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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// System calls and other sys.stuff for ARM64, Darwin
// System calls are implemented in libSystem, this file contains
// trampolines that convert from Go to C calling convention.
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
TEXT notok<>(SB),NOSPLIT,$0
MOVD $0, R8
MOVD R8, (R8)
B 0(PC)
TEXT runtime·open_trampoline(SB),NOSPLIT,$0
SUB $16, RSP
MOVW 8(R0), R1 // arg 2 flags
MOVW 12(R0), R2 // arg 3 mode
MOVW R2, (RSP) // arg 3 is variadic, pass on stack
MOVD 0(R0), R0 // arg 1 pathname
BL libc_open(SB)
ADD $16, RSP
RET
TEXT runtime·close_trampoline(SB),NOSPLIT,$0
MOVW 0(R0), R0 // arg 1 fd
BL libc_close(SB)
RET
TEXT runtime·write_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 buf
MOVW 16(R0), R2 // arg 3 count
MOVW 0(R0), R0 // arg 1 fd
BL libc_write(SB)
MOVD $-1, R1
CMP R0, R1
BNE noerr
BL libc_error(SB)
MOVW (R0), R0
NEG R0, R0 // caller expects negative errno value
noerr:
RET
TEXT runtime·read_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 buf
MOVW 16(R0), R2 // arg 3 count
MOVW 0(R0), R0 // arg 1 fd
BL libc_read(SB)
MOVD $-1, R1
CMP R0, R1
BNE noerr
BL libc_error(SB)
MOVW (R0), R0
NEG R0, R0 // caller expects negative errno value
noerr:
RET
TEXT runtime·pipe_trampoline(SB),NOSPLIT,$0
BL libc_pipe(SB) // pointer already in R0
CMP $0, R0
BEQ 3(PC)
BL libc_error(SB) // return negative errno value
NEG R0, R0
RET
TEXT runtime·exit_trampoline(SB),NOSPLIT|NOFRAME,$0
MOVW 0(R0), R0
BL libc_exit(SB)
MOVD $1234, R0
MOVD $1002, R1
MOVD R0, (R1) // fail hard
TEXT runtime·raiseproc_trampoline(SB),NOSPLIT,$0
MOVD 0(R0), R19 // signal
BL libc_getpid(SB)
// arg 1 pid already in R0 from getpid
MOVD R19, R1 // arg 2 signal
BL libc_kill(SB)
RET
TEXT runtime·mmap_trampoline(SB),NOSPLIT,$0
MOVD R0, R19
MOVD 0(R19), R0 // arg 1 addr
MOVD 8(R19), R1 // arg 2 len
MOVW 16(R19), R2 // arg 3 prot
MOVW 20(R19), R3 // arg 4 flags
MOVW 24(R19), R4 // arg 5 fd
MOVW 28(R19), R5 // arg 6 off
BL libc_mmap(SB)
MOVD $0, R1
MOVD $-1, R2
CMP R0, R2
BNE ok
BL libc_error(SB)
MOVW (R0), R1
MOVD $0, R0
ok:
MOVD R0, 32(R19) // ret 1 p
MOVD R1, 40(R19) // ret 2 err
RET
TEXT runtime·munmap_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 len
MOVD 0(R0), R0 // arg 1 addr
BL libc_munmap(SB)
CMP $0, R0
BEQ 2(PC)
BL notok<>(SB)
RET
TEXT runtime·madvise_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 len
MOVW 16(R0), R2 // arg 3 advice
MOVD 0(R0), R0 // arg 1 addr
BL libc_madvise(SB)
RET
TEXT runtime·setitimer_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 new
MOVD 16(R0), R2 // arg 3 old
MOVW 0(R0), R0 // arg 1 which
BL libc_setitimer(SB)
RET
TEXT runtime·walltime_trampoline(SB),NOSPLIT,$0
// R0 already has *timeval
MOVD $0, R1 // no timezone needed
BL libc_gettimeofday(SB)
RET
GLOBL timebase<>(SB),NOPTR,$(machTimebaseInfo__size)
TEXT runtime·nanotime_trampoline(SB),NOSPLIT,$40
MOVD R0, R19
BL libc_mach_absolute_time(SB)
MOVD R0, 0(R19)
MOVW timebase<>+machTimebaseInfo_numer(SB), R20
MOVD $timebase<>+machTimebaseInfo_denom(SB), R21
LDARW (R21), R21 // atomic read
CMP $0, R21
BNE initialized
SUB $(machTimebaseInfo__size+15)/16*16, RSP
MOVD RSP, R0
BL libc_mach_timebase_info(SB)
MOVW machTimebaseInfo_numer(RSP), R20
MOVW machTimebaseInfo_denom(RSP), R21
ADD $(machTimebaseInfo__size+15)/16*16, RSP
MOVW R20, timebase<>+machTimebaseInfo_numer(SB)
MOVD $timebase<>+machTimebaseInfo_denom(SB), R22
STLRW R21, (R22) // atomic write
initialized:
MOVW R20, 8(R19)
MOVW R21, 12(R19)
RET
TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
MOVW sig+8(FP), R0
MOVD info+16(FP), R1
MOVD ctx+24(FP), R2
MOVD fn+0(FP), R11
BL (R11)
RET
TEXT runtime·sigtramp(SB),NOSPLIT,$192
// Save callee-save registers in the case of signal forwarding.
// Please refer to https://golang.org/issue/31827 .
MOVD R19, 8*4(RSP)
MOVD R20, 8*5(RSP)
MOVD R21, 8*6(RSP)
MOVD R22, 8*7(RSP)
MOVD R23, 8*8(RSP)
MOVD R24, 8*9(RSP)
MOVD R25, 8*10(RSP)
MOVD R26, 8*11(RSP)
MOVD R27, 8*12(RSP)
MOVD g, 8*13(RSP)
MOVD R29, 8*14(RSP)
FMOVD F8, 8*15(RSP)
FMOVD F9, 8*16(RSP)
FMOVD F10, 8*17(RSP)
FMOVD F11, 8*18(RSP)
FMOVD F12, 8*19(RSP)
FMOVD F13, 8*20(RSP)
FMOVD F14, 8*21(RSP)
FMOVD F15, 8*22(RSP)
// Save arguments.
MOVW R0, (8*1)(RSP) // sig
MOVD R1, (8*2)(RSP) // info
MOVD R2, (8*3)(RSP) // ctx
// this might be called in external code context,
// where g is not set.
BL runtime·load_g(SB)
#ifdef GOOS_ios
MOVD RSP, R6
CMP $0, g
BEQ nog
// iOS always use the main stack to run the signal handler.
// We need to switch to gsignal ourselves.
MOVD g_m(g), R11
MOVD m_gsignal(R11), R5
MOVD (g_stack+stack_hi)(R5), R6
nog:
// Restore arguments.
MOVW (8*1)(RSP), R0
MOVD (8*2)(RSP), R1
MOVD (8*3)(RSP), R2
// Reserve space for args and the stack pointer on the
// gsignal stack.
SUB $48, R6
// Save stack pointer.
MOVD RSP, R4
MOVD R4, (8*4)(R6)
// Switch to gsignal stack.
MOVD R6, RSP
// Save arguments.
MOVW R0, (8*1)(RSP)
MOVD R1, (8*2)(RSP)
MOVD R2, (8*3)(RSP)
#endif
// Call sigtrampgo.
MOVD $runtime·sigtrampgo(SB), R11
BL (R11)
#ifdef GOOS_ios
// Switch to old stack.
MOVD (8*4)(RSP), R5
MOVD R5, RSP
#endif
// Restore callee-save registers.
MOVD (8*4)(RSP), R19
MOVD (8*5)(RSP), R20
MOVD (8*6)(RSP), R21
MOVD (8*7)(RSP), R22
MOVD (8*8)(RSP), R23
MOVD (8*9)(RSP), R24
MOVD (8*10)(RSP), R25
MOVD (8*11)(RSP), R26
MOVD (8*12)(RSP), R27
MOVD (8*13)(RSP), g
MOVD (8*14)(RSP), R29
FMOVD (8*15)(RSP), F8
FMOVD (8*16)(RSP), F9
FMOVD (8*17)(RSP), F10
FMOVD (8*18)(RSP), F11
FMOVD (8*19)(RSP), F12
FMOVD (8*20)(RSP), F13
FMOVD (8*21)(RSP), F14
FMOVD (8*22)(RSP), F15
RET
TEXT runtime·cgoSigtramp(SB),NOSPLIT,$0
JMP runtime·sigtramp(SB)
TEXT runtime·sigprocmask_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 new
MOVD 16(R0), R2 // arg 3 old
MOVW 0(R0), R0 // arg 1 how
BL libc_pthread_sigmask(SB)
CMP $0, R0
BEQ 2(PC)
BL notok<>(SB)
RET
TEXT runtime·sigaction_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 new
MOVD 16(R0), R2 // arg 3 old
MOVW 0(R0), R0 // arg 1 how
BL libc_sigaction(SB)
CMP $0, R0
BEQ 2(PC)
BL notok<>(SB)
RET
TEXT runtime·usleep_trampoline(SB),NOSPLIT,$0
MOVW 0(R0), R0 // arg 1 usec
BL libc_usleep(SB)
RET
TEXT runtime·sysctl_trampoline(SB),NOSPLIT,$0
MOVW 8(R0), R1 // arg 2 miblen
MOVD 16(R0), R2 // arg 3 out
MOVD 24(R0), R3 // arg 4 size
MOVD 32(R0), R4 // arg 5 dst
MOVD 40(R0), R5 // arg 6 ndst
MOVD 0(R0), R0 // arg 1 mib
BL libc_sysctl(SB)
RET
TEXT runtime·kqueue_trampoline(SB),NOSPLIT,$0
BL libc_kqueue(SB)
RET
TEXT runtime·kevent_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 keventt
MOVW 16(R0), R2 // arg 3 nch
MOVD 24(R0), R3 // arg 4 ev
MOVW 32(R0), R4 // arg 5 nev
MOVD 40(R0), R5 // arg 6 ts
MOVW 0(R0), R0 // arg 1 kq
BL libc_kevent(SB)
MOVD $-1, R2
CMP R0, R2
BNE ok
BL libc_error(SB)
MOVW (R0), R0 // errno
NEG R0, R0 // caller wants it as a negative error code
ok:
RET
TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
SUB $16, RSP
MOVW 4(R0), R1 // arg 2 cmd
MOVW 8(R0), R2 // arg 3 arg
MOVW R2, (RSP) // arg 3 is variadic, pass on stack
MOVW 0(R0), R0 // arg 1 fd
BL libc_fcntl(SB)
ADD $16, RSP
RET
TEXT runtime·sigaltstack_trampoline(SB),NOSPLIT,$0
#ifdef GOOS_ios
// sigaltstack on iOS is not supported and will always
// run the signal handler on the main stack, so our sigtramp has
// to do the stack switch ourselves.
MOVW $43, R0
BL libc_exit(SB)
#else
MOVD 8(R0), R1 // arg 2 old
MOVD 0(R0), R0 // arg 1 new
CALL libc_sigaltstack(SB)
CBZ R0, 2(PC)
BL notok<>(SB)
#endif
RET
// Thread related functions
// mstart_stub is the first function executed on a new thread started by pthread_create.
// It just does some low-level setup and then calls mstart.
// Note: called with the C calling convention.
TEXT runtime·mstart_stub(SB),NOSPLIT,$160
// R0 points to the m.
// We are already on m's g0 stack.
// Save callee-save registers.
MOVD R19, 8(RSP)
MOVD R20, 16(RSP)
MOVD R21, 24(RSP)
MOVD R22, 32(RSP)
MOVD R23, 40(RSP)
MOVD R24, 48(RSP)
MOVD R25, 56(RSP)
MOVD R26, 64(RSP)
MOVD R27, 72(RSP)
MOVD g, 80(RSP)
MOVD R29, 88(RSP)
FMOVD F8, 96(RSP)
FMOVD F9, 104(RSP)
FMOVD F10, 112(RSP)
FMOVD F11, 120(RSP)
FMOVD F12, 128(RSP)
FMOVD F13, 136(RSP)
FMOVD F14, 144(RSP)
FMOVD F15, 152(RSP)
MOVD m_g0(R0), g
BL ·save_g(SB)
BL runtime·mstart(SB)
// Restore callee-save registers.
MOVD 8(RSP), R19
MOVD 16(RSP), R20
MOVD 24(RSP), R21
MOVD 32(RSP), R22
MOVD 40(RSP), R23
MOVD 48(RSP), R24
MOVD 56(RSP), R25
MOVD 64(RSP), R26
MOVD 72(RSP), R27
MOVD 80(RSP), g
MOVD 88(RSP), R29
FMOVD 96(RSP), F8
FMOVD 104(RSP), F9
FMOVD 112(RSP), F10
FMOVD 120(RSP), F11
FMOVD 128(RSP), F12
FMOVD 136(RSP), F13
FMOVD 144(RSP), F14
FMOVD 152(RSP), F15
// Go is all done with this OS thread.
// Tell pthread everything is ok (we never join with this thread, so
// the value here doesn't really matter).
MOVD $0, R0
RET
TEXT runtime·pthread_attr_init_trampoline(SB),NOSPLIT,$0
MOVD 0(R0), R0 // arg 1 attr
BL libc_pthread_attr_init(SB)
RET
TEXT runtime·pthread_attr_getstacksize_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 size
MOVD 0(R0), R0 // arg 1 attr
BL libc_pthread_attr_getstacksize(SB)
RET
TEXT runtime·pthread_attr_setdetachstate_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 state
MOVD 0(R0), R0 // arg 1 attr
BL libc_pthread_attr_setdetachstate(SB)
RET
TEXT runtime·pthread_create_trampoline(SB),NOSPLIT,$0
SUB $16, RSP
MOVD 0(R0), R1 // arg 2 state
MOVD 8(R0), R2 // arg 3 start
MOVD 16(R0), R3 // arg 4 arg
MOVD RSP, R0 // arg 1 &threadid (which we throw away)
BL libc_pthread_create(SB)
ADD $16, RSP
RET
TEXT runtime·raise_trampoline(SB),NOSPLIT,$0
MOVW 0(R0), R0 // arg 1 sig
BL libc_raise(SB)
RET
TEXT runtime·pthread_mutex_init_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 attr
MOVD 0(R0), R0 // arg 1 mutex
BL libc_pthread_mutex_init(SB)
RET
TEXT runtime·pthread_mutex_lock_trampoline(SB),NOSPLIT,$0
MOVD 0(R0), R0 // arg 1 mutex
BL libc_pthread_mutex_lock(SB)
RET
TEXT runtime·pthread_mutex_unlock_trampoline(SB),NOSPLIT,$0
MOVD 0(R0), R0 // arg 1 mutex
BL libc_pthread_mutex_unlock(SB)
RET
TEXT runtime·pthread_cond_init_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 attr
MOVD 0(R0), R0 // arg 1 cond
BL libc_pthread_cond_init(SB)
RET
TEXT runtime·pthread_cond_wait_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 mutex
MOVD 0(R0), R0 // arg 1 cond
BL libc_pthread_cond_wait(SB)
RET
TEXT runtime·pthread_cond_timedwait_relative_np_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 mutex
MOVD 16(R0), R2 // arg 3 timeout
MOVD 0(R0), R0 // arg 1 cond
BL libc_pthread_cond_timedwait_relative_np(SB)
RET
TEXT runtime·pthread_cond_signal_trampoline(SB),NOSPLIT,$0
MOVD 0(R0), R0 // arg 1 cond
BL libc_pthread_cond_signal(SB)
RET
TEXT runtime·pthread_self_trampoline(SB),NOSPLIT,$0
MOVD R0, R19 // R19 is callee-save
BL libc_pthread_self(SB)
MOVD R0, 0(R19) // return value
RET
TEXT runtime·pthread_kill_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 sig
MOVD 0(R0), R0 // arg 1 thread
BL libc_pthread_kill(SB)
RET
TEXT runtime·pthread_key_create_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 destructor
MOVD 0(R0), R0 // arg 1 *key
BL libc_pthread_key_create(SB)
RET
TEXT runtime·pthread_setspecific_trampoline(SB),NOSPLIT,$0
MOVD 8(R0), R1 // arg 2 value
MOVD 0(R0), R0 // arg 1 key
BL libc_pthread_setspecific(SB)
RET
// syscall calls a function in libc on behalf of the syscall package.
// syscall takes a pointer to a struct like:
// struct {
// fn uintptr
// a1 uintptr
// a2 uintptr
// a3 uintptr
// r1 uintptr
// r2 uintptr
// err uintptr
// }
// syscall must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscall(SB),NOSPLIT,$0
SUB $16, RSP // push structure pointer
MOVD R0, 8(RSP)
MOVD 0(R0), R12 // fn
MOVD 16(R0), R1 // a2
MOVD 24(R0), R2 // a3
MOVD 8(R0), R0 // a1
// If fn is declared as vararg, we have to pass the vararg arguments on the stack.
// (Because ios decided not to adhere to the standard arm64 calling convention, sigh...)
// The only libSystem calls we support that are vararg are open, fcntl, and ioctl,
// which are all of the form fn(x, y, ...). So we just need to put the 3rd arg
// on the stack as well.
// If we ever have other vararg libSystem calls, we might need to handle more cases.
MOVD R2, (RSP)
BL (R12)
MOVD 8(RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 32(R2) // save r1
MOVD R1, 40(R2) // save r2
CMPW $-1, R0
BNE ok
SUB $16, RSP // push structure pointer
MOVD R2, 8(RSP)
BL libc_error(SB)
MOVW (R0), R0
MOVD 8(RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 48(R2) // save err
ok:
RET
// syscallX calls a function in libc on behalf of the syscall package.
// syscallX takes a pointer to a struct like:
// struct {
// fn uintptr
// a1 uintptr
// a2 uintptr
// a3 uintptr
// r1 uintptr
// r2 uintptr
// err uintptr
// }
// syscallX must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscallX(SB),NOSPLIT,$0
SUB $16, RSP // push structure pointer
MOVD R0, (RSP)
MOVD 0(R0), R12 // fn
MOVD 16(R0), R1 // a2
MOVD 24(R0), R2 // a3
MOVD 8(R0), R0 // a1
BL (R12)
MOVD (RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 32(R2) // save r1
MOVD R1, 40(R2) // save r2
CMP $-1, R0
BNE ok
SUB $16, RSP // push structure pointer
MOVD R2, (RSP)
BL libc_error(SB)
MOVW (R0), R0
MOVD (RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 48(R2) // save err
ok:
RET
// syscallPtr is like syscallX except that the libc function reports an
// error by returning NULL and setting errno.
TEXT runtime·syscallPtr(SB),NOSPLIT,$0
SUB $16, RSP // push structure pointer
MOVD R0, (RSP)
MOVD 0(R0), R12 // fn
MOVD 16(R0), R1 // a2
MOVD 24(R0), R2 // a3
MOVD 8(R0), R0 // a1
BL (R12)
MOVD (RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 32(R2) // save r1
MOVD R1, 40(R2) // save r2
CMP $0, R0
BNE ok
SUB $16, RSP // push structure pointer
MOVD R2, (RSP)
BL libc_error(SB)
MOVW (R0), R0
MOVD (RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 48(R2) // save err
ok:
RET
// syscall6 calls a function in libc on behalf of the syscall package.
// syscall6 takes a pointer to a struct like:
// struct {
// fn uintptr
// a1 uintptr
// a2 uintptr
// a3 uintptr
// a4 uintptr
// a5 uintptr
// a6 uintptr
// r1 uintptr
// r2 uintptr
// err uintptr
// }
// syscall6 must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscall6(SB),NOSPLIT,$0
SUB $16, RSP // push structure pointer
MOVD R0, 8(RSP)
MOVD 0(R0), R12 // fn
MOVD 16(R0), R1 // a2
MOVD 24(R0), R2 // a3
MOVD 32(R0), R3 // a4
MOVD 40(R0), R4 // a5
MOVD 48(R0), R5 // a6
MOVD 8(R0), R0 // a1
// If fn is declared as vararg, we have to pass the vararg arguments on the stack.
// See syscall above. The only function this applies to is openat, for which the 4th
// arg must be on the stack.
MOVD R3, (RSP)
BL (R12)
MOVD 8(RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 56(R2) // save r1
MOVD R1, 64(R2) // save r2
CMPW $-1, R0
BNE ok
SUB $16, RSP // push structure pointer
MOVD R2, 8(RSP)
BL libc_error(SB)
MOVW (R0), R0
MOVD 8(RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 72(R2) // save err
ok:
RET
// syscall6X calls a function in libc on behalf of the syscall package.
// syscall6X takes a pointer to a struct like:
// struct {
// fn uintptr
// a1 uintptr
// a2 uintptr
// a3 uintptr
// a4 uintptr
// a5 uintptr
// a6 uintptr
// r1 uintptr
// r2 uintptr
// err uintptr
// }
// syscall6X must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscall6X(SB),NOSPLIT,$0
SUB $16, RSP // push structure pointer
MOVD R0, (RSP)
MOVD 0(R0), R12 // fn
MOVD 16(R0), R1 // a2
MOVD 24(R0), R2 // a3
MOVD 32(R0), R3 // a4
MOVD 40(R0), R4 // a5
MOVD 48(R0), R5 // a6
MOVD 8(R0), R0 // a1
BL (R12)
MOVD (RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 56(R2) // save r1
MOVD R1, 64(R2) // save r2
CMP $-1, R0
BNE ok
SUB $16, RSP // push structure pointer
MOVD R2, (RSP)
BL libc_error(SB)
MOVW (R0), R0
MOVD (RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 72(R2) // save err
ok:
RET
// syscallNoErr is like syscall6 but does not check for errors, and
// only returns one value, for use with standard C ABI library functions.
TEXT runtime·syscallNoErr(SB),NOSPLIT,$0
SUB $16, RSP // push structure pointer
MOVD R0, (RSP)
MOVD 0(R0), R12 // fn
MOVD 16(R0), R1 // a2
MOVD 24(R0), R2 // a3
MOVD 32(R0), R3 // a4
MOVD 40(R0), R4 // a5
MOVD 48(R0), R5 // a6
MOVD 8(R0), R0 // a1
BL (R12)
MOVD (RSP), R2 // pop structure pointer
ADD $16, RSP
MOVD R0, 56(R2) // save r1
RET