[LLVMdev] RFC: GLIBCXX_DEBUG ScheduleDAG Patch

Evan Cheng
Fri, 04 Jan 2008 18:59:20 -0000

On Jan 2, 2008, at 12:44 PM, David Greene wrote:

> On Saturday 22 December 2007 02:33, Evan Cheng wrote:
>
>>> After some very simple testing, I see slowdowns of around 1.7%.  I
>>> assume
>>> this is ok, but want to check.
>>
>> Can you clarify? Is this 1.7% slowdown of scheduling time or overall
>> codegen time? If it's the later, then it seems a bit too much.
Also,
>> please test it with all the MultiSource/Applications.
>
> It's 1.7% overall.

That seems somewhat steep. Can you see how much of the scheduling
slow down there is?

>
> Does the nightly test build provide compile-time information?  I
> see from
> the Makefile that it uses -time-passes.  I assume the "Today's LLC
> compile"
> header on the nightly page comes from that and reflects the compile
> time
> for the test.

The better way is to add a custom report for this. See
TEST.llc.Makefile and TEST.llc.report under llvm-test as an example.
You can do make TEST=llc to generate custom reports. If this change
can somehow be optionally controlled, then you can set it as llcbeta
option and write a custom report that compare the time spend in some
particular passes (TEST.beta-compare is an example, but it comparesf
number instructions).

The biggest problem is right now time spent in scheduling is lumped
into "DAG->DAG Instruction Selection" time because it's part of
the
pass. It would be nice if we can somehow bring it out.

Evan

>
>                                           -Dave
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