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Re: [RFC] Track discriminators by instruction instead of by basic block
On Thu, Nov 12, 2009 at 8:44 PM, Cary Coutant <ccoutant@google.com> wrote:
>> How much more memory do we need when keeping discriminators
>> with LTO (which you don't - patches to lto-streamer-{in,out} are missing).
>
> I'm thinking of leaving build_cfg the way it is currently (where it
> assigns discriminators to basic blocks as necessary), but move the
> mechanics of assigning the discriminators to individual instructions
> down to the fixup_cfg pass. The earliest we actually use the
> discriminators is in tree_profile, so that gets the discriminators
> assigned just before we use them, and it means that the assignment
> happens after lto-streamer-in, so I don't need to stream out the
> per-instruction discriminator information. I'll still need to stream
> the per-basic-block discriminator info out in output_cfg(), but that's
> fairly easy, and adds only one byte (discriminators are small and
> usually 0) per basic block.
I don't think that observation is correct (that tree-profile is after
streaming in).
Richard.
> Does that sound reasonable?
>
> -cary
>