✔ as help about utf8_to_latin1. · general

#0  0x00000040008a96e6 in wasmtime_runtime::component::transcode::trampolines::utf8_to_latin1 (src=0x40c3ac5000, len=27, dst=0x4043ab5000, _retptr=0x0)
    at src/component/transcode.rs:88
#1  0x0000004043ab3064 in ?? ()

you can see _retptr is null.
this bug is very wired to me.
I nerve find the code in wasmtime that you want to call wasmtime_runtime::component::transcode::trampolines::utf8_to_latin1 .
I only saw you want to call wasmtime_cranelift::compiler::component::host::utf8_to_latin1.
and the two function have differrent signature.
I think you are calling the wrong function???

xxxxxxxxxxxxxxxxxxx : Utf8ToLatin1 function u0:0(i64 vmctx, i64, i32, i32, i32) -> i32, i32 wasmtime_system_v {
    sig0 = (i64, i64, i64) -> i64, i64 wasmtime_system_v

block0(v0: i64, v1: i64, v2: i32, v3: i32, v4: i32):
    v5 = load.i64 notrap aligned v0+32
    v6 = get_frame_pointer.i64
    v7 = load.i64 notrap aligned v6
    store notrap aligned v7, v5+24
    v8 = get_return_address.i64
    store notrap aligned v8, v5+32
    v9 = load.i64 notrap aligned v0+8
    v10 = load.i64 notrap aligned v9+64
    v11 = load.i64 notrap aligned v0+144
    v12 = load.i64 notrap aligned v11
    v13 = load.i64 notrap aligned v0+152
    v14 = load.i64 notrap aligned v13
    v15 = uextend.i64 v2
    v16 = iadd v12, v15
    v17 = uextend.i64 v3
    v18 = uextend.i64 v4
    v19 = iadd v14, v18
    v20, v21 = call_indirect sig0, v10(v16, v17, v19)  // call to  wasmtime_runtime::component::transcode::trampolines::utf8_to_latin1
    v22 = ireduce.i32 v20
    v23 = ireduce.i32 v21
    return v22, v23
}

Chris Fallin (Aug 15 2022 at 05:44):

@yang yu The component-model stuff is pretty new; @Alex Crichton might have more specific insights or hints here?

yang yu (Aug 15 2022 at 06:11):

Alex Crichton (Aug 15 2022 at 14:34):

This most likely has to do with the multi-return and the wasmtime_system_v ABI in use here. The "wasmtime flavor" of the systemv_abi changes how multiple returns get represented. Has the riscv64 backend implemented this ABI? Are the other multi-value tests passing in Wasmtime yet (I would expect them not to be passing if this isn't passing)

yang yu (Aug 16 2022 at 02:54):

Chris Fallin (Aug 16 2022 at 05:53):

@yang yu the wasmtime_system_v ABI is our own invention; there won't be any other docs about it. Basically what is needed is to support multivalue returns in a slightly different way that involves a stack return area. If you grep for WasmtimeSystemV in x64/abi.rs you'll see how we handle it on x86-64; most of the details will be handled by the common ABI code

yang yu (Aug 18 2022 at 01:19):

@Chris Fallin there is another detail I don't know.
wasmtime_system_v abi only use one register store result.
image.png

Notification Bot (Aug 18 2022 at 01:19):

Notification Bot (Aug 21 2022 at 03:37):

yang yu (Aug 21 2022 at 04:08):

is that wasmtime_system_abi is actual C api, because C only can return one value.
So only one register can be used for all register class to return value.

bjorn3 (Aug 21 2022 at 08:20):

wasmtime_system_v is basically system_v except in case of returning multiple values it passes a pointer to write the return values to as last argument afaik.

yang yu (Aug 22 2022 at 03:59):

@bjorn3 ok，I just have this question , I saw using wasmtime_system_v to call C code.

Stream: general

Topic: ✔ as help about utf8_to_latin1.

yang yu (Aug 15 2022 at 05:13):