diff options
Diffstat (limited to 'newlib/libc/machine/riscv/memmove.S')
| -rw-r--r-- | newlib/libc/machine/riscv/memmove.S | 28 |
1 files changed, 14 insertions, 14 deletions
diff --git a/newlib/libc/machine/riscv/memmove.S b/newlib/libc/machine/riscv/memmove.S index 66d9cd4..061472c 100644 --- a/newlib/libc/machine/riscv/memmove.S +++ b/newlib/libc/machine/riscv/memmove.S @@ -14,26 +14,26 @@ .global memmove .type memmove, @function memmove: - beqz a2, 2f + beqz a2, .Ldone /* in case there are 0 bytes to be copied, return immediately */ - mv t1, a0 + mv a4, a0 /* copy the destination address over to a4, since memmove should return that address in a0 at the end */ li a3, 1 - bgtu a1, a0, 1f + bgtu a1, a0, .Lcopy /* in case of source address > destination address, copy from start to end of the specified memory area */ - li a3, -1 - addi a4, a2 , -1 - add t1, t1, a4 - add a1, a1, a4 + li a3, -1 /* otherwhise, start copying from the end of the specified memory area in order to prevent data loss in case of overlapping memory areas.*/ + add a4, a4, a2 /* add the number of bytes to be copied to both addresses. this gives us the address one byte past the end of the memory area we want to copy, */ + add a1, a1, a2 /* therefore we need to subtract 1 from both addresses in the next step before starting the copying process. */ -1: - lb t2, 0(a1) - sb t2, 0(t1) - add a2, a2, -1 - add t1, t1, a3 +.Lincrement: + add a4, a4, a3 /* in case of source address < destination address, increment both addresses by -1 before copying any data to obtain the correct start addresses */ add a1, a1, a3 - bnez a2, 1b +.Lcopy: + lbu a5, 0(a1) + addi a2, a2, -1 /* copy bytes as long as a2 (= the number of bytes to be copied) > 0. the increment is done here to relax the RAW dependency between load and store */ + sb a5, 0(a4) + bnez a2, .Lincrement -2: +.Ldone: ret .size memmove, .-memmove |