summaryrefslogtreecommitdiff
path: root/src/lib/libgcc.c
blob: df2325a05a498126a22dc55dbbfa3a9943896bf4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
/* SPDX-License-Identifier: GPL-2.0-only */

#include <types.h>

/*
 * Provide platform-independent backend implementation for __builtin_clz() in
 * <lib.h> in case GCC does not have an assembly version for this arch.
 */

/*
 * FIXME
 * work around lack of --gc-sections on x86
 * defined in rv32 libgcc.a
 */

#if !ENV_X86 && !ENV_RISCV
int __clzsi2(u32 a);
int __clzsi2(u32 a)
{
	static const u8 four_bit_table[] = {
		[0x0] = 4, [0x1] = 3, [0x2] = 2, [0x3] = 2,
		[0x4] = 1, [0x5] = 1, [0x6] = 1, [0x7] = 1,
		[0x8] = 0, [0x9] = 0, [0xa] = 0, [0xb] = 0,
		[0xc] = 0, [0xd] = 0, [0xe] = 0, [0xf] = 0,
	};
	int r = 0;

	if (!(a & (0xffffU << 16))) {
		r += 16;
		a <<= 16;
	}

	if (!(a & (0xffU << 24))) {
		r += 8;
		a <<= 8;
	}

	if (!(a & (0xfU << 28))) {
		r += 4;
		a <<= 4;
	}

	return r + four_bit_table[a >> 28];
}
#endif