Unexpected opcode: 0xfd

[Honya2000]

Hello,

Today i tried to decompile my compiled wasm binary and got error:
02d6ac0: error: unexpected opcode: 0xfd 0x85 0x2

[sbc100]

What command are you running? Could you include the full command line and perhaps attach the binary.

It looks like 0xfd + 0x85 is the I16X8NarrowI32X4S simd instruction which it looks that wabt does support.

[sbc100]

wabt/include/wabt/opcode.def

Line 409 in 23b62e9

WABT_OPCODE(V128, ___, V128, V128, ___, 0, 0xfd, 0x85, I16X8NarrowI32X4S, "i16x8.narrow_i32x4_s", "")

[Honya2000]

Hmm. not sure why it complains then. I just pulled latest wabt and recompiled it...
I guess the issue appeared after i added Halide pipeline to my project. Will investigate in wabt under debugger and let you know.

P.S. Didn't use any command line. Just:
wasm2wat my.wasm > out.wat

[Honya2000]

Hmm, just compiled the same binary without debug info, and now it gives another opcode error:
0020b38: error: unexpected opcode: 0xfd 0x80 0x2

[Honya2000]

This part looks suspicious. Looks like it uses dynamic libs ?

[sbc100]

Can you attach the failing file?

[Honya2000]

Ok, removed dynamic lib from the binary, still the same error.
Attached binary.
Executed this way:
wasm2wat tmrwNativeAI-nt-simd.wasm > tmrwNativeAI-nt-simd.wat

tmrwNativeAI-nt-simd.zip

[sbc100]

OK, I added --enable-all and to the wasm2wat command it got a lot further.

The new error is b93575: error: unexpected opcode: 0xfd 0x3f, which looks like it should be I32X4GeS.

The error message is a actually misleading though. It seems like the bad op-code is from FP16 SIMD (Half-Precision SIMD), which wabt does not support.

Are you trying use the FP16 proposal?

[Honya2000]

I'm using Halide to process float and uint8_t buffers. It shouldn't use fp16 theoretically...
But i recently switched to new XNNPACK. Probably it uses fp16 simd, not sure...

[sbc100]

fp16 is still at phase 1 I believe so I would hope that no toolchain is enabling it by default (IIUC).

[Honya2000]

Well, maybe in this case it should throw some warnings or errors during compilation.
I'm compiling with emsdk 6.0.0 toolsets. Since i switched to 6.0.0 it allowed to use dynamic linking silently. I accidentially found dynamic libs in my binary yesterday. Probably the same situation is with SIMD...

[sbc100]

Well, maybe in this case it should throw some warnings or errors during compilation.

What is the "it" you are referring to here? Do you mean wasm2wat?

For new proposals like FP16, wabt cannot report error until somebody adds the set of opcodes for the proposal to wabt itself. For proposals that wabt has no knowledge of, all it can do is repot "unknown opcode" like this.

If you would like to add the FP16 opcodes to wabt, at least for the purposes of decoding the binary, that could be an easy enough thing to do. Feel free to send PR for that.

[Honya2000]

No, i meant emscripten compiler should report warning of course.
I just don't know which code produces wrong opcode, since lot of functions use SIMD.

Tried to play with differed simd related compiler options - still the same:
0b87f2d: error: unexpected opcode: 0xfd 0x3f