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authorAhmad Fatoum <a.fatoum@pengutronix.de>2023-11-22 18:29:39 +0100
committerSascha Hauer <s.hauer@pengutronix.de>2023-11-23 15:50:35 +0100
commitdde1c3e59b88a74a2eb85e9874384936ae20cb57 (patch)
tree06fc76c2535ddae56085ef42b8888d7adb14eef7 /arch/powerpc
parent2376924e24c003def53712d91524f8ffaa6903e7 (diff)
downloadbarebox-dde1c3e59b88a74a2eb85e9874384936ae20cb57.tar.gz
barebox-dde1c3e59b88a74a2eb85e9874384936ae20cb57.tar.xz
include: import Linux word-at-a-time.h
The Linux <linux/word-at-a-time.h> interface is used to optimize searching for bytes in strings by doing word-size comparisons. This will be used in the implementation of strscpy in a follow-up commit, so import the generic version here. A good overview on the interface is available at LWN[1]. Note that it discuss Linux v3.5. The asm-generic version imported here works also on little-endian and not only big-endian[2]. [1]: https://lwn.net/Articles/501492/ [2]: Linux kernel commit a6e2f029ae34 ("Make asm/word-at-a-time.h available on all architectures"). Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de> Link: https://lore.barebox.org/20231122172951.376531-9-a.fatoum@pengutronix.de Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/include/asm/bitops.h1
-rw-r--r--arch/powerpc/include/asm/word-at-a-time.h162
2 files changed, 163 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/bitops.h b/arch/powerpc/include/asm/bitops.h
index 543612e6ed..62b09c7da4 100644
--- a/arch/powerpc/include/asm/bitops.h
+++ b/arch/powerpc/include/asm/bitops.h
@@ -184,6 +184,7 @@ static inline int ffs(int x)
return __ilog2(x & -x) + 1;
}
+#include <asm-generic/bitops/__fls.h>
#include <asm-generic/bitops/fls64.h>
#include <asm-generic/bitops/hweight.h>
diff --git a/arch/powerpc/include/asm/word-at-a-time.h b/arch/powerpc/include/asm/word-at-a-time.h
new file mode 100644
index 0000000000..029740c6de
--- /dev/null
+++ b/arch/powerpc/include/asm/word-at-a-time.h
@@ -0,0 +1,162 @@
+#ifndef _ASM_WORD_AT_A_TIME_H
+#define _ASM_WORD_AT_A_TIME_H
+
+/*
+ * Word-at-a-time interfaces for PowerPC.
+ */
+
+#include <linux/kernel.h>
+#include <linux/bitops.h>
+
+#ifdef __BIG_ENDIAN__
+
+struct word_at_a_time {
+ const unsigned long high_bits, low_bits;
+};
+
+#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0xfe) + 1, REPEAT_BYTE(0x7f) }
+
+/* Bit set in the bytes that have a zero */
+static inline long prep_zero_mask(unsigned long val, unsigned long rhs, const struct word_at_a_time *c)
+{
+ unsigned long mask = (val & c->low_bits) + c->low_bits;
+ return ~(mask | rhs);
+}
+
+#define create_zero_mask(mask) (mask)
+
+static inline long find_zero(unsigned long mask)
+{
+ long leading_zero_bits;
+
+#ifdef __powerpc64__
+ asm ("cntlzd %0,%1" : "=r" (leading_zero_bits) : "r" (mask));
+#else
+ asm ("cntlzw %0,%1" : "=r" (leading_zero_bits) : "r" (mask));
+#endif
+
+ return leading_zero_bits >> 3;
+}
+
+static inline unsigned long has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c)
+{
+ unsigned long rhs = val | c->low_bits;
+ *data = rhs;
+ return (val + c->high_bits) & ~rhs;
+}
+
+static inline unsigned long zero_bytemask(unsigned long mask)
+{
+ return ~1ul << __fls(mask);
+}
+
+#else
+
+#ifdef CONFIG_64BIT
+
+/* unused */
+struct word_at_a_time {
+};
+
+#define WORD_AT_A_TIME_CONSTANTS { }
+
+/* This will give us 0xff for a NULL char and 0x00 elsewhere */
+static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
+{
+ unsigned long ret;
+ unsigned long zero = 0;
+
+ asm("cmpb %0,%1,%2" : "=r" (ret) : "r" (a), "r" (zero));
+ *bits = ret;
+
+ return ret;
+}
+
+static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
+{
+ return bits;
+}
+
+/* Alan Modra's little-endian strlen tail for 64-bit */
+static inline unsigned long create_zero_mask(unsigned long bits)
+{
+ unsigned long leading_zero_bits;
+ long trailing_zero_bit_mask;
+
+ asm("addi %1,%2,-1\n\t"
+ "andc %1,%1,%2\n\t"
+ "popcntd %0,%1"
+ : "=r" (leading_zero_bits), "=&r" (trailing_zero_bit_mask)
+ : "b" (bits));
+
+ return leading_zero_bits;
+}
+
+static inline unsigned long find_zero(unsigned long mask)
+{
+ return mask >> 3;
+}
+
+/* This assumes that we never ask for an all 1s bitmask */
+static inline unsigned long zero_bytemask(unsigned long mask)
+{
+ return (1UL << mask) - 1;
+}
+
+#else /* 32-bit case */
+
+struct word_at_a_time {
+ const unsigned long one_bits, high_bits;
+};
+
+#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
+
+/*
+ * This is largely generic for little-endian machines, but the
+ * optimal byte mask counting is probably going to be something
+ * that is architecture-specific. If you have a reliably fast
+ * bit count instruction, that might be better than the multiply
+ * and shift, for example.
+ */
+
+/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
+static inline long count_masked_bytes(long mask)
+{
+ /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
+ long a = (0x0ff0001+mask) >> 23;
+ /* Fix the 1 for 00 case */
+ return a & mask;
+}
+
+static inline unsigned long create_zero_mask(unsigned long bits)
+{
+ bits = (bits - 1) & ~bits;
+ return bits >> 7;
+}
+
+static inline unsigned long find_zero(unsigned long mask)
+{
+ return count_masked_bytes(mask);
+}
+
+/* Return nonzero if it has a zero */
+static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
+{
+ unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
+ *bits = mask;
+ return mask;
+}
+
+static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
+{
+ return bits;
+}
+
+/* The mask we created is directly usable as a bytemask */
+#define zero_bytemask(mask) (mask)
+
+#endif /* CONFIG_64BIT */
+
+#endif /* __BIG_ENDIAN__ */
+
+#endif /* _ASM_WORD_AT_A_TIME_H */