PossibleContents + ContentOracle (#4685)

This pulls out the core PossibleContents and ContentOracle classes from the
very large #4598, making a smaller PR that can be reviewed first. This includes
unit tests for the code, but comprehensive testing will only appear in the later
PR, when a new pass is added that uses all this.

PossibleContents tracks the possible contents at particular locations in the
program. It can track constant values as well as "this must contain this
exact type", which is more than wasm itself can indicate.

*Location structs are provided to declare locations in the wasm, like the
location of a local or of a function argument.

ContentOracle analyzes the entire program, and can then map a Location
to the PossibleContents there, which a later pass will use to optimize.

0 files changed, 0 insertions, 0 deletions