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| author | m fally <marlene.fally@gmail.com> | 2025-04-10 13:23:01 +0200 |
|---|---|---|
| committer | Jeff Johnston <jjohnstn@redhat.com> | 2025-04-11 16:47:56 -0400 |
| commit | a9cfc2b8b44e035dbc479a1a9db3e9613699c9b1 (patch) | |
| tree | 50aca7aa976c589efc9dc210aeee67609f06e2ac /newlib | |
| parent | 4a6070a1a0d5433adac9609bae180a95a919122b (diff) | |
| download | newlib-a9cfc2b8b44e035dbc479a1a9db3e9613699c9b1.zip newlib-a9cfc2b8b44e035dbc479a1a9db3e9613699c9b1.tar.gz newlib-a9cfc2b8b44e035dbc479a1a9db3e9613699c9b1.tar.bz2 | |
RISC-V: memmove() size optimized version: Add comments
Since the algorithm in this version of memmove() is different
from the original version, add comments to give a description.
Reviewed-by: Christian Herber <christian.herber@oss.nxp.com>
Reviewed-by: Eric Salem <ericsalem@gmail.com>
Signed-off-by: m fally <marlene.fally@gmail.com>
Diffstat (limited to 'newlib')
| -rw-r--r-- | newlib/libc/machine/riscv/memmove.S | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/newlib/libc/machine/riscv/memmove.S b/newlib/libc/machine/riscv/memmove.S index a77ac44..36fe00e 100644 --- a/newlib/libc/machine/riscv/memmove.S +++ b/newlib/libc/machine/riscv/memmove.S @@ -14,21 +14,21 @@ .global memmove .type memmove, @function memmove: - beqz a2, .Ldone + beqz a2, .Ldone /* in case there are 0 bytes to be copied, return immediately */ - mv a4, 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, .Lcopy + bgtu a1, a0, .Lcopy /* in case of source address > destination address, copy from start to end of the specified memory area */ - li a3, -1 - add a4, a4, a2 - add a1, a1, a2 + li a3, -1 /* otherwhise, we need to start copying from the end of the specified memory area, therefore after each copied byte, increment the addresses by -1 */ + add a4, a4, a2 /* add the number of bytes to be copied to both addresses. this gives an incorrect address, */ + add a1, a1, a2 /* therefore we need to subtract 1 from both addresses in the next step before starting the copying process. */ .Lincrement: - add a4, a4, a3 + 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 .Lcopy: - lb a5, 0(a1) + lb a5, 0(a1) /* copy bytes as long as a2 (= the number of bytes to be copied) > 0 */ sb a5, 0(a4) add a2, a2, -1 bnez a2, .Lincrement |