Initial commit

common/ndsabi/rmemcpy.s

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+// SPDX-License-Identifier: Zlib
+// SPDX-FileNotice: Modified from the original version by the BlocksDS project.
+//
+// Copyright (C) 2021-2023 agbabi contributors
+//
+// Support:
+//    __ndsabi_rmemcpy, __ndsabi_rmemcpy1
+
+#include <nds/asminc.h>
+
+#include "macros.inc"
+
+    .syntax unified
+
+    .arm
+
+
+BEGIN_ASM_FUNC __ndsabi_rmemcpy
+
+    @ >6-bytes is roughly the threshold when byte-by-byte copy is slower
+    cmp     r2, #6
+    ble     __ndsabi_rmemcpy1
+
+    align_switch r0, r1, r3, __ndsabi_rmemcpy1, .Lcopy_halves
+
+    @ Check if end needs word aligning
+    add     r3, r0, r2
+    joaobapt_test r3
+
+    @ Copy byte tail to align
+    submi   r2, r2, #1
+    ldrbmi  r3, [r1, r2]
+    strbmi  r3, [r0, r2]
+    @ r2 is now half aligned
+
+    @ Copy half tail to align
+    subcs   r2, r2, #2
+    ldrhcs  r3, [r1, r2]
+    strhcs  r3, [r0, r2]
+    @ r2 is now word aligned
+
+    cmp     r2, #32
+    blt     .Lcopy_words
+
+    @ Word aligned, 32-byte copy
+    push    {r0-r1, r4-r10}
+    add     r0, r0, r2
+    add     r1, r1, r2
+.Lloop_32:
+    subs    r2, r2, #32
+    ldmdbge r1!, {r3-r10}
+    stmdbge r0!, {r3-r10}
+    bgt     .Lloop_32
+    pop     {r0-r1, r4-r10}
+    bxeq    lr
+
+    @ < 32 bytes remaining to be copied
+    add     r2, r2, #32
+
+.Lcopy_words:
+    subs    r2, r2, #4
+    ldrge   r3, [r1, r2]
+    strge   r3, [r0, r2]
+    bgt     .Lcopy_words
+    bxeq    lr
+
+    @ Copy byte & half head
+    joaobapt_test_into r3, r2
+    @ Copy half
+    addcs   r2, r2, #2
+    ldrhcs  r3, [r1, r2]
+    strhcs  r3, [r0, r2]
+    @ Copy byte
+    ldrbmi  r3, [r1]
+    strbmi  r3, [r0]
+    bx      lr
+
+.Lcopy_halves:
+    @ Copy byte tail to align
+    add     r3, r0, r2
+    tst     r3, #1
+    subne   r2, r2, #1
+    ldrbne  r3, [r1, r2]
+    strbne  r3, [r0, r2]
+    @ r2 is now half aligned
+
+.Lloop_2:
+    subs    r2, r2, #2
+    ldrhge  r3, [r1, r2]
+    strhge  r3, [r0, r2]
+    bgt     .Lloop_2
+    bxeq    lr
+
+    @ Copy byte head
+    ldrb    r3, [r1]
+    strb    r3, [r0]
+    bx      lr
+
+
+BEGIN_ASM_FUNC_NO_SECTION __ndsabi_rmemcpy1
+
+    subs    r2, r2, #1
+    ldrbge  r3, [r1, r2]
+    strbge  r3, [r0, r2]
+    bgt     __ndsabi_rmemcpy1
+    bx      lr