llvm dev - Sep 2009 - [LLVMdev] Turning Off Backend Passes

So LLVMTargetMachine.cpp adds lots of transformation passes in the
various addPasses* routines.  We'd prefer not to run all of these
things (LSR, for example).  We've sort of dealt with it for now but
we'd really like to be able to turn some of these things off in a
convenient way.

We could just comment stuff out but we'd like to remain as close to
upstream as possible.  Can anyone think of a good way to provide the
needed flexibility here?  Maybe a flags that says "just do the bare 
minimum to generate code?"  Would anyone object to that?

                            -Dave

On Sep 1, 2009, at 12:07 PM, David Greene wrote:
> So LLVMTargetMachine.cpp adds lots of transformation passes in the
> various addPasses* routines.  We'd prefer not to run all of these
> things (LSR, for example).  We've sort of dealt with it for now but
> we'd really like to be able to turn some of these things off in a
> convenient way.
>
> We could just comment stuff out but we'd like to remain as close to
> upstream as possible.  Can anyone think of a good way to provide the
> needed flexibility here?  Maybe a flags that says "just do the bare
> minimum to generate code?"  Would anyone object to that?
If you have a custom compiler, why not have llvm-gcc (or whatever  
frontend you use) create its own pass manager? That way, it can  
control the exactly what passes it wants.

Evan
>
>                            -Dave
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On Tuesday 01 September 2009 14:27, Evan Cheng wrote:
> If you have a custom compiler, why not have llvm-gcc (or whatever
> frontend you use) create its own pass manager? That way, it can
> control the exactly what passes it wants.
Because addPasses* do a lot of useful stuff.  There's already a
"Fast"
flag but it's overloaded.  What if we replaced it with a bitvector of
flags?

                                -Dave