This feature is enabled by `-codegen-data-thinlto-two-rounds`, which
effectively runs the `-codegen-data-generate` and `-codegen-data-use` in
two rounds to enable global outlining with ThinLTO.
1. The first round: Run both optimization + codegen with a scratch
output.
Before running codegen, we serialize the optimized bitcode modules to a
temporary path.
2. From the scratch object files, we merge them into the codegen data.
3. The second round: Read the optimized bitcode modules and start the
codegen only this time.
Using the codegen data, the machine outliner effectively performs the
global outlining.
Depends on #90934, #110461 and #110463.
This is a patch for
https://discourse.llvm.org/t/rfc-enhanced-machine-outliner-part-2-thinlto-nolto/78753.
Reland [CGData] llvm-cgdata #89884 using `Opt` instead of `cl`
- Action options are required, `--convert`, `--show`, `--merge`. This
was similar to sub-commands previously implemented, but having a prefix
`--`.
- `--format` option is added, which specifies `text` or `binary`.
---------
Co-authored-by: Kyungwoo Lee <kyulee@fb.com>
