feat(llvm): Pass global #0 and memory #0 as parameters between guest functions

[xdoardo]

(closes #5493 #5494)

This PR adds the --enable-pass-params-opt flag to the CLI and the enable_pass_params_opt() function to the LLVM compiler.

This optimization is turned off by default. It assumes that the Wasm module to compile has both a global (g0) and a memory (m0) defined in it. The objective of the optimization is that of passing the value of g0 and a pointer to the base of m0 as parameters between guest functions, in order to reduce the overhead of loading these values through (multiple) pointers (i.e., loads in the generated code).

Pitfalls

In some cases this optimization works very well, speeding up the execution times of modules such as php:

$ wasmer-dev run --registry=wasmer.io --llvm php/[email protected] --mapdir=./app:. -- app/bench.php
-------------------------------------------------------
|       PHP BENCHMARK SCRIPT v.2.0 by @SergiX44       |
-------------------------------------------------------
     ...
-------------------------------------------------------
Total time.................................... 5.0362 s
Peak memory usage................................ 0 MiB

vs

$ wasmer-dev run --registry=wasmer.io --llvm --enable-pass-params-opt php/[email protected] --mapdir=./app:. -- app/bench.php
-------------------------------------------------------
|       PHP BENCHMARK SCRIPT v.2.0 by @SergiX44       |
-------------------------------------------------------
    ...
Total time.................................... 2.9245 s
Peak memory usage................................ 0 MiB

In some other cases, passing g0 and m0 as parameters can be actually an hindrance, making the execution slower. In my opinion, this is due to the fact that g0 and m0 are passed as second and third parameters to generated guest functions, which might cause other parameters to be spilled onto the stack. Thus, depending on which of g0, m0 or the other spilled parameters is used more, this optimization might actually slow things down.

[promptless]

📝 Documentation updates detected! A separate PR for documentation updates has been made here: wasmerio/docs.wasmer.io#126