src/runtime/asm_wasm.s

// Copyright 2018 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.

#include "go_asm.h"
#include "go_tls.h"
#include "funcdata.h"
#include "textflag.h"

TEXT runtime·rt0_go(SB), NOSPLIT, $0
	// save m->g0 = g0
	MOVD $runtime·g0(SB), runtime·m0+m_g0(SB)
	// save m0 to g0->m
	MOVD $runtime·m0(SB), runtime·g0+g_m(SB)
	// set g to g0
	MOVD $runtime·g0(SB), g
	CALLNORESUME runtime·check(SB)
	CALLNORESUME runtime·args(SB)
	CALLNORESUME runtime·osinit(SB)
	CALLNORESUME runtime·schedinit(SB)
	MOVD $0, 0(SP)
	MOVD $runtime·mainPC(SB), 8(SP)
	CALLNORESUME runtime·newproc(SB)
	CALL runtime·mstart(SB) // WebAssembly stack will unwind when switching to another goroutine
	UNDEF

DATA  runtime·mainPC+0(SB)/8,$runtime·main(SB)
GLOBL runtime·mainPC(SB),RODATA,$8

// func checkASM() bool
TEXT ·checkASM(SB), NOSPLIT, $0-1
	MOVB $1, ret+0(FP)
	RET

TEXT runtime·gogo(SB), NOSPLIT, $0-8
	MOVD buf+0(FP), R0
	MOVD gobuf_g(R0), g
	MOVD gobuf_sp(R0), SP

	I64Load gobuf_pc(R0)
	I32WrapI64
	I32Const $16
	I32ShrU
	Set PC_F

	I64Load gobuf_pc(R0)
	I64Const $0xFFFF
	I64And
	I32WrapI64
	Set PC_B

	MOVD gobuf_ret(R0), RET0
	MOVD gobuf_ctxt(R0), CTXT
	// clear to help garbage collector
	MOVD $0, gobuf_sp(R0)
	MOVD $0, gobuf_ret(R0)
	MOVD $0, gobuf_ctxt(R0)

	I32Const $1
	Return

// func mcall(fn func(*g))
// Switch to m->g0's stack, call fn(g).
// Fn must never return. It should gogo(&g->sched)
// to keep running g.
TEXT runtime·mcall(SB), NOSPLIT, $0-8
	// CTXT = fn
	MOVD fn+0(FP), CTXT
	// R1 = g.m
	MOVD g_m(g), R1
	// R2 = g0
	MOVD m_g0(R1), R2

	// save state in g->sched
	MOVD 0(SP), g_sched+gobuf_pc(g)     // caller's PC
	MOVD $fn+0(FP), g_sched+gobuf_sp(g) // caller's SP
	MOVD g, g_sched+gobuf_g(g)

	// if g == g0 call badmcall
	Get g
	Get R2
	I64Eq
	If
		JMP runtime·badmcall(SB)
	End

	// switch to g0's stack
	I64Load (g_sched+gobuf_sp)(R2)
	I64Const $8
	I64Sub
	I32WrapI64
	Set SP

	// set arg to current g
	MOVD g, 0(SP)

	// switch to g0
	MOVD R2, g

	// call fn
	Get CTXT
	I32WrapI64
	I64Load $0
	CALL

	Get SP
	I32Const $8
	I32Add
	Set SP

	JMP runtime·badmcall2(SB)

// func systemstack(fn func())
TEXT runtime·systemstack(SB), NOSPLIT, $0-8
	// R0 = fn
	MOVD fn+0(FP), R0
	// R1 = g.m
	MOVD g_m(g), R1
	// R2 = g0
	MOVD m_g0(R1), R2

	// if g == g0
	Get g
	Get R2
	I64Eq
	If
		// no switch:
		MOVD R0, CTXT

		Get CTXT
		I32WrapI64
		I64Load $0
		JMP
	End

	// if g != m.curg
	Get g
	I64Load m_curg(R1)
	I64Ne
	If
		CALLNORESUME runtime·badsystemstack(SB)
	End

	// switch:

	// save state in g->sched. Pretend to
	// be systemstack_switch if the G stack is scanned.
	MOVD $runtime·systemstack_switch(SB), g_sched+gobuf_pc(g)

	MOVD SP, g_sched+gobuf_sp(g)
	MOVD g, g_sched+gobuf_g(g)

	// switch to g0
	MOVD R2, g

	// make it look like mstart called systemstack on g0, to stop traceback
	I64Load (g_sched+gobuf_sp)(R2)
	I64Const $8
	I64Sub
	Set R3

	MOVD $runtime·mstart(SB), 0(R3)
	MOVD R3, SP

	// call fn
	MOVD R0, CTXT

	Get CTXT
	I32WrapI64
	I64Load $0
	CALL

	// switch back to g
	MOVD g_m(g), R1
	MOVD m_curg(R1), R2
	MOVD R2, g
	MOVD g_sched+gobuf_sp(R2), SP
	MOVD $0, g_sched+gobuf_sp(R2)
	RET

TEXT runtime·systemstack_switch(SB), NOSPLIT, $0-0
	RET

TEXT runtime·return0(SB), NOSPLIT, $0-0
	MOVD $0, RET0
	RET

TEXT runtime·jmpdefer(SB), NOSPLIT, $0-16
	MOVD fv+0(FP), CTXT

	Get CTXT
	I64Eqz
	If
		CALLNORESUME runtime·sigpanic(SB)
	End

	// caller sp after CALL
	I64Load argp+8(FP)
	I64Const $8
	I64Sub
	I32WrapI64
	Set SP

	// decrease PC_B by 1 to CALL again
	Get SP
	I32Load16U (SP)
	I32Const $1
	I32Sub
	I32Store16 $0

	// but first run the deferred function
	Get CTXT
	I32WrapI64
	I64Load $0
	JMP

TEXT runtime·asminit(SB), NOSPLIT, $0-0
	// No per-thread init.
	RET

TEXT ·publicationBarrier(SB), NOSPLIT, $0-0
	RET

TEXT runtime·procyield(SB), NOSPLIT, $0-0 // FIXME
	RET

TEXT runtime·breakpoint(SB), NOSPLIT, $0-0
	UNDEF

// Called during function prolog when more stack is needed.
//
// The traceback routines see morestack on a g0 as being
// the top of a stack (for example, morestack calling newstack
// calling the scheduler calling newm calling gc), so we must
// record an argument size. For that purpose, it has no arguments.
TEXT runtime·morestack(SB), NOSPLIT, $0-0
	// R1 = g.m
	MOVD g_m(g), R1

	// R2 = g0
	MOVD m_g0(R1), R2

	// Cannot grow scheduler stack (m->g0).
	Get g
	Get R1
	I64Eq
	If
		CALLNORESUME runtime·badmorestackg0(SB)
	End

	// Cannot grow signal stack (m->gsignal).
	Get g
	I64Load m_gsignal(R1)
	I64Eq
	If
		CALLNORESUME runtime·badmorestackgsignal(SB)
	End

	// Called from f.
	// Set m->morebuf to f's caller.
	MOVD 8(SP), m_morebuf+gobuf_pc(R1)
	MOVD $16(SP), m_morebuf+gobuf_sp(R1) // f's caller's SP
	MOVD g, m_morebuf+gobuf_g(R1)

	// Set g->sched to context in f.
	MOVD 0(SP), g_sched+gobuf_pc(g)
	MOVD g, g_sched+gobuf_g(g)
	MOVD $8(SP), g_sched+gobuf_sp(g) // f's SP
	MOVD CTXT, g_sched+gobuf_ctxt(g)

	// Call newstack on m->g0's stack.
	MOVD R2, g
	MOVD g_sched+gobuf_sp(R2), SP
	CALL runtime·newstack(SB)
	UNDEF // crash if newstack returns

// morestack but not preserving ctxt.
TEXT runtime·morestack_noctxt(SB),NOSPLIT,$0
	MOVD $0, CTXT
	JMP runtime·morestack(SB)

TEXT ·asmcgocall(SB), NOSPLIT, $0-0
	UNDEF

TEXT ·cgocallback_gofunc(SB), NOSPLIT, $16-32
	UNDEF

#define DISPATCH(NAME, MAXSIZE) \
	Get R0; \
	I64Const $MAXSIZE; \
	I64LeU; \
	If; \
		JMP NAME(SB); \
	End

TEXT reflect·call(SB), NOSPLIT, $0-0
	JMP ·reflectcall(SB)

TEXT ·reflectcall(SB), NOSPLIT, $0-32
	I64Load fn+8(FP)
	I64Eqz
	If
		CALLNORESUME runtime·sigpanic(SB)
	End

	MOVW argsize+24(FP), R0

	DISPATCH(runtime·call32, 32)
	DISPATCH(runtime·call64, 64)
	DISPATCH(runtime·call128, 128)
	DISPATCH(runtime·call256, 256)
	DISPATCH(runtime·call512, 512)
	DISPATCH(runtime·call1024, 1024)
	DISPATCH(runtime·call2048, 2048)
	DISPATCH(runtime·call4096, 4096)
	DISPATCH(runtime·call8192, 8192)
	DISPATCH(runtime·call16384, 16384)
	DISPATCH(runtime·call32768, 32768)
	DISPATCH(runtime·call65536, 65536)
	DISPATCH(runtime·call131072, 131072)
	DISPATCH(runtime·call262144, 262144)
	DISPATCH(runtime·call524288, 524288)
	DISPATCH(runtime·call1048576, 1048576)
	DISPATCH(runtime·call2097152, 2097152)
	DISPATCH(runtime·call4194304, 4194304)
	DISPATCH(runtime·call8388608, 8388608)
	DISPATCH(runtime·call16777216, 16777216)
	DISPATCH(runtime·call33554432, 33554432)
	DISPATCH(runtime·call67108864, 67108864)
	DISPATCH(runtime·call134217728, 134217728)
	DISPATCH(runtime·call268435456, 268435456)
	DISPATCH(runtime·call536870912, 536870912)
	DISPATCH(runtime·call1073741824, 1073741824)
	JMP runtime·badreflectcall(SB)

#define CALLFN(NAME, MAXSIZE) \
TEXT NAME(SB), WRAPPER, $MAXSIZE-32; \
	NO_LOCAL_POINTERS; \
	MOVW argsize+24(FP), R0; \
	\
	Get R0; \
	I64Eqz; \
	Not; \
	If; \
		Get SP; \
		I64Load argptr+16(FP); \
		I32WrapI64; \
		I64Load argsize+24(FP); \
		I64Const $3; \
		I64ShrU; \
		I32WrapI64; \
		Call runtime·wasmMove(SB); \
	End; \
	\
	MOVD f+8(FP), CTXT; \
	Get CTXT; \
	I32WrapI64; \
	I64Load $0; \
	CALL; \
	\
	I64Load32U retoffset+28(FP); \
	Set R0; \
	\
	MOVD argtype+0(FP), RET0; \
	\
	I64Load argptr+16(FP); \
	Get R0; \
	I64Add; \
	Set RET1; \
	\
	Get SP; \
	I64ExtendUI32; \
	Get R0; \
	I64Add; \
	Set RET2; \
	\
	I64Load32U argsize+24(FP); \
	Get R0; \
	I64Sub; \
	Set RET3; \
	\
	CALL callRet<>(SB); \
	RET

// callRet copies return values back at the end of call*. This is a
// separate function so it can allocate stack space for the arguments
// to reflectcallmove. It does not follow the Go ABI; it expects its
// arguments in registers.
TEXT callRet<>(SB), NOSPLIT, $32-0
	NO_LOCAL_POINTERS
	MOVD RET0, 0(SP)
	MOVD RET1, 8(SP)
	MOVD RET2, 16(SP)
	MOVD RET3, 24(SP)
	CALL runtime·reflectcallmove(SB)
	RET

CALLFN(·call32, 32)
CALLFN(·call64, 64)
CALLFN(·call128, 128)
CALLFN(·call256, 256)
CALLFN(·call512, 512)
CALLFN(·call1024, 1024)
CALLFN(·call2048, 2048)
CALLFN(·call4096, 4096)
CALLFN(·call8192, 8192)
CALLFN(·call16384, 16384)
CALLFN(·call32768, 32768)
CALLFN(·call65536, 65536)
CALLFN(·call131072, 131072)
CALLFN(·call262144, 262144)
CALLFN(·call524288, 524288)
CALLFN(·call1048576, 1048576)
CALLFN(·call2097152, 2097152)
CALLFN(·call4194304, 4194304)
CALLFN(·call8388608, 8388608)
CALLFN(·call16777216, 16777216)
CALLFN(·call33554432, 33554432)
CALLFN(·call67108864, 67108864)
CALLFN(·call134217728, 134217728)
CALLFN(·call268435456, 268435456)
CALLFN(·call536870912, 536870912)
CALLFN(·call1073741824, 1073741824)

TEXT runtime·goexit(SB), NOSPLIT, $0-0
	NOP // first PC of goexit is skipped
	CALL runtime·goexit1(SB) // does not return
	UNDEF

TEXT runtime·cgocallback(SB), NOSPLIT, $32-32
	UNDEF

// gcWriteBarrier performs a heap pointer write and informs the GC.
//
// gcWriteBarrier does NOT follow the Go ABI. It has two WebAssembly parameters:
// R0: the destination of the write (i64)
// R1: the value being written (i64)
TEXT runtime·gcWriteBarrier(SB), NOSPLIT, $16
	// R3 = g.m
	MOVD g_m(g), R3
	// R4 = p
	MOVD m_p(R3), R4
	// R5 = wbBuf.next
	MOVD p_wbBuf+wbBuf_next(R4), R5

	// Record value
	MOVD R1, 0(R5)
	// Record *slot
	MOVD R0, 8(R5)

	// Increment wbBuf.next
	Get R5
	I64Const $16
	I64Add
	Set R5
	MOVD R5, p_wbBuf+wbBuf_next(R4)

	Get R5
	I64Load (p_wbBuf+wbBuf_end)(R4)
	I64Eq
	If
		// Flush
		MOVD R0, 0(SP)
		MOVD R1, 8(SP)
		CALLNORESUME runtime·wbBufFlush(SB)
	End

	// Do the write
	MOVD R1, (R0)

	RET