[llvm-dev] RFC: Need One True Way to check for -Oz/-Os (minsize, optsize) in passes...

Hal Finkel via llvm-dev llvm-dev at lists.llvm.org
Fri Jan 20 04:25:20 PST 2017

On 01/20/2017 03:11 AM, Chandler Carruth via llvm-dev wrote:
> Right now we have a healthy mixture of two ways to respond to -Oz and 
> -Os in LLVM:
> 1) Pass this info to the PassManagerBuilder and then toggle some flag 
> to the pass to change thresholds.
> 2) When running over IR, inspect it for the minsize or optsize attribute.
> Regardless of the particulars of what these mean and/or how they 
> relate to -O2 vs -O3 for example, I'd really like to at least get to 
> *one* way of doing this.
> The only way that is really compatible with LTO use cases is to use 
> the function attributes, so I'd suggest we actively work toward that. 
> That sound good to others? Thoughts?

I actually thought that (2) was already the accepted answer to this 
question. Regardless, it should be (2).


> If folks like this, I will attempt to update the few places where we 
> get this wrong. I already have some patches but wanted to make sure 
> everyone likes this direction.
> -Chandler
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Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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