-# Copyright 2022 Gabriel Jensen.

-# This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.

-# If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.

-

-.globl zap_memfor

-

-zap_memfor:

-# Address of the current element:

-#define addr %rbx

-# Address of the element after the last input element:

-#define afterbuf %r12

-# Size of each input element:

-#define sz %r13

-# Address of the function:

-#define fn %r14

-

- # We're gonna use callee-saved registers for storing values so they don't get overwritten with each function call.

-

- # Push the callee-saved registers:

- pushq addr

- pushq afterbuf

- pushq sz

- pushq fn

-

- # Move registers into place:

- movq %rdi,addr

- movq %rsi,sz

- movq %rdx,afterbuf

- movq %rcx,fn

-

- # Get the one-past-the-end address:

- imulq sz,afterbuf # afterbuf *= sz // Calculate the array size in bytes (sz * num). We're using signed multiply because the equivalent using the unsigned instruction would use more instructions.

- addq addr,afterbuf # afterbuf += addr

-

- # Iterate through the array:

-.loop:

-

- # Check if we have reached the one-past-the-end address:

- cmpq addr,afterbuf # if (addr == afterbuf)

- je .done # goto done

-

- # Call the provided function:

- movq addr,%rdi # // Provide the current address to the function.

- call *fn # fn(addr) // We don't need to save any registers for this as we only use callee-saved registers.

-

- # Continue to the next element:

- addq sz,addr # addr += sz

- jmp .loop # goto loop

-

- # Finish:

-.done:

-

- # Restore the callee-saved registers:

- popq fn

- popq sz

- popq afterbuf

- popq addr

-

- ret # return