib/bsd/gcd-test.c
+gcd-test-srcs += src/commonlib/bsd/gcd.c
diff --git a/tests/commonlib/bsd/gcd-test.c b/tests/commonlib/bsd/gcd-test.c
new file mode 100644
index 000000000000..13fad86ec405
--- /dev/null
+++ b/tests/commonlib/bsd/gcd-test.c
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <commonlib/bsd/gcd.h>
+#include <tests/test.h>
+
+static void test_gcd32(void **state)
+{
+	assert_int_equal(gcd32(17, 11), 1);
+	assert_int_equal(gcd32(64, 36), 4);
+	assert_int_equal(gcd32(90, 123), 3);
+	assert_int_equal(gcd32(65536, 339584), 128);
+	assert_int_equal(gcd32(1, 1), 1);
+	assert_int_equal(gcd32(1, 123), 1);
+	assert_int_equal(gcd32(123, 1), 1);
+	assert_int_equal(gcd32(1, UINT32_MAX), 1);
+	assert_int_equal(gcd32(UINT32_MAX, 1), 1);
+	assert_int_equal(gcd32(UINT32_MAX, UINT32_MAX), UINT32_MAX);
+}
+
+int main(void)
+{
+	const struct CMUnitTest tests[] = {
+		cmocka_unit_test(test_gcd32),
+	};
+
+	return cb_run_group_tests(tests, NULL, NULL);
+}
-- 
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