This will make it easy for callers to see issues with and fix up calls
to createTargetMachine after a future change to the params of
TargetMachine.
This matches other nearby enums.
For downstream users, this should be a fairly straightforward
replacement,
e.g. s/CodeGenOpt::Aggressive/CodeGenOptLevel::Aggressive
or s/CGFT_/CodeGenFileType::
There were quite a few places in the tutorial where the snippets were not up to date with the full code listings given. I have updated all of the ones I could find, which mostly involves changing `.` to `->` when accessing through a `std::unique_ptr`, changing `while (1)` to `while (true)`, and other such small changes.
There are still however a few places where I am not sure what to do, such as:
- Chapter 4: `ParseTopLevelExpr()` in chapter 3 sets the ProtoTypeAST
name to "", however it is referred to as "__anon_expr"
in chapter 4. Would it be required to mention this change
in chapter 4?
- Chapter 9: The code snippets refer to the top level expression as
"main", however the full code listing refers to it as
"__anon_expr". I think given the context of the chapter
it makes sense to refer to it as "main", so I have
updated the code listing to reflect that.
- Chapter 9: In chapter 9 the diff given for `HandleTopLevelExpression()`
deletes code that is not mentioned anywhere else, so I am
not sure what is to be done there.
- Miscellaneous: I don't think this is very important, however the
casing used for the first word of error messages
tends to vary between upper and lower case between
chapters and I do not know if it is worth reconciling
these differences.
Reviewed By: xgupta
Differential Revision: https://reviews.llvm.org/D142323
Avoids the need to include TargetMachine.h from various places just for
an enum. Various other enums live here, such as the optimization level,
TLS model, etc. Data suggests that this change probably doesn't matter,
but it seems nice to have anyway.
