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Opt memcpy memmove #682

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a9eb558
removed unused mempcpy variant
ZERICO2005 Jan 5, 2026
b7e70a0
optimized zero size test in memcpy/memmove
ZERICO2005 Jan 5, 2026
030932f
added memcpy/memmove tests for non-zero multiples of 65536
ZERICO2005 Jan 5, 2026
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31 changes: 22 additions & 9 deletions src/libc/memcpy.src
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Expand Up @@ -12,17 +12,30 @@
.else

_memcpy:
ld iy, -1
; size > 0 : 25F + 15R + 1 + LDIR
; size >= 65536 : 32F + 16R + 3 + LDIR
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@calc84maniac calc84maniac Jan 7, 2026

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This comment is no longer applicable, right?

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@ZERICO2005 ZERICO2005 Jan 7, 2026

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Yeah, I will fix that

; size == 0 : 26F + 13R + 2
; size >= 65536 + 7F + 1R + 2 (only when the low 16 bits are zero)

ld iy, 0
add iy, sp
ld bc, (iy + 10) ; Load count
sbc hl, hl
add hl, bc
jr nc, .L.zero
ld de, (iy + 4) ; Load destination
ld hl, (iy + 7) ; Load source
ld bc, (iy + 9) ; Load count
ld a, c
or a, b
ld de, (iy + 3) ; Load destination
jr z, .L.maybe_zero
.L.not_zero:
ld hl, (iy + 6) ; Load source
ldir
.L.zero:
ld hl, (iy + 4) ; Return the destination pointer
ld hl, (iy + 3) ; Return the destination pointer
ret

.L.maybe_zero:
; low 16 bits are zero
or a, (iy + 11) ; test upper 8 bits
jr nz, .L.not_zero ; size >= 65536
; size == 0
ex de, hl
ret

.endif
108 changes: 62 additions & 46 deletions src/libc/memmove.src
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Expand Up @@ -15,87 +15,103 @@

; Optimized for when src != dst
_memmove:
; src > dst | LDIR | 32F + 15R + 1
; src < dst | LDDR | 35F + 12R + 2
; src = dst | LDDR | 35F + 12R + 2
; zero size | | 24F + 12R + 2
; src > dst | LDIR | 31F + 15R + 2
; src < dst | LDDR | 33F + 12R + 1
; src = dst | LDIR | 31F + 15R + 2
; zero size | | 26F + 10R + 2
; size >= 65536 + 7F + 1R + 2 (only when the low 16 bits are zero)

ld iy, -1
ld iy, 0
add iy, sp
ld bc, (iy + 10)
sbc hl, hl
add hl, bc
jr nc, .L.zero
ld hl, (iy + 7)
ld de, (iy + 4)
ld bc, (iy + 9)
ld a, c
or a, b
ld de, (iy + 3)
jr z, .L.maybe_zero
.L.not_zero:
ld hl, (iy + 6)
sbc hl, de
; src <= dst
jr c, .L.copy_backwards
; src > dst
; .copy_forwards:
add hl, de
inc hl
ldir
.L.zero:
ld hl, (iy + 4)
ret

.L.copy_backwards:
; src >= dst
jr nc, .L.copy_forwards
; src < dst
; .L.copy_backwards:
; move HL and DE to the end
dec de ; DE = dst - 1
ex de, hl
add hl, bc ; HL = dst + size - 1, DE = src - dst
ex de, hl
add hl, bc
ex de, hl ; HL = src - dst - 1, DE = dst + size
add hl, de ; HL = src + size - 1
dec de ; DE = dst + size - 1
add hl, de ; HL = src + size - 1, DE = dst + size - 1
lddr
ex de, hl
inc hl
ret

.L.copy_forwards:
add hl, de
ldir
ld hl, (iy + 3)
ret

.L.maybe_zero:
; low 16 bits are zero
or a, (iy + 11) ; test upper 8 bits
jr nz, .L.not_zero ; size >= 65536
; size == 0
ex de, hl
ret

.else

; Optimized for when src == dst
_memmove:
; src > dst | LDIR | 33F + 15R + 2
; src < dst | LDDR | 36F + 12R + 2
; src = dst | | 29F + 12R + 2
; zero size | | 24F + 12R + 2
; src > dst | LDIR | 31F + 15R + 2
; src < dst | LDDR | 34F + 12R + 2
; src = dst | | 27F + 12R + 2
; zero size | | 26F + 10R + 2
; size >= 65536 + 7F + 1R + 2 (only when the low 16 bits are zero)

ld iy, -1
ld iy, 0
add iy, sp
ld bc, (iy + 10)
sbc hl, hl
add hl, bc
jr nc, .L.zero
ld de, (iy + 4)
ld hl, (iy + 7)
or a, a
ld bc, (iy + 9)
ld a, c
or a, b
ld de, (iy + 3)
jr z, .L.maybe_zero
.L.not_zero:
ld hl, (iy + 6)
sbc hl, de
; src < dst
jr c, .copy_backwards
jr c, .L.copy_backwards
; src >= dst
; .L.copy_forwards:
add hl, de
; src == dst
ret z ; skips LDIR when src == dst
ret z ; skips LDIR when src == dst
; src > dst
ldir
.L.zero:
ld hl, (iy + 4)
ld hl, (iy + 3)
ret

.L.copy_backwards:
; move HL and DE to the end
dec de ; DE = dst - 1
dec de ; DE = dst - 1
ex de, hl
add hl, bc ; HL = dst + size - 1, DE = src - dst
add hl, bc ; HL = dst + size - 1, DE = src - dst
ex de, hl
add hl, de ; HL = src + size - 1, DE = dst + size - 1
add hl, de ; HL = src + size - 1, DE = dst + size - 1
lddr
ex de, hl
inc hl
ret

.L.maybe_zero:
; low 16 bits are zero
or a, (iy + 11) ; test upper 8 bits
jr nz, .L.not_zero ; size >= 65536
; size == 0
ex de, hl
ret

.endif

.endif
22 changes: 0 additions & 22 deletions src/libc/mempcpy.src
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Expand Up @@ -5,26 +5,6 @@
.global _mempcpy
.type _mempcpy, @function

.if 0

; faster when count is zero
_mempcpy:
ld iy, -1
add iy, sp
ld bc, (iy + 10) ; Load count
sbc hl, hl
add hl, bc
ld hl, (iy + 4) ; Load destination
ret nc ; zero bytes to copy
ld de, (iy + 7) ; Load source
ex de, hl
ldir
ex de, hl
ret

.else

; faster in full execution case by 0F + 1 clock cycles
_mempcpy:
ld iy, -1
add iy, sp
Expand All @@ -38,5 +18,3 @@ _mempcpy:
.L.zero_byte_copy:
ex de, hl
ret

.endif
26 changes: 26 additions & 0 deletions test/standalone/asprintf_fprintf/src/fill_mem32.s
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@@ -0,0 +1,26 @@
.assume adl = 1

.section .text

.global _fill_mem32

; void fill_mem32(void *dst, size_t bytes, uint32_t pattern)
_fill_mem32:
ld iy, 0
add iy, sp
ld de, (iy + 3)
ld hl, (iy + 6)
ld bc, 4
sbc hl, bc
; return if bytes <= pattern_size
ret c
ret z
push hl
; copy pattern once
lea hl, iy + 9
ldir
pop bc
; now copy (bytes - pattern_size)
ld hl, (iy + 3)
ldir
ret
55 changes: 55 additions & 0 deletions test/standalone/asprintf_fprintf/src/main.c
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Expand Up @@ -49,6 +49,9 @@ void *T_memccpy(void *__restrict dest, const void *__restrict src, int c, size_t
void *T_mempcpy(void *__restrict dest, const void *__restrict src, size_t n)
__attribute__((nonnull(1, 2)));

void *T_memchr(const void *s, int c, size_t n)
__attribute__((nonnull(1)));

void *T_memrchr(const void *s, int c, size_t n)
__attribute__((nonnull(1)));

Expand Down Expand Up @@ -92,6 +95,7 @@ void T_bzero(void* s, size_t n);
#define T_memcmp memcmp
#define T_memccpy memccpy
#define T_mempcpy mempcpy
#define T_memchr memchr
#define T_memrchr memrchr
#define T_memmem memmem
#define T_memrmem memrmem
Expand Down Expand Up @@ -994,6 +998,54 @@ int strchrnul_test(void) {
return 0;
}

int mem65536_test(void) {
void fill_mem32(void *dst, size_t bytes, uint32_t pattern);

uint8_t * const dst = (uint8_t*)0xD40000;
const size_t screen_size = 320 * 240 * 2;
memset(dst, 0, screen_size);
const size_t B16 = 65536;
const size_t B17 = 131072;

/* test return values */

C(T_memcpy(SINK, SINK, B16) == SINK);
C(T_memcpy(SINK, SINK, B17) == SINK);

C(T_memmove(SINK, SINK, B16) == SINK);
C(T_memmove(SINK, SINK, B17) == SINK);

C(T_memmove(SINK + 16, SINK, B16) == SINK + 16);
C(T_memmove(SINK + 16, SINK, B17) == SINK + 16);

C(T_memmove(SINK, SINK + 16, B16) == SINK);
C(T_memmove(SINK, SINK + 16, B17) == SINK);

/* test memcpy and memmove when size is a non-zero multiple of 65536 */

fill_mem32(dst + screen_size - B16, B16, 0x78563412);
C(T_memcpy(dst + 32, dst + screen_size - B16, B16) == dst + 32);
C(T_memchr(dst, 0x00, 32) == dst);
C(T_memchr(dst, 0x12, 32) == NULL_ptr);
C(T_memchr(dst, 0x12, 33) == dst + 32);
C(T_memrchr(dst, 0x78, 32 + B16 + 32) == dst + 32 + B16 - 1);
const uint32_t pattern_1 = 0xA3A0A1A0;
const uint32_t pattern_2 = 0xFECDAB89;
fill_mem32(dst, 32, pattern_1);
fill_mem32(dst + 24576, B16, pattern_2);

C(T_memmove(dst + 61, dst, B16) == dst + 61);
C(T_memmem(dst, B17, &pattern_1, sizeof(pattern_1)) == dst);
C(T_memrmem(dst, B17, &pattern_1, sizeof(pattern_1)) == dst + 61 - 4 + 32);
C(T_memmove(dst + 24578, dst, B16) == dst + 24578);
C(T_memmem(dst, B16, &pattern_1, sizeof(pattern_1)) == dst + 0);
C(T_memrmem(dst, B16, &pattern_1, sizeof(pattern_1)) == dst + 24578 + 61 + 32 - 4);
C(T_memmem(dst, B16, &pattern_2, sizeof(pattern_2)) == dst + 24576 + 24578 + 61);
C(T_memrmem(dst, B16, &pattern_2, sizeof(pattern_2)) == dst + B16 - 4u - (((24578u - 24576u) - 61u) % 4u));

return 0;
}

int run_tests(void) {
int ret = 0;
/* boot_asprintf */
Expand Down Expand Up @@ -1027,6 +1079,9 @@ int run_tests(void) {
TEST(strrstr_test());
TEST(strchrnul_test());

TEST(mem65536_test());
os_ClrHome();

return 0;
}

Expand Down
6 changes: 4 additions & 2 deletions test/standalone/asprintf_fprintf/src/rename.s
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Expand Up @@ -2,7 +2,7 @@

.section .text

.global _T_memset, _T_memcpy, _T_memmove, _T_memcmp, _T_memccpy, _T_mempcpy, _T_memrchr, _T_memmem, _T_memrmem
.global _T_memset, _T_memcpy, _T_memmove, _T_memcmp, _T_memccpy, _T_mempcpy, _T_memchr, _T_memrchr, _T_memmem, _T_memrmem
.global _T_strlen, _T_strcmp, _T_strncmp, _T_stpcpy, _T_stpncpy, _T_strlcat, _T_strchrnul, _T_strrstr
.global _T_bzero

Expand All @@ -18,6 +18,8 @@ _T_memccpy:
jp _memccpy
_T_mempcpy:
jp _mempcpy
_T_memchr:
jp _memchr
_T_memrchr:
jp _memrchr
_T_memmem:
Expand Down Expand Up @@ -51,6 +53,6 @@ _T_bzero:
_NULL_ptr:
db $00, $00, $00

.extern _memset, _memcpy, _memmove, _memcmp, _memccpy, _mempcpy, _memrchr, _memmem, _memrmem
.extern _memset, _memcpy, _memmove, _memcmp, _memccpy, _mempcpy, _memchr, _memrchr, _memmem, _memrmem
.extern _strlen, _strcmp, _strncmp, _stpcpy, _stpncpy, _strlcat, _strchrnul, _strrstr
.extern _bzero
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