[PATCH] D119854: [SimplifyCFG][PhaseOrdering] Defer lowering switch into an integer range comparison and branch until after at least the IPSCCP

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D119854#3325875 <https://reviews.llvm.org/D119854#3325875>, @wwei wrote:

> In D119854#3325867 <https://reviews.llvm.org/D119854#3325867>, @lebedev.ri wrote:
>
>> In D119854#3325866 <https://reviews.llvm.org/D119854#3325866>, @wwei wrote:
>>
>>> @lebedev.ri Thanks for the patch. Does `convertSwitchRangeToICmp` need to be set true for O1 <https://reviews.llvm.org/owners/package/1/> pipeline? Why not keep the same with other SimplifyCFGOptions for O1 <https://reviews.llvm.org/owners/package/1/>?
>>
>> I'm not sure i understand the question.
>>
>> This change disables the transform unless it's explicitly reenabled,
>> then explicitly reenables it for all the simplifycfg pass invocations in all pipelines,
>> and then un-enables it for those simplifycfg invocations that happen before IPSCCP.
>> Function simplification pipeline is after IPSCCP, so naturally the transform is enabled there.
>
> In `buildO1FunctionSimplificationPipeline`, adding `SimplifyCFGOptions().convertSwitchRangeToICmp(true)` for all  CreateCFGSimplificationPass, I just wonder if this is necessary, since the performance for O1 <https://reviews.llvm.org/owners/package/1/> is not that important

I don't know whether or not we should be doing that for `-O1`,
but that is a separate question from the one at hand.


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https://reviews.llvm.org/D119854