1 files changed, 128 insertions, 0 deletions
diff --git a/roms/u-boot/arch/riscv/lib/memmove.S b/roms/u-boot/arch/riscv/lib/memmove.S
new file mode 100644
index 000000000..fbe6701db
--- /dev/null
+++ b/roms/u-boot/arch/riscv/lib/memmove.S
@@ -0,0 +1,128 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+
+ENTRY(__memmove)
+WEAK(memmove)
+	/*
+	 * Here we determine if forward copy is possible. Forward copy is
+	 * preferred to backward copy as it is more cache friendly.
+	 *
+	 * If a0 >= a1, t0 gives their distance, if t0 >= a2 then we can
+	 *   copy forward.
+	 * If a0 < a1, we can always copy forward. This will make t0 negative,
+	 *   so a *unsigned* comparison will always have t0 >= a2.
+	 *
+	 * For forward copy we just delegate the task to memcpy.
+	 */
+	sub	t0, a0, a1
+	bltu	t0, a2, 1f
+	tail	__memcpy
+1:
+
+	/*
+	 * Register allocation for code below:
+	 * a0 - end of uncopied dst
+	 * a1 - end of uncopied src
+	 * t0 - start of uncopied dst
+	 */
+	mv	t0, a0
+	add	a0, a0, a2
+	add	a1, a1, a2
+
+	/*
+	 * Use bytewise copy if too small.
+	 *
+	 * This threshold must be at least 2*SZREG to ensure at least one
+	 * wordwise copy is performed. It is chosen to be 16 because it will
+	 * save at least 7 iterations of bytewise copy, which pays off the
+	 * fixed overhead.
+	 */
+	li	a3, 16
+	bltu	a2, a3, .Lbyte_copy_tail
+
+	/*
+	 * Bytewise copy first to align t0 to word boundary.
+	 */
+	andi	a2, a0, ~(SZREG-1)
+	beq	a0, a2, 2f
+1:
+	addi	a1, a1, -1
+	lb	a5, 0(a1)
+	addi	a0, a0, -1
+	sb	a5, 0(a0)
+	bne	a0, a2, 1b
+2:
+
+	/*
+	 * Now a0 is word-aligned. If a1 is also word aligned, we could perform
+	 * aligned word-wise copy. Otherwise we need to perform misaligned
+	 * word-wise copy.
+	 */
+	andi	a3, a1, SZREG-1
+	bnez	a3, .Lmisaligned_word_copy
+
+	/* Wordwise copy */
+	addi	t0, t0, SZREG-1
+	bleu	a0, t0, 2f
+1:
+	addi	a1, a1, -SZREG
+	REG_L	a5, 0(a1)
+	addi	a0, a0, -SZREG
+	REG_S	a5, 0(a0)
+	bgtu	a0, t0, 1b
+2:
+	addi	t0, t0, -(SZREG-1)
+
+.Lbyte_copy_tail:
+	/*
+	 * Bytewise copy anything left.
+	 */
+	beq	a0, t0, 2f
+1:
+	addi	a1, a1, -1
+	lb	a5, 0(a1)
+	addi	a0, a0, -1
+	sb	a5, 0(a0)
+	bne	a0, t0, 1b
+2:
+
+	mv	a0, t0
+	ret
+
+.Lmisaligned_word_copy:
+	/*
+	 * Misaligned word-wise copy.
+	 * For misaligned copy we still perform word-wise copy, but we need to
+	 * use the value fetched from the previous iteration and do some shifts.
+	 * This is safe because we wouldn't access more words than necessary.
+	 */
+
+	/* Calculate shifts */
+	slli	t3, a3, 3
+	sub	t4, x0, t3 /* negate is okay as shift will only look at LSBs */
+
+	/* Load the initial value and align a1 */
+	andi	a1, a1, ~(SZREG-1)
+	REG_L	a5, 0(a1)
+
+	addi	t0, t0, SZREG-1
+	/* At least one iteration will be executed here, no check */
+1:
+	sll	a4, a5, t4
+	addi	a1, a1, -SZREG
+	REG_L	a5, 0(a1)
+	srl	a2, a5, t3
+	or	a2, a2, a4
+	addi	a0, a0, -SZREG
+	REG_S	a2, 0(a0)
+	bgtu	a0, t0, 1b
+
+	/* Update pointers to correct value */
+	addi	t0, t0, -(SZREG-1)
+	add	a1, a1, a3
+
+	j	.Lbyte_copy_tail
+
+END(__memmove)