llvm dev - Jan 2019 - Removing LLVM_ALWAYS_INLINE from ADT classes

On Mon, Jan 7, 2019 at 8:39 AM <paul.robinson at sony.com> wrote:
>
>
> > -----Original Message-----
> > From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf
Of
> Alex
> > Bradbury via llvm-dev
> > Sent: Monday, January 07, 2019 11:33 AM
> > To: Mehdi AMINI
> > Cc: LLVM Dev
> > Subject: Re: [llvm-dev] Removing LLVM_ALWAYS_INLINE from ADT classes
> >
> > On Sun, 6 Jan 2019 at 00:42, Mehdi AMINI via llvm-dev
> > <llvm-dev at lists.llvm.org> wrote:
> > >
> > >
> > >
> > > On Fri, Jan 4, 2019 at 3:52 PM Paweł Bylica via llvm-dev
<llvm-
> > dev at lists.llvm.org> wrote:
> > >>
> > >> On Sat, Jan 5, 2019 at 12:38 AM Duncan P. N. Exon Smith via
llvm-dev
> > <llvm-dev at lists.llvm.org> wrote:
> > >>>
> > >>> This makes sense to me.
> > >>>
> > >>> One concern is that this in itself will slow down the
build, since
> > tablegen will get even slower.  Ideally, there would be some (perhaps
> > default?) configuration where we build the tablegen binaries with
> > optimizations on and then use them in the build, as if we were cross-
> > compiling.
> > >>
> > >>
> > >> Maybe something simple like -DLLVM_OPTIMIZE_TABLEGEN=ON
(enabled by
> > default for Debug builds). You would need to set it to off only if you
> > want to debug tablegen.
> > >
> > >
> > > I proposed this a while back, but it think there were some
problems
> with
> > it, I don't remember what exactly but maybe related to
bootstrapping / 2-
> > stages builds?
> > >
> > > + Chris, maybe he remembers something?
> >
> > LLVM_OPTIMIZED_TABLEGEN=ON is a handy way of speeding up build times,
> > but it really shouldn't be recommended for anyone who is modifying
.td
> > files. You run the risk of making .td modifications that trigger
> > asserts for those not using LLVM_OPTIMIZED_TABLEGEN.
>
> Can we make LLVM_OPTIMIZED_TABLEGEN=ON build it as Release+Asserts?

There is (use to be) some very expensive assertions in llvm-tblgen.

—
Mehdi
>
> --paulr
>
> >
> > Best,
> >
> > Alex
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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I believe the issues about Debug config and Visual Studio can be solved by
using generator expressions

$<$<CONFIG:Debug>:-O2>

or alternatively CMAKE_CXX_CLAGS_DEBUG.

At first we don't have to modify the assertions build option so if Debug
config builds with assertions tablegen will be build with as well.

Also we can start with keeping LLVM_OPTIMIZE_TABLEGEN off by default.

If that sounds good, I can come with a prototype later.

// P.

On Mon, Jan 7, 2019 at 5:54 PM Mehdi AMINI via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
>
>
> On Mon, Jan 7, 2019 at 8:39 AM <paul.robinson at sony.com> wrote:
>
>>
>>
>> > -----Original Message-----
>> > From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On
Behalf Of
>> Alex
>> > Bradbury via llvm-dev
>> > Sent: Monday, January 07, 2019 11:33 AM
>> > To: Mehdi AMINI
>> > Cc: LLVM Dev
>> > Subject: Re: [llvm-dev] Removing LLVM_ALWAYS_INLINE from ADT
classes
>> >
>> > On Sun, 6 Jan 2019 at 00:42, Mehdi AMINI via llvm-dev
>> > <llvm-dev at lists.llvm.org> wrote:
>> > >
>> > >
>> > >
>> > > On Fri, Jan 4, 2019 at 3:52 PM Paweł Bylica via llvm-dev
<llvm-
>> > dev at lists.llvm.org> wrote:
>> > >>
>> > >> On Sat, Jan 5, 2019 at 12:38 AM Duncan P. N. Exon Smith
via llvm-dev
>> > <llvm-dev at lists.llvm.org> wrote:
>> > >>>
>> > >>> This makes sense to me.
>> > >>>
>> > >>> One concern is that this in itself will slow down the
build, since
>> > tablegen will get even slower.  Ideally, there would be some
(perhaps
>> > default?) configuration where we build the tablegen binaries with
>> > optimizations on and then use them in the build, as if we were
cross-
>> > compiling.
>> > >>
>> > >>
>> > >> Maybe something simple like -DLLVM_OPTIMIZE_TABLEGEN=ON
(enabled by
>> > default for Debug builds). You would need to set it to off only if
you
>> > want to debug tablegen.
>> > >
>> > >
>> > > I proposed this a while back, but it think there were some
problems
>> with
>> > it, I don't remember what exactly but maybe related to
bootstrapping /
>> 2-
>> > stages builds?
>> > >
>> > > + Chris, maybe he remembers something?
>> >
>> > LLVM_OPTIMIZED_TABLEGEN=ON is a handy way of speeding up build
times,
>> > but it really shouldn't be recommended for anyone who is
modifying .td
>> > files. You run the risk of making .td modifications that trigger
>> > asserts for those not using LLVM_OPTIMIZED_TABLEGEN.
>>
>> Can we make LLVM_OPTIMIZED_TABLEGEN=ON build it as Release+Asserts?
>
>
> There is (use to be) some very expensive assertions in llvm-tblgen.
>
> —
> Mehdi
>
>>
>> --paulr
>>
>> >
>> > Best,
>> >
>> > Alex
>> > _______________________________________________
>> > LLVM Developers mailing list
>> > llvm-dev at lists.llvm.org
>> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Historically there was a request to make LLVM_OPTIMIZED_TABLEGEN On by default
for debug builds, which I discouraged. At the time it was suggested that
workflow was fairly new and untested in a lot of build configurations. Today I
believe that situation is slightly better.

I believe there are still issues with it not working correctly in the Xcode
generator, but I know people have used it successfully with Visual Studio.

I think that enabling it by default in Debug builds is probably reasonable for
most generators, but anyone looking to make that change should expect some bumps
in the road.

-Chris
> On Jan 7, 2019, at 9:03 AM, Paweł Bylica via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> I believe the issues about Debug config and Visual Studio can be solved by
using generator expressions
> $<$<CONFIG:Debug>:-O2>
> or alternatively CMAKE_CXX_CLAGS_DEBUG.
> 
> At first we don't have to modify the assertions build option so if
Debug config builds with assertions tablegen will be build with as well.
> 
> Also we can start with keeping LLVM_OPTIMIZE_TABLEGEN off by default.
> 
> If that sounds good, I can come with a prototype later.
> 
> // P.
> 
> On Mon, Jan 7, 2019 at 5:54 PM Mehdi AMINI via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> 
> 
> On Mon, Jan 7, 2019 at 8:39 AM <paul.robinson at sony.com
<mailto:paul.robinson at sony.com>> wrote:
> 
> 
> > -----Original Message-----
> > From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org
<mailto:llvm-dev-bounces at lists.llvm.org>] On Behalf Of Alex
> > Bradbury via llvm-dev
> > Sent: Monday, January 07, 2019 11:33 AM
> > To: Mehdi AMINI
> > Cc: LLVM Dev
> > Subject: Re: [llvm-dev] Removing LLVM_ALWAYS_INLINE from ADT classes
> > 
> > On Sun, 6 Jan 2019 at 00:42, Mehdi AMINI via llvm-dev
> > <llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>> wrote:
> > >
> > >
> > >
> > > On Fri, Jan 4, 2019 at 3:52 PM Paweł Bylica via llvm-dev
<llvm-
> > dev at lists.llvm.org <mailto:dev at lists.llvm.org>> wrote:
> > >>
> > >> On Sat, Jan 5, 2019 at 12:38 AM Duncan P. N. Exon Smith via
llvm-dev
> > <llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>> wrote:
> > >>>
> > >>> This makes sense to me.
> > >>>
> > >>> One concern is that this in itself will slow down the
build, since
> > tablegen will get even slower.  Ideally, there would be some (perhaps
> > default?) configuration where we build the tablegen binaries with
> > optimizations on and then use them in the build, as if we were cross-
> > compiling.
> > >>
> > >>
> > >> Maybe something simple like -DLLVM_OPTIMIZE_TABLEGEN=ON
(enabled by
> > default for Debug builds). You would need to set it to off only if you
> > want to debug tablegen.
> > >
> > >
> > > I proposed this a while back, but it think there were some
problems with
> > it, I don't remember what exactly but maybe related to
bootstrapping / 2-
> > stages builds?
> > >
> > > + Chris, maybe he remembers something?
> > 
> > LLVM_OPTIMIZED_TABLEGEN=ON is a handy way of speeding up build times,
> > but it really shouldn't be recommended for anyone who is modifying
.td
> > files. You run the risk of making .td modifications that trigger
> > asserts for those not using LLVM_OPTIMIZED_TABLEGEN.
> 
> Can we make LLVM_OPTIMIZED_TABLEGEN=ON build it as Release+Asserts?
> 
> There is (use to be) some very expensive assertions in llvm-tblgen.
> 
> — 
> Mehdi
> 
> --paulr
> 
> > 
> > Best,
> > 
> > Alex
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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