Unable to profile wasm build on Chrome

[Amit Gupta]

I am trying to profile my wasm build on Chrome using JavaScript Profiler. The code itself is working fine. When I record a snapshot of page load and analyse it, all the function names are coming to be <wasm-unnamed>. This is happening 90% of times. 1-2 times, it worked fine. This is causing ambiguous behaviour. I am using 1.38.28 version of emsdk and Chrome version is Version 80.0.3987.162 (Official Build) (64-bit). Can someone suggest what is happening here? Same issue is happening on Chrome Canary and latest Edge browser too.

[Shachar Langbeheim]

are you compiling and linking with -g --profiling? That should keep the symbols.

On Thu, 2 Apr 2020 at 13:59, Amit Gupta <amitgu...@gmail.com> wrote:

I am trying to profile my wasm build on Chrome using JavaScript Profiler. The code itself is working fine. When I record a snapshot of page load and analyse it, all the function names are coming to be <wasm-unnamed>. This is happening 90% of times. 1-2 times, it worked fine. This is causing ambiguous behaviour. I am using 1.38.28 version of emsdk and Chrome version is Version 80.0.3987.162 (Official Build) (64-bit). Can someone suggest what is happening here? Same issue is happening on Chrome Canary and latest Edge browser too.

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[Alon Zakai]

Correct, but note that --profiling is enough, as -g also emits DWARF debug info, which can do a lot more (but increases build size and may inhibit some optimizations).

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[Amit Gupta]

Yes, I am using --profiling --profiling-funcs flags.

[Alon Zakai]

That's very strange. Is it possible an older build is loaded by the profiler (maybe it's in the cache?). Try building to a new name and profiling that maybe.

To see exactly what's going on, you can run wasm-dis or wasm2wat to disassemble the wasm file, and see if functions have names there. For example, here is what things look like on a hello world program without and with --profiling:

-  (import "wasi_snapshot_preview1" "fd_write" (func $fimport$0 (param i32 i32 i32 i32) (result i32)))

+  (import "wasi_snapshot_preview1" "fd_write" (func $__wasi_fd_write (param i32 i32 i32 i32) (result i32)))

- (export "__wasm_call_ctors" (func $1))

+ (export "__wasm_call_ctors" (func $__wasm_call_ctors))

- (func $1 (; 6 ;)
+ (func $__wasm_call_ctors (; 6 ;)

-    (call $fimport$3)
+    (call $__handle_stack_overflow)

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[Amit Gupta]

I don't think the profiler is loading an old build since I hard reloaded the browser and also disabled catching in Network tab in devtools. I can give wasm-dis or wasm2wat  a try.

On Thursday, 2 April 2020 16:29:29 UTC+5:30, Amit Gupta wrote: