Propagate constants when inlining

[MaxGraey]

@inline
function foo(x: i32): i32 {
  if (isConstant(x)) {
    return -1;
  } else {
    return x;
  }
}

export function test(): i32 {
  return foo(10);
}

produce:

(func $main/test (export "test") (type $t0) (result i32)
  i32.const 10
)

expected:

(func $main/test (export "test") (type $t0) (result i32)
  i32.const -1
)

example in playground

[dcodeIO]

That's because there are no constant locals in WASM, and after all that's still a function argument. Still, the compiler could theoretically keep track of constant arguments when inlining, but since there's no manual inlining anymore, that'd require a new mechanism.

[MaxGraey]

Oh, right! But above approach pretty useful for optimization. Will be great have such capability. Like that #32 for example.