[LLVMdev] Disabling certain optimizations at -O1?

[Evgeniy Stepanov]

AFAIU, it's not OK for -g to affect code generation. I agree with the
rest of your plan.


On Wed, Nov 27, 2013 at 2:16 PM, Renato Golin <renato.golin at linaro.org> wrote:
> On 27 November 2013 08:43, Evgeniy Stepanov <eugeni.stepanov at gmail.com>
> wrote:
>>
>> Also note that tail merging of calls happens in CodeGen, not in
>> SimplifyCFG.
>
>
> Hi Evgenly,
>
> What we need is the general information that we want to avoid too much code
> motion, from choosing the passes, to choosing steps on the passes, to
> lowering code differently.
>
> On the front-end layer, It's as simple as dealing -O levels.
>
> On the middle-end, we could have front-ends to set a flag "debug-illusion"
> on each individual pass, so that they could use this information to take
> decisions locally, independent of the -O level (which they don't have access
> to). This flag should only be set if the user requests -g and the
> optimization level is not greater than 1.
>
> On the back-end, I think the only place global enough that the front-end has
> access to is the Target description, which could have a similar flag to
> avoid folding too much during codegen.
>
> cheers,
> --renato