Compiling WASM to AOT loses the import table.

[AY268]

I compiled a WASM file to an AOT file using WAMRC, which only has one import table.

However, when I debug it, I find that module->import_table_count is always 0 in the file wasm-micro-runtime/core/iwasm/aot/aot_loader.c, the function load_table_info, while module->table_count is 1.

This is how I compile it: wamrc --bounds-checks=1 --target=aarch64 -o output.aot output.wasm.

I wonder how this happens, and how I could solve it.

[TianlongLiang]

The import table in aot isn't fully functional yet, which is why you see the discrepancy here, may I ask your use case? There may be a workaround for your use case

[AY268]

I use this small WAT module:
(module (import "env" "table" (table 10 funcref)) )
and compile it to wasm:
wat2wasm import_table.wat -o import_table.wasm
then to aot:
wamrc --bounds-checks=1 --target=aarch64 -o import_table.aot import_table.wasm

And my build configuration is:

-- Build Configurations:
     Build as target AARCH64
     CMAKE_BUILD_TYPE RelWithDebInfo
     WAMR Interpreter enabled
     WAMR AOT enabled
     WAMR Fast JIT disabled
     WAMR LLVM ORC JIT disabled
     Libc builtin enabled
     Libc WASI enabled
     Fast interpreter enabled
     Multiple modules disabled
     Bulk memory feature enabled
     Hardware boundary check disabled
     Wakeup of blocking operations enabled
     Reference types disabled
     GC performance profiling disabled
     Load custom section enabled
     Module instance context enabled
     Quick AOT/JIT entries enabled
     AOT intrinsics enabled
-- Configuring done (0.0s)
-- Generating done (0.0s)

[AY268]

Also I meet another question when using AOT.
When I try to use a custom section, I find that it never enters the branch load_custom_section in the function load_from_sections(in file wasm-micro-runtime/core/iwasm/aot/aot_loader.c).
I would like to know the reason for this.

The module I used is:
(module (custom "test" (data "\57\65\62\41\73\73\65\6D\62\6C\79")) )

[TianlongLiang]

Hi, could you print more log for the custom section?
For example:

iwasm -v=5 test.aot

[AY268]

Of course, I'd like to show you more logs. However, I compiled and ran it on Android, using libiwasm.so. Could you tell me how to print more logs for libiwasm.so?

More details about the custom section is that I found that it may not support compiling WAT with a custom section into WASM.
I get the wasm file from customSections.any.js, the Custom sections with surrogate pairs test.
I only change the name of the custom section, and compile it to AOT myself.
I'm not sure whether this is the problem.

Really thank you for your help. If you have any ideas about the custom section issue or the import table issue, please let me know. Thanks again.

[TianlongLiang]

About import table, it will be functional and used as your example after the development of instnatiation linking, which could take some time.

For printing logs, you can use wasm_runtime_set_log_level(5) to set log level to verbose

[AY268]

Thanks for your answer.
I can only use wasm_runtime_set_log_level(WASM_LOG_LEVEL_VERBOSE); to set the log level.

For the custom section test, the log is as follows:

    I  [14:38:19:363 - 734F7D3ED0]: 
    I  Load module success.
    I  
    I  [14:38:19:363 - 734F7D3ED0]: 
    I  warning: wasm_runtime_free with NULL pointer
    I  

[TianlongLiang]

About the custom section:
Did you add the option --emit-custom-sections= for wamrc? For details you can refer to wamrc --help:

  --emit-custom-sections=<section names>
                            Emit the specified custom sections to AoT file, using comma to separate
                            multiple names, e.g.
                                --emit-custom-sections=section1,section2,sectionN

I tested it on my local machine, and the aot file will have the custome section.

[AY268]

This is actually the solution! Really thanks for your help!

[TianlongLiang]

No worries, I am glad it works

[AY268]

@TianlongLiang
Hi, I still have a question about importing tables/memory in AOT.
I found that when I compile the two WAT files to WASM, and then to AOT, they are different in the WASM files but the same in the AOT files.

(module
  (import "env" "memory" (memory 1 2))
)

(module
  (memory 1 2)
)

I don't know whether it's my fault that I should add some options but didn't, or if it is designed like this now.

The command I used is as follows:

wat2wasm test.wat -o test.wasm
wamrc --bounds-checks=1 --target=aarch64 -o test.aot test.wasm

Could you give some help again?

[TianlongLiang]

Basically, if you want to import and share the globals/tables/memories among your wasm apps, it needs instnatiation linking, and it isn't supported now.

And if you don't have share demand, treating an import as a non-import is the same thing, that's what WAMR does now(in aot compiler) and it complies with your observation.