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// 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 "textflag.h"
// _rt0_wasm_js is not used itself. It only exists to mark the exported functions as alive.
TEXT _rt0_wasm_js(SB),NOSPLIT,$0
I32Const $wasm_export_run(SB)
Drop
I32Const $wasm_export_resume(SB)
Drop
I32Const $wasm_export_getsp(SB)
Drop
// wasm_export_run gets called from JavaScript. It initializes the Go runtime and executes Go code until it needs
// to wait for an event. It does NOT follow the Go ABI. It has two WebAssembly parameters:
// R0: argc (i32)
// R1: argv (i32)
TEXT wasm_export_run(SB),NOSPLIT,$0
MOVD $runtime·wasmStack+(m0Stack__size-16)(SB), SP
Get SP
Get R0 // argc
I64ExtendI32U
I64Store $0
Get SP
Get R1 // argv
I64ExtendI32U
I64Store $8
I32Const $0 // entry PC_B
Call runtime·rt0_go(SB)
Drop
Call wasm_pc_f_loop(SB)
Return
// wasm_export_resume gets called from JavaScript. It resumes the execution of Go code until it needs to wait for
// an event.
TEXT wasm_export_resume(SB),NOSPLIT,$0
I32Const $0
Call runtime·handleEvent(SB)
Drop
Call wasm_pc_f_loop(SB)
Return
TEXT wasm_pc_f_loop(SB),NOSPLIT,$0
// Call the function for the current PC_F. Repeat until PAUSE != 0 indicates pause or exit.
// The WebAssembly stack may unwind, e.g. when switching goroutines.
// The Go stack on the linear memory is then used to jump to the correct functions
// with this loop, without having to restore the full WebAssembly stack.
// It is expected to have a pending call before entering the loop, so check PAUSE first.
Get PAUSE
I32Eqz
If
loop:
Loop
// Get PC_B & PC_F from -8(SP)
Get SP
I32Const $8
I32Sub
I32Load16U $0 // PC_B
Get SP
I32Const $8
I32Sub
I32Load16U $2 // PC_F
CallIndirect $0
Drop
Get PAUSE
I32Eqz
BrIf loop
End
End
I32Const $0
Set PAUSE
Return
// wasm_export_getsp gets called from JavaScript to retrieve the SP.
TEXT wasm_export_getsp(SB),NOSPLIT,$0
Get SP
Return
TEXT runtime·pause(SB), NOSPLIT, $0-8
MOVD newsp+0(FP), SP
I32Const $1
Set PAUSE
RETUNWIND
TEXT runtime·exit(SB), NOSPLIT, $0-4
I32Const $0
Call runtime·wasmExit(SB)
Drop
I32Const $1
Set PAUSE
RETUNWIND
TEXT wasm_export_lib(SB),NOSPLIT,$0
UNDEF
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