The reference interpreter became up to 20 times slower after a87fffc

While experimenting with the reference interpreter on binaries produced by Kotlin, I noticed a huge performance degradation.
It seems it is due to some changes introduced in a87fffc.

To reproduce it, please run a wasm file index.wasm.zip in reference interpreter with the following command:

'wasm' index.wasm -t -e '(module instance) (invoke "_initialize") (invoke "runBoxTest")'

Here are some runs with different versions:

a87fffc

$ time '_build/a8/wasm.exe' index.wasm -t -e '(module instance) (invoke "_initialize") (invoke "runBoxTest")'
-- Running ("(input \"index.wasm\")")...
-- Parsing...
-- Running...
-- Loading (index.wasm)...
-- Decoding...
-- Running...
-- Decoding...
-- Checking...
-- Running ("(module instance) (invoke \"_initialize\") (invoke \"runBoxTest\")")...
-- Parsing...
-- Running...
-- Initializing...
-- Invoking function "_initialize"...
-- Invoking function "runBoxTest"...
1 : [i32]
'a8/wasm.exe'  -t -e   12.65s user 1.27s system 97% cpu 14.212 total

d0eee4a

$ time '_build/d0/wasm.exe' index.wasm -t -e '(module instance) (invoke "_initialize") (invoke "runBoxTest")'
-- Running ("(input \"index.wasm\")")...
-- Parsing...
-- Running...
-- Loading (index.wasm)...
-- Decoding...
-- Running...
-- Decoding...
-- Checking...
-- Running ("(module instance) (invoke \"_initialize\") (invoke \"runBoxTest\")")...
-- Parsing...
-- Running...
-- Initializing...
-- Invoking function "_initialize"...
-- Invoking function "runBoxTest"...
1 : [i32]
'_build/d0/wasm.exe'  -t -e   0.65s user 0.02s system 73% cpu 0.919 total

d79e5c8

$ time '_build/d7/wasm.exe' index.wasm -t -e '(module instance) (invoke "_initialize") (invoke "runBoxTest")'
-- Running ("(input \"index.wasm\")")...
-- Parsing...
-- Running...
-- Loading (index.wasm)...
-- Decoding...
-- Running...
-- Decoding...
-- Checking...
-- Running ("(module instance) (invoke \"_initialize\") (invoke \"runBoxTest\")")...
-- Parsing...
-- Running...
-- Initializing...
-- Invoking function "_initialize"...
-- Invoking function "runBoxTest"...
1 : [i32]
'_build/d7/wasm.exe'  -t -e   0.65s user 0.02s system 78% cpu 0.860 total

Use the provided index.wasm and the shown wasm command as the reproduction entry point. Compare builds at a87fffc, d0eee4a, and d79e5c8, then profile or bisect the regression. Done means the reference interpreter no longer shows the reported slowdown while preserving the command's result, 1 : [i32].