diff options
Diffstat (limited to 'src/runtime/rt0_js_wasm.s')
| -rw-r--r-- | src/runtime/rt0_js_wasm.s | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/src/runtime/rt0_js_wasm.s b/src/runtime/rt0_js_wasm.s new file mode 100644 index 0000000..714582a --- /dev/null +++ b/src/runtime/rt0_js_wasm.s @@ -0,0 +1,107 @@ +// 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 |