llvm dev - Oct 2020 - TableGen -time-regions option

I'm pondering a new timing feature for TableGen and am wondering whether
anyone uses the existing -time-regions option. Some instrumentation for it
appears in CodeGenTarget.cpp and GICombinerEmitter.cpp but nowhere else. If no
one is using it, I'll be tempted to remove it.

> On Oct 25, 2020, at 5:08 PM, Paul C. Anagnostopoulos via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> 
> I'm pondering a new timing feature for TableGen and am wondering
whether anyone uses the existing -time-regions option. Some instrumentation for
it appears in CodeGenTarget.cpp and GICombinerEmitter.cpp but nowhere else. If
no one is using it, I'll be tempted to remove it.
I’m not hearing anyone jump up and down about this - go for it Paul,

-Chris

It is on my to-do list. Thanks!

At 10/31/2020 03:26 PM, Chris Lattner wrote:

>> On Oct 25, 2020, at 5:08 PM, Paul C. Anagnostopoulos via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>> 
>> I'm pondering a new timing feature for TableGen and am wondering
whether anyone uses the existing -time-regions option. Some instrumentation for
it appears in CodeGenTarget.cpp and GICombinerEmitter.cpp but nowhere else. If
no one is using it, I'll be tempted to remove it.
>
>I’m not hearing anyone jump up and down about this - go for it Paul,
>
>-Chris

Hi Paul,

I'm rather late to the thread but I added the existing -time-regions option
when I was debugging a particularly nasty perf problem in TableGen. I really
only use it when we have a perf problem downstream.

The main thing I was getting out of it was the ability to annotate periods of
time in Xcode Instruments just by adding a NamedRegionTimer to the right
function/block (see
https://reviews.llvm.org/rGe1414d176048c1f24fc3f54bb923fb48a2b985a3). That
helped me track down the work that was taking the time and let me filter out the
noise from elsewhere so I could look at the relevant memory allocations+churn.
Feel free to change it but I'd like to keep that Instruments integration if
we can as I'm sure we'll hit another perf problem sooner or later.
> On 25 Oct 2020, at 17:08, Paul C. Anagnostopoulos via llvm-dev <llvm-dev
at lists.llvm.org> wrote:
> 
> I'm pondering a new timing feature for TableGen and am wondering
whether anyone uses the existing -time-regions option. Some instrumentation for
it appears in CodeGenTarget.cpp and GICombinerEmitter.cpp but nowhere else. If
no one is using it, I'll be tempted to remove it.
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

The new timing feature lets you insert timers anywhere you want. Each timer
stops the previous one. If there are no timers in the backend, then TableGen
times the overall backend.

I've used the new feature to locate the bottleneck in the -emit-dag-isel
backend.

At 11/13/2020 10:52 PM, Daniel Sanders wrote:
>Hi Paul,
>
>I'm rather late to the thread but I added the existing -time-regions
option when I was debugging a particularly nasty perf problem in TableGen. I
really only use it when we have a perf problem downstream.
>
>The main thing I was getting out of it was the ability to annotate periods
of time in Xcode Instruments just by adding a NamedRegionTimer to the right
function/block (see
https://reviews.llvm.org/rGe1414d176048c1f24fc3f54bb923fb48a2b985a3). That
helped me track down the work that was taking the time and let me filter out the
noise from elsewhere so I could look at the relevant memory allocations+churn.
Feel free to change it but I'd like to keep that Instruments integration if
we can as I'm sure we'll hit another perf problem sooner or later.

----------------------------------------------------------------
Windfall               Paul C. Anagnostopoulos 
      ----------------------------------------------------------
   Software            978 369-0839
                             www.windfall.com
----------------------------------------------------------------
My life has been filled with calamities,
some of which actually happened.
---Mark Twain 

Guga 'mzimba, sala 'nhliziyo

Ah, I spoke too soon. Let me investigate how the new feature works with
Instruments and then I will enhance it if necessary.

At 11/13/2020 10:52 PM, Daniel Sanders wrote:
>Hi Paul,
>
>I'm rather late to the thread but I added the existing -time-regions
option when I was debugging a particularly nasty perf problem in TableGen. I
really only use it when we have a perf problem downstream.
>
>The main thing I was getting out of it was the ability to annotate periods
of time in Xcode Instruments just by adding a NamedRegionTimer to the right
function/block (see
https://reviews.llvm.org/rGe1414d176048c1f24fc3f54bb923fb48a2b985a3). That
helped me track down the work that was taking the time and let me filter out the
noise from elsewhere so I could look at the relevant memory allocations+churn.
Feel free to change it but I'd like to keep that Instruments integration if
we can as I'm sure we'll hit another perf problem sooner or later.