Text file src/runtime/rt0_js_wasm.s
1 // Copyright 2018 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 #include "go_asm.h"
6 #include "textflag.h"
7
8 // _rt0_wasm_js is not used itself. It only exists to mark the exported functions as alive.
9 TEXT _rt0_wasm_js(SB),NOSPLIT,$0
10 I32Const $wasm_export_run(SB)
11 Drop
12 I32Const $wasm_export_resume(SB)
13 Drop
14 I32Const $wasm_export_getsp(SB)
15 Drop
16
17 // wasm_export_run gets called from JavaScript. It initializes the Go runtime and executes Go code until it needs
18 // to wait for an event. It does NOT follow the Go ABI. It has two WebAssembly parameters:
19 // R0: argc (i32)
20 // R1: argv (i32)
21 TEXT wasm_export_run(SB),NOSPLIT,$0
22 MOVD $runtime·wasmStack+m0Stack__size(SB), SP
23
24 Get SP
25 Get R0 // argc
26 I64ExtendI32U
27 I64Store $0
28
29 Get SP
30 Get R1 // argv
31 I64ExtendI32U
32 I64Store $8
33
34 I32Const $0 // entry PC_B
35 Call runtime·rt0_go(SB)
36 Drop
37 Call wasm_pc_f_loop(SB)
38
39 Return
40
41 // wasm_export_resume gets called from JavaScript. It resumes the execution of Go code until it needs to wait for
42 // an event.
43 TEXT wasm_export_resume(SB),NOSPLIT,$0
44 I32Const $0
45 Call runtime·handleEvent(SB)
46 Drop
47 Call wasm_pc_f_loop(SB)
48
49 Return
50
51 TEXT wasm_pc_f_loop(SB),NOSPLIT,$0
52 // Call the function for the current PC_F. Repeat until PAUSE != 0 indicates pause or exit.
53 // The WebAssembly stack may unwind, e.g. when switching goroutines.
54 // The Go stack on the linear memory is then used to jump to the correct functions
55 // with this loop, without having to restore the full WebAssembly stack.
56 // It is expected to have a pending call before entering the loop, so check PAUSE first.
57 Get PAUSE
58 I32Eqz
59 If
60 loop:
61 Loop
62 // Get PC_B & PC_F from -8(SP)
63 Get SP
64 I32Const $8
65 I32Sub
66 I32Load16U $0 // PC_B
67
68 Get SP
69 I32Const $8
70 I32Sub
71 I32Load16U $2 // PC_F
72
73 CallIndirect $0
74 Drop
75
76 Get PAUSE
77 I32Eqz
78 BrIf loop
79 End
80 End
81
82 I32Const $0
83 Set PAUSE
84
85 Return
86
87 // wasm_export_getsp gets called from JavaScript to retrieve the SP.
88 TEXT wasm_export_getsp(SB),NOSPLIT,$0
89 Get SP
90 Return
91
92 TEXT runtime·pause(SB), NOSPLIT, $0-8
93 MOVD newsp+0(FP), SP
94 I32Const $1
95 Set PAUSE
96 RETUNWIND
97
98 TEXT runtime·exit(SB), NOSPLIT, $0-4
99 I32Const $0
100 Call runtime·wasmExit(SB)
101 Drop
102 I32Const $1
103 Set PAUSE
104 RETUNWIND
105
106 TEXT wasm_export_lib(SB),NOSPLIT,$0
107 UNDEF
View as plain text