Provide an optimized implementation of ffs(3) in libc on

aarch64/powerpc/powerpc64, making use of the count leading
zeros instruction.  Also add a brief regression test.
ok deraadt@ kettenis@

2 files changed, 24 insertions, 0 deletions

diff --git a/src/regress/lib/libc/ffs/Makefile b/src/regress/lib/libc/ffs/Makefile
new file mode 100644
index 0000000000..1ad004394f
--- /dev/null
+++ b/src/regress/lib/libc/ffs/Makefile
@@ -0,0 +1,6 @@
+PROG=           ffs_test
+
+# prevent constant folding and inlining of __builtin_ffs()
+CFLAGS+=        -ffreestanding
+
+.include <bsd.regress.mk>
diff --git a/src/regress/lib/libc/ffs/ffs_test.c b/src/regress/lib/libc/ffs/ffs_test.c
new file mode 100644
index 0000000000..bc1e5c53c2
--- /dev/null
+++ b/src/regress/lib/libc/ffs/ffs_test.c
@@ -0,0 +1,18 @@
+/*      $OpenBSD: ffs_test.c,v 1.1 2020/06/26 20:16:22 naddy Exp $ */
+/*
+ * Written by Christian Weisgerber <naddy@openbsd.org>.
+ * Public domain.
+ */
+
+#include <assert.h>
+#include <stdint.h>
+#include <string.h>
+
+int
+main(void)
+{
+        assert(ffs(0) == 0);
+        assert(ffs(0x8080) == 8);
+        assert(ffs(INT32_MIN) == 32);
+        return (0);
+}