Use CRT implementation of memset/memcpy (#67788)

* Use CRT implementation of memset/memcpy

* Remove the outdated comment:

Author: kunalspathak

src/coreclr/vm/amd64/CrtHelpers.asm

@@ -6,11 +6,6 @@
 
 ;
 ; ==--==
-; ***********************************************************************
-; File: CrtHelpers.asm, see history in asmhelpers.asm
-;
-; ***********************************************************************
-
 include AsmMacros.inc
 
 extern memset:proc

src/coreclr/vm/arm64/crthelpers.asm

@@ -1,176 +1,86 @@
 ; Licensed to the .NET Foundation under one or more agreements.
 ; The .NET Foundation licenses this file to you under the MIT license.
 
-;; ==++==
-;;
-
-;;
-;; ==--==
+; ==++==
+;
 
+;
+; ==--==
 #include "ksarm64.h"
+#include "asmconstants.h"
+#include "asmmacros.h"
 
-    TEXTAREA
+    IMPORT memset
+    IMPORT memmove
 
-;void JIT_MemSet(void *dst, int val, SIZE_T count)
-;{
-;    uint64_t valEx = (unsigned char)val;
-;    valEx = valEx | valEx << 8;
-;    valEx = valEx | valEx << 16;
-;    valEx = valEx | valEx << 32;
-;
-;    count-=16;
-;
-;    while(count >= 0)
-;    {
-;        *(uint64_t*)dst = valEx;
-;        dst = (uint64_t*)dst + 1;
-;        *(uint64_t*)dst = valEx;
-;        dst = (uint64_t*)dst + 1;
-;        count-=16;
-;    }
-;
-;    if(count & 8)
-;    {
-;        *(uint64_t*)dst = valEx;
-;        dst = (uint64_t*)dst + 1;
-;    }
-;
-;    if(count & 4)
-;    {
-;        *(uint32_t*)dst = (uint32_t)valEx;
-;        dst = (uint32_t*)dst + 1;
-;    }
-;
-;    if(count & 2)
-;    {
-;        *(uint16_t*)dst = (uint16_t)valEx;
-;        dst = (uint16_t*)dst + 1;
-;    }
-;
-;    if(count & 1)
-;    {
-;        *(uint8_t*)dst = (uint8_t)valEx;
-;    }
-;}
+; JIT_MemSet/JIT_MemCpy
+;
+; It is IMPORTANT that the exception handling code is able to find these guys
+; on the stack, but on windows platforms we can just defer to the platform
+; implementation.
 ;
 
-; Assembly code corresponding to above C++ method. JIT_MemSet can AV and clr exception personality routine needs to
-; determine if the exception has taken place inside JIT_Memset in order to throw corresponding managed exception.
-; Determining this is slow if the method were implemented as C++ method (using unwind info). In .asm file by adding JIT_MemSet_End
-; marker it can be easily determined if exception happened in JIT_MemSet. Therefore, JIT_MemSet has been written in assembly instead of
-; as C++ method.
+; void JIT_MemSet(void* dest, int c, size_t count)
+;
+; Purpose:
+;    Sets the first "count" bytes of the block of memory pointed byte
+;    "dest" to the specified value (interpreted as an unsigned char).
+;
+; Entry:
+;    RCX: void* dest    - Pointer to the block of memory to fill.
+;    RDX: int c         - Value to be set.
+;    R8:  size_t count  - Number of bytes to be set to the value.
+;
+; Exit:
+;
+; Uses:
+;
+; Exceptions:
+;
 
+    TEXTAREA
+    
     LEAF_ENTRY JIT_MemSet
-    ands        w1, w1, #0xff
-    orr         w1, w1, w1, lsl #8
-    orr         w1, w1, w1, lsl #0x10
-    orr         x1, x1, x1, lsl #0x20
+        cbz x2, JIT_MemSet_ret  ; check if count is zero, no bytes to set
 
-    b           JIT_MemSet_bottom
-JIT_MemSet_top
-    stp         x1, x1, [x0], #16
-JIT_MemSet_bottom
-    subs        x2, x2, #16
-    bge        JIT_MemSet_top
-
-    tbz         x2, #3, JIT_MemSet_tbz4
-    str         x1, [x0], #8
-JIT_MemSet_tbz4
-    tbz         x2, #2, JIT_MemSet_tbz2
-    str         w1, [x0], #4
-JIT_MemSet_tbz2
-    tbz         x2, #1, JIT_MemSet_tbz1
-    strh        w1, [x0], #2
-JIT_MemSet_tbz1
-    tbz         x2, #0, JIT_MemSet_ret
-    strb        w1, [x0]
-JIT_MemSet_ret
-    ret         lr
-    LEAF_END
-
-    LEAF_ENTRY JIT_MemSet_End
-    nop
-    LEAF_END
+        ldrb wzr, [x0]          ; check dest for null
 
+        b     memset            ; forward to the CRT implementation
 
-; See comments above for JIT_MemSet
+JIT_MemSet_ret
+        ret         lr
+    
+    LEAF_END_MARKED JIT_MemSet
 
-;void JIT_MemCpy(void *dst, const void *src, SIZE_T count)
-;{
-;    count-=16;
-;
-;    while(count >= 0)
-;    {
-;        *(unit64_t*)dst = *(unit64_t*)src;
-;        dst = (unit64_t*)dst + 1;
-;        src = (unit64_t*)src + 1;
-;        *(unit64_t*)dst = *(unit64_t*)src;
-;        dst = (unit64_t*)dst + 1;
-;        src = (unit64_t*)src + 1;
-;        count-=16;
-;    }
-;
-;    if(count & 8)
-;    {
-;        *(unit64_t*)dst = *(unit64_t*)src;
-;        dst = (unit64_t*)dst + 1;
-;        src = (unit64_t*)src + 1;
-;    }
-;
-;    if(count & 4)
-;    {
-;        *(unit32_t*)dst = *(unit32_t*)src;
-;        dst = (unit32_t*)dst + 1;
-;        src = (unit32_t*)src + 1;
-;    }
-;
-;    if(count & 2)
-;    {
-;        *(unit16_t*)dst = *(unit16_t*)src;
-;        dst = (unit16_t*)dst + 1;
-;        src = (unit16_t*)src + 1;
-;    }
-;
-;    if(count & 1)
-;    {
-;        *(unit8_t*)dst = *(unit8_t*)src;
-;    }
-;}
+; void JIT_MemCpy(void* dest, const void* src, size_t count)
+;
+; Purpose:
+;    Copies the values of "count" bytes from the location pointed to
+;    by "src" to the memory block pointed by "dest".
+;
+; Entry:
+;    RCX: void* dest             - Pointer to the destination array where content is to be copied.
+;    RDX: const void* src        - Pointer to the source of the data to be copied.
+;    R8:  size_t count           - Number of bytes to copy.
+;
+; Exit:
+;
+; Uses:
+;
+; Exceptions:
 ;
-
-; Assembly code corresponding to above C++ method.
-; See comments above for JIT_MemSet method
     LEAF_ENTRY JIT_MemCpy
-    b           JIT_MemCpy_bottom
-JIT_MemCpy_top
-    ldp         x8, x9, [x1], #16
-    stp         x8, x9, [x0], #16
-JIT_MemCpy_bottom
-    subs        x2, x2, #16
-    bge         JIT_MemCpy_top
+        cbz x2, JIT_MemCpy_ret  ; check if count is zero, no bytes to set
+
+        ldrb wzr, [x0]          ; check dest for null
+        ldrb wzr, [x1]          ; check src for null
+
+        b     memmove           ; forward to the CRT implementation
 
-    tbz         x2, #3, JIT_MemCpy_tbz4
-    ldr         x8, [x1], #8
-    str         x8, [x0], #8
-JIT_MemCpy_tbz4
-    tbz         x2, #2, JIT_MemCpy_tbz2
-    ldr         w8, [x1], #4
-    str         w8, [x0], #4
-JIT_MemCpy_tbz2
-    tbz         x2, #1, JIT_MemCpy_tbz1
-    ldrsh       w8, [x1], #2
-    strh        w8, [x0], #2
-JIT_MemCpy_tbz1
-    tbz         x2, #0, JIT_MemCpy_ret
-    ldrsb       w8, [x1]
-    strb        w8, [x0]
 JIT_MemCpy_ret
     ret         lr
-    LEAF_END
 
-    LEAF_ENTRY JIT_MemCpy_End
-    nop
-    LEAF_END
+    LEAF_END_MARKED JIT_MemCpy
 
 ; Must be at very end of file
-    END
+    END