From a63eafd62de92c089a5132153e10ca8b3e133457 Mon Sep 17 00:00:00 2001
From: Cryolitia PukNgae <cryolitia@gmail.com>
Date: Mon, 14 Oct 2024 01:35:44 +0800
Subject: [PATCH] include: don't use GCC's __builtin_ffs on riscv64

Link: https://github.com/SerenityOS/serenity/commit/e300da4db42e2484d98f4982d03150d83436304e

Signed-off-by: PukNgae Cryolitia <Cryolitia@gmail.com>
---
- cherry-picked
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
---
 include/common/arch/riscv64/asm/bitops.h | 111 ++++++++++++++++++++++-
 1 file changed, 110 insertions(+), 1 deletion(-)

diff --git a/include/common/arch/riscv64/asm/bitops.h b/include/common/arch/riscv64/asm/bitops.h
index 400cc3e155..eabab27c71 100644
--- a/include/common/arch/riscv64/asm/bitops.h
+++ b/include/common/arch/riscv64/asm/bitops.h
@@ -2,7 +2,116 @@
 #define __CR_ASM_BITOPS_H__
 
 #include "common/compiler.h"
-#include "common/asm-generic/bitops.h"
+#include "common/asm/bitsperlong.h"
+
+#define DIV_ROUND_UP(n, d) (((n) + (d)-1) / (d))
+#define BITS_TO_LONGS(nr)  DIV_ROUND_UP(nr, BITS_PER_LONG)
+
+#define DECLARE_BITMAP(name, bits) unsigned long name[BITS_TO_LONGS(bits)]
+#define BITMAP_SIZE(name)	   (sizeof(name) * CHAR_BIT)
+
+#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 1)
+/* Technically wrong, but this avoids compilation errors on some gcc
+   versions. */
+#define BITOP_ADDR(x) "=m"(*(volatile long *)(x))
+#else
+#define BITOP_ADDR(x) "+m"(*(volatile long *)(x))
+#endif
+
+#define ADDR BITOP_ADDR(addr)
+
+static inline void set_bit(int nr, volatile unsigned long *addr)
+{
+	addr += nr / BITS_PER_LONG;
+	*addr |= (1UL << (nr % BITS_PER_LONG));
+}
+
+static inline void change_bit(int nr, volatile unsigned long *addr)
+{
+	addr += nr / BITS_PER_LONG;
+	*addr ^= (1UL << (nr % BITS_PER_LONG));
+}
+
+static inline int test_bit(int nr, volatile const unsigned long *addr)
+{
+	addr += nr / BITS_PER_LONG;
+	return (*addr & (1UL << (nr % BITS_PER_LONG))) ? -1 : 0;
+}
+
+static inline void clear_bit(int nr, volatile unsigned long *addr)
+{
+	addr += nr / BITS_PER_LONG;
+	*addr &= ~(1UL << (nr % BITS_PER_LONG));
+}
+
+/**
+ * __ffs - find first set bit in word
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+static inline unsigned long __ffs(unsigned long word)
+{
+	int p = 0;
+
+	for (; p < 8*sizeof(word); ++p) {
+		if (word & 1) {
+			break;
+		}
+
+		word >>= 1;
+	}
+
+	return p;
+}
+
+#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
+
+/*
+ * Find the next set bit in a memory region.
+ */
+static inline unsigned long find_next_bit(const unsigned long *addr, unsigned long size, unsigned long offset)
+{
+	const unsigned long *p = addr + BITOP_WORD(offset);
+	unsigned long result = offset & ~(BITS_PER_LONG - 1);
+	unsigned long tmp;
+
+	if (offset >= size)
+		return size;
+	size -= result;
+	offset %= BITS_PER_LONG;
+	if (offset) {
+		tmp = *(p++);
+		tmp &= (~0UL << offset);
+		if (size < BITS_PER_LONG)
+			goto found_first;
+		if (tmp)
+			goto found_middle;
+		size -= BITS_PER_LONG;
+		result += BITS_PER_LONG;
+	}
+	while (size & ~(BITS_PER_LONG - 1)) {
+		if ((tmp = *(p++)))
+			goto found_middle;
+		result += BITS_PER_LONG;
+		size -= BITS_PER_LONG;
+	}
+	if (!size)
+		return result;
+	tmp = *p;
+
+found_first:
+	tmp &= (~0UL >> (BITS_PER_LONG - size));
+	if (tmp == 0UL)		      /* Are any bits set? */
+		return result + size; /* Nope. */
+found_middle:
+	return result + __ffs(tmp);
+}
+
+#define for_each_bit(i, bitmask)                                                            \
+	for (i = find_next_bit(bitmask, BITMAP_SIZE(bitmask), 0); i < BITMAP_SIZE(bitmask); \
+	     i = find_next_bit(bitmask, BITMAP_SIZE(bitmask), i + 1))
+
 
 #define BITS_PER_LONG 64