1 files changed, 71 insertions, 0 deletions
diff --git a/lib/libc/stdbit/stdc_bit_ceil.c b/lib/libc/stdbit/stdc_bit_ceil.c
new file mode 100644
index 000000000000..2dfd7bbcbea2
--- /dev/null
+++ b/lib/libc/stdbit/stdc_bit_ceil.c
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <assert.h>
+#include <limits.h>
+#include <stdbit.h>
+
+/* Ensure we don't shift 1U out of range. */
+static_assert(UCHAR_WIDTH < UINT_WIDTH,
+    "stdc_bit_ceil_uc needs UCHAR_WIDTH < UINT_WIDTH");
+
+unsigned char
+stdc_bit_ceil_uc(unsigned char x)
+{
+	if (x <= 1)
+		return (1);
+
+	return (1U << (UINT_WIDTH - __builtin_clz(x - 1)));
+}
+
+/* Ensure we don't shift 1U out of range. */
+static_assert(USHRT_WIDTH < UINT_WIDTH,
+    "stdc_bit_ceil_us needs USHRT_WIDTH < UINT_WIDTH");
+
+unsigned short
+stdc_bit_ceil_us(unsigned short x)
+{
+	if (x <= 1)
+		return (1);
+
+	return (1U << (UINT_WIDTH - __builtin_clz(x - 1)));
+}
+
+unsigned int
+stdc_bit_ceil_ui(unsigned int x)
+{
+	if (x <= 1)
+		return (1);
+
+	if (x > UINT_MAX/2 + 1)
+		return (0);
+
+	return (1U << (UINT_WIDTH - __builtin_clz(x - 1)));
+}
+
+unsigned long
+stdc_bit_ceil_ul(unsigned long x)
+{
+	if (x <= 1)
+		return (1);
+
+	if (x > ULONG_MAX/2 + 1)
+		return (0);
+
+	return (1UL << (ULONG_WIDTH - __builtin_clzl(x - 1)));
+}
+
+unsigned long long
+stdc_bit_ceil_ull(unsigned long long x)
+{
+	if (x <= 1)
+		return (1);
+
+	if (x > ULLONG_MAX/2 + 1)
+		return (0);
+
+	return (1ULL << (ULLONG_WIDTH - __builtin_clzll(x - 1)));
+}