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# 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
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