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# Copyright (c) 2020 Johannes Stoelp
.arch armv8-a
.section .text, "ax", @progbits
# extern "C" void yield(const void* new_stack, void** old_stack);
# ^^^^^^^^^ ^^^^^^^^^
# x0 x1
.global yield
.type yield, @function
yield:
.cfi_startproc
// prologue
stp x29, x30, [sp, -16]!
mov x29, sp
// push callee saved registers
stp x27, x28, [sp, -16]!
stp x25, x26, [sp, -16]!
stp x23, x24, [sp, -16]!
stp x21, x22, [sp, -16]!
stp x19, x20, [sp, -16]!
// arg0: x0 holds new stack
// arg1: x1 holds addr to location current stack must be saved
mov x2, sp
str x2, [x1] // save current stack ptr
mov sp, x0 // switch to new stack ptr
// pop callee saved registers
ldp x19, x20, [sp], 16
ldp x21, x22, [sp], 16
ldp x23, x24, [sp], 16
ldp x25, x26, [sp], 16
ldp x27, x28, [sp], 16
// epilogue
ldp x29, x30, [sp], 16
ret
.cfi_endproc
.size yield, .-yield
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