LTO temp commands

Subprojects LLD
1

Hi,

How could I emit commands used to generate LTO temp files including preopt.bc, internalize.bc, opt.bc, precodegen.bc and lto.o?

Thanks,
Anshil

2

What linker are you using? For lld this would be --save-temps (-Wl,–save-temps via the clang driver). For gold/bfd it would be -Wl,–plugin-opt=save-temps.

3

I am using lld. How could I collect the commands used to generate these temps though?

4

| gandhi56
October 13 |

  • | - |

I am using lld. How could I collect the commands used to generate these temps though?

Not sure what you mean by “collect the commands” - collect from where?

5

@teresajohnson I would like to know how the temps are created. What passes run to create preopt.bc, internalize.bc, opt.bc and so on.

6

They are dumped via hooks.

See the following for the function that sets up the hooks (invoked by the linkers): https://github.com/llvm/llvm-project/blob/4b8f23e93de56b7bfeffbf789ec5a75525dc5d88/llvm/lib/LTO/LTOBackend.cpp#L87

The hooks set up there are invoked at several points during the LTO process. See lib/LTO/LTO.cpp and lib/LTO/LTOBackend.cpp for the calls to the *ModuleHook callbacks:
https://github.com/search?q=repo%3Allvm%2Fllvm-project%20"ModuleHook(%22&type=code

1 Like
7

Ahh, I see. That’s helpful, thank you!