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# Copyright (c) 2021 Johannes Stoelp
.macro push reg
addi sp, sp, -8
sd \reg, 0(sp)
.endm
.macro pop reg
ld \reg, 0(sp)
addi sp, sp, 8
.endm
.section .text, "ax", @progbits
# extern "C" void yield(const void* new_stack, void** old_stack);
# ^^^^^^^^^ ^^^^^^^^^
# a0 (x10) a1 (x11)
.global yield
.type yield, @function
yield:
.cfi_startproc
# save return address
push ra
# push callee saved registers
push x8
push x9
push x18
push x19
push x20
push x21
push x22
push x23
push x24
push x25
push x26
push x27
# arg0: a0 holds new stack
# arg1: a1 holds addr to location current stack must be saved
sd sp, 0(a1) # save current stack ptr
mv sp, a0 # switch to new stack ptr
# pop callee saved registers
pop x27
pop x26
pop x25
pop x24
pop x23
pop x22
pop x21
pop x20
pop x19
pop x18
pop x9
pop x8
# restore return address
pop ra
ret
.cfi_endproc
.size yield, .-yield
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