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Xinliang David Li

2015-Jun-24 21:16 UTC

[LLVMdev] Inline hint for methods defined in-class

On Wed, Jun 24, 2015 at 2:10 PM, Robinson, Paul
<Paul_Robinson at playstation.sony.com> wrote:>> -----Original Message-----
>> From: Easwaran Raman [mailto:eraman at google.com]
>> Sent: Wednesday, June 24, 2015 1:27 PM
>> To: Xinliang David Li
>> Cc: Robinson, Paul; Xinliang David Li; <llvmdev at cs.uiuc.edu>
List
>> Subject: Re: [LLVMdev] Inline hint for methods defined in-class
>>
>> The method to identify functions with in-class definitions is one part
>> of my question. Even if there is a way to do that without passing the
>> hint, I'm interested in getting feedback on treating it at-par with
>> functions having the inline hint in inline cost analysis.
>
> Well, personally I think having the 'inline' keyword mean "try
harder"
> is worth something, but that's intuition backed by no data whatsoever.
> Your patch would turn 'inline' into noise, when applied to a
function
> with an in-class definition.  Granted that the way the C++ standard
> describes 'inline' it is effectively noise in that situation.
> --paulr
You are assuming most of the functions are defined in-class, which I
think is not true.

David
>
>>
>> Thanks,
>> Easwaran
>>
>>
>> On Wed, Jun 24, 2015 at 12:56 PM, Xinliang David Li
>> <xinliangli at gmail.com> wrote:
>> > The problem is that the other way around is not true: a function
>> > linkonce_odr linkage may be neither inline declared nor have
in-class
>> > definition.
>> >
>> > David
>> >
>> >
>> > On Wed, Jun 24, 2015 at 11:53 AM, Robinson, Paul
>> > <Paul_Robinson at playstation.sony.com> wrote:
>> >>
>> >>
>> >>
>> >> > -----Original Message-----
>> >> > From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-
>> bounces at cs.uiuc.edu]
>> >> > On
>> >> > Behalf Of Easwaran Raman
>> >> > Sent: Wednesday, June 24, 2015 9:54 AM
>> >> > To: Xinliang David Li
>> >> > Cc: <llvmdev at cs.uiuc.edu> List
>> >> > Subject: Re: [LLVMdev] Inline hint for methods defined
in-class
>> >> >
>> >> > Ping.
>> >> >
>> >> > On Wed, Jun 17, 2015 at 4:13 PM, Xinliang David Li
>> <davidxl at google.com>
>> >> > wrote:
>> >> > > that looks like a different fix. The case mentioned
by Easwaran is
>> >> > >
>> >> > > class A{
>> >> > >    int foo () { return 1; }
>> >> > >   ...
>> >> > > };
>> >> > >
>> >> > > where 'foo' is not explicitly declared with
'inline' keyword.
>> >> > >
>> >> > > David
>> >> > >
>> >> > > On Wed, Jun 17, 2015 at 4:07 PM, Balaram Makam
>> <bmakam at codeaurora.org>
>> >> > wrote:
>> >> > >> AFAIK, this was fixed in r233817.
>> >>
>> >> That was later reverted.
>> >>
>> >> > >>
>> >> > >> -----Original Message-----
>> >> > >> From: llvmdev-bounces at cs.uiuc.edu
>> >> > >> [mailto:llvmdev-bounces at cs.uiuc.edu]
>> >> > On
>> >> > >> Behalf Of Easwaran Raman
>> >> > >> Sent: Wednesday, June 17, 2015 6:59 PM
>> >> > >> To: llvmdev at cs.uiuc.edu
>> >> > >> Cc: David Li
>> >> > >> Subject: [LLVMdev] Inline hint for methods
defined in-class
>> >> > >>
>> >> > >> Clang adds the InlineHint attribute to functions
that are
>> explicitly
>> >> > marked
>> >> > >> inline, but not if they are defined in the class
body. I tried the
>> >> > following
>> >> > >> patch, which I believe handles the in-class
definition
>> >> > >> case:
>> >> > >>
>> >> > >> --- a/lib/CodeGen/CodeGenFunction.cpp
>> >> > >> +++ b/lib/CodeGen/CodeGenFunction.cpp
>> >> > >> @@ -630,7 +630,7 @@ void
CodeGenFunction::StartFunction(GlobalDecl
>> >> > >> GD,
>> >> > >>    if (const FunctionDecl *FD =
dyn_cast_or_null<FunctionDecl>(D))
>> {
>> >> > >>      if (!CGM.getCodeGenOpts().NoInline) {
>> >> > >>        for (auto RI : FD->redecls())
>> >> > >> -        if (RI->isInlineSpecified()) {
>> >> > >> +        if (RI->isInlined()) {
>> >> > >>           
Fn->addFnAttr(llvm::Attribute::InlineHint);
>> >> > >>            break;
>> >> > >>          }
>> >> > >>
>> >> > >> I tried this on C++ benchmarks in SPEC 2006.
There is no
>> noticeable
>> >> > >> performance difference and the maximum text size
increase is <
>> 0.25%.
>> >> > >> I then built clang with and without this change.
This increases
>> the
>> >> > text
>> >> > >> size by 4.1%.  For measuring performance, I
compiled a large (4.8
>> >> > million
>> >> > >> lines) preprocessed file. This change improves
runtime performance
>> by
>> >> > 0.9%
>> >> > >> (average of 10 runs) in O0 and O2.
>> >> > >>
>> >> > >> I think knowing whether a function is defined
inside a class body
>> is
>> >> > >> a
>> >> > >> useful hint to the inliner. FWIW, GCC's
inliner doesn't
>> differentiate
>> >> > these
>> >> > >> from explicit inline functions. If the above
results doesn't
>> justify
>> >> > this
>> >> > >> change, are there other benchmarks that I should
evaluate? Another
>> >> > >> possibility is to add a separate hint for this
instead of using
>> the
>> >> > existing
>> >> > >> inlinehint to allow for better tuning in the
inliner.
>> >>
>> >> A function with an in-class definition will have linkonce_odr
linkage,
>> >> so it should be possible to identify such functions in the
inliner
>> >> without introducing the inlinehint attribute.
>> >> --paulr
>> >>
>> >> > >>
>> >> > >> Thanks,
>> >> > >> Easwaran
>> >> > >> _______________________________________________
>> >> > >> LLVM Developers mailing list
>> >> > >> LLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.edu
>> >> > >>
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >> > >>
>> >> > _______________________________________________
>> >> > LLVM Developers mailing list
>> >> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >>
>> >> _______________________________________________
>> >> LLVM Developers mailing list
>> >> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >
>> >

Robinson, Paul

2015-Jun-24 21:43 UTC

head link

[LLVMdev] Inline hint for methods defined in-class

> -----Original Message-----
> From: Xinliang David Li [mailto:davidxl at google.com]
> Sent: Wednesday, June 24, 2015 2:17 PM
> To: Robinson, Paul
> Cc: Easwaran Raman; Xinliang David Li; <llvmdev at cs.uiuc.edu> List
> Subject: Re: [LLVMdev] Inline hint for methods defined in-class
> 
> On Wed, Jun 24, 2015 at 2:10 PM, Robinson, Paul
> <Paul_Robinson at playstation.sony.com> wrote:
> >> -----Original Message-----
> >> From: Easwaran Raman [mailto:eraman at google.com]
> >> Sent: Wednesday, June 24, 2015 1:27 PM
> >> To: Xinliang David Li
> >> Cc: Robinson, Paul; Xinliang David Li; <llvmdev at
cs.uiuc.edu> List
> >> Subject: Re: [LLVMdev] Inline hint for methods defined in-class
> >>
> >> The method to identify functions with in-class definitions is one
part
> >> of my question. Even if there is a way to do that without passing
the
> >> hint, I'm interested in getting feedback on treating it at-par
with
> >> functions having the inline hint in inline cost analysis.
> >
> > Well, personally I think having the 'inline' keyword mean
"try harder"
> > is worth something, but that's intuition backed by no data
whatsoever.
> > Your patch would turn 'inline' into noise, when applied to a
function
> > with an in-class definition.  Granted that the way the C++ standard
> > describes 'inline' it is effectively noise in that situation.
> > --paulr
> 
> You are assuming most of the functions are defined in-class, which I
> think is not true.
I'm not assuming any such thing.  Neither my opinion about how I would
prefer the compiler to respond to the 'inline' keyword, nor the simple
fact that the patch turns some uses of the 'inline' keyword into noise,
are in any way related to how often functions are defined in-class.
--paulr

> 
> David
> 
> >
> >>
> >> Thanks,
> >> Easwaran
> >>
> >>
> >> On Wed, Jun 24, 2015 at 12:56 PM, Xinliang David Li
> >> <xinliangli at gmail.com> wrote:
> >> > The problem is that the other way around is not true: a
function
> >> > linkonce_odr linkage may be neither inline declared nor have
in-class
> >> > definition.
> >> >
> >> > David
> >> >
> >> >
> >> > On Wed, Jun 24, 2015 at 11:53 AM, Robinson, Paul
> >> > <Paul_Robinson at playstation.sony.com> wrote:
> >> >>
> >> >>
> >> >>
> >> >> > -----Original Message-----
> >> >> > From: llvmdev-bounces at cs.uiuc.edu
[mailto:llvmdev-
> >> bounces at cs.uiuc.edu]
> >> >> > On
> >> >> > Behalf Of Easwaran Raman
> >> >> > Sent: Wednesday, June 24, 2015 9:54 AM
> >> >> > To: Xinliang David Li
> >> >> > Cc: <llvmdev at cs.uiuc.edu> List
> >> >> > Subject: Re: [LLVMdev] Inline hint for methods
defined in-class
> >> >> >
> >> >> > Ping.
> >> >> >
> >> >> > On Wed, Jun 17, 2015 at 4:13 PM, Xinliang David Li
> >> <davidxl at google.com>
> >> >> > wrote:
> >> >> > > that looks like a different fix. The case
mentioned by Easwaran
> is
> >> >> > >
> >> >> > > class A{
> >> >> > >    int foo () { return 1; }
> >> >> > >   ...
> >> >> > > };
> >> >> > >
> >> >> > > where 'foo' is not explicitly declared
with 'inline' keyword.
> >> >> > >
> >> >> > > David
> >> >> > >
> >> >> > > On Wed, Jun 17, 2015 at 4:07 PM, Balaram Makam
> >> <bmakam at codeaurora.org>
> >> >> > wrote:
> >> >> > >> AFAIK, this was fixed in r233817.
> >> >>
> >> >> That was later reverted.
> >> >>
> >> >> > >>
> >> >> > >> -----Original Message-----
> >> >> > >> From: llvmdev-bounces at cs.uiuc.edu
> >> >> > >> [mailto:llvmdev-bounces at cs.uiuc.edu]
> >> >> > On
> >> >> > >> Behalf Of Easwaran Raman
> >> >> > >> Sent: Wednesday, June 17, 2015 6:59 PM
> >> >> > >> To: llvmdev at cs.uiuc.edu
> >> >> > >> Cc: David Li
> >> >> > >> Subject: [LLVMdev] Inline hint for methods
defined in-class
> >> >> > >>
> >> >> > >> Clang adds the InlineHint attribute to
functions that are
> >> explicitly
> >> >> > marked
> >> >> > >> inline, but not if they are defined in the
class body. I tried
> the
> >> >> > following
> >> >> > >> patch, which I believe handles the in-class
definition
> >> >> > >> case:
> >> >> > >>
> >> >> > >> --- a/lib/CodeGen/CodeGenFunction.cpp
> >> >> > >> +++ b/lib/CodeGen/CodeGenFunction.cpp
> >> >> > >> @@ -630,7 +630,7 @@ void
> CodeGenFunction::StartFunction(GlobalDecl
> >> >> > >> GD,
> >> >> > >>    if (const FunctionDecl *FD >
dyn_cast_or_null<FunctionDecl>(D))
> >> {
> >> >> > >>      if (!CGM.getCodeGenOpts().NoInline) {
> >> >> > >>        for (auto RI : FD->redecls())
> >> >> > >> -        if (RI->isInlineSpecified()) {
> >> >> > >> +        if (RI->isInlined()) {
> >> >> > >>           
Fn->addFnAttr(llvm::Attribute::InlineHint);
> >> >> > >>            break;
> >> >> > >>          }
> >> >> > >>
> >> >> > >> I tried this on C++ benchmarks in SPEC
2006. There is no
> >> noticeable
> >> >> > >> performance difference and the maximum text
size increase is <
> >> 0.25%.
> >> >> > >> I then built clang with and without this
change. This increases
> >> the
> >> >> > text
> >> >> > >> size by 4.1%.  For measuring performance, I
compiled a large
> (4.8
> >> >> > million
> >> >> > >> lines) preprocessed file. This change
improves runtime
> performance
> >> by
> >> >> > 0.9%
> >> >> > >> (average of 10 runs) in O0 and O2.
> >> >> > >>
> >> >> > >> I think knowing whether a function is
defined inside a class
> body
> >> is
> >> >> > >> a
> >> >> > >> useful hint to the inliner. FWIW, GCC's
inliner doesn't
> >> differentiate
> >> >> > these
> >> >> > >> from explicit inline functions. If the
above results doesn't
> >> justify
> >> >> > this
> >> >> > >> change, are there other benchmarks that I
should evaluate?
> Another
> >> >> > >> possibility is to add a separate hint for
this instead of using
> >> the
> >> >> > existing
> >> >> > >> inlinehint to allow for better tuning in
the inliner.
> >> >>
> >> >> A function with an in-class definition will have
linkonce_odr
> linkage,
> >> >> so it should be possible to identify such functions in
the inliner
> >> >> without introducing the inlinehint attribute.
> >> >> --paulr
> >> >>
> >> >> > >>
> >> >> > >> Thanks,
> >> >> > >> Easwaran
> >> >> > >>
_______________________________________________
> >> >> > >> LLVM Developers mailing list
> >> >> > >> LLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.edu
> >> >> > >>
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >> >> > >>
> >> >> > _______________________________________________
> >> >> > LLVM Developers mailing list
> >> >> > LLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.edu
> >> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >> >>
> >> >> _______________________________________________
> >> >> LLVM Developers mailing list
> >> >> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >> >
> >> >

Xinliang David Li

2015-Jun-24 21:49 UTC

head link

[LLVMdev] Inline hint for methods defined in-class

Sorry for misinterpreting, but what is the basis for the simple fact
you mentioned?

David

On Wed, Jun 24, 2015 at 2:43 PM, Robinson, Paul
<Paul_Robinson at playstation.sony.com> wrote:>> -----Original Message-----
>> From: Xinliang David Li [mailto:davidxl at google.com]
>> Sent: Wednesday, June 24, 2015 2:17 PM
>> To: Robinson, Paul
>> Cc: Easwaran Raman; Xinliang David Li; <llvmdev at cs.uiuc.edu>
List
>> Subject: Re: [LLVMdev] Inline hint for methods defined in-class
>>
>> On Wed, Jun 24, 2015 at 2:10 PM, Robinson, Paul
>> <Paul_Robinson at playstation.sony.com> wrote:
>> >> -----Original Message-----
>> >> From: Easwaran Raman [mailto:eraman at google.com]
>> >> Sent: Wednesday, June 24, 2015 1:27 PM
>> >> To: Xinliang David Li
>> >> Cc: Robinson, Paul; Xinliang David Li; <llvmdev at
cs.uiuc.edu> List
>> >> Subject: Re: [LLVMdev] Inline hint for methods defined
in-class
>> >>
>> >> The method to identify functions with in-class definitions is
one part
>> >> of my question. Even if there is a way to do that without
passing the
>> >> hint, I'm interested in getting feedback on treating it
at-par with
>> >> functions having the inline hint in inline cost analysis.
>> >
>> > Well, personally I think having the 'inline' keyword mean
"try harder"
>> > is worth something, but that's intuition backed by no data
whatsoever.
>> > Your patch would turn 'inline' into noise, when applied to
a function
>> > with an in-class definition.  Granted that the way the C++
standard
>> > describes 'inline' it is effectively noise in that
situation.
>> > --paulr
>>
>> You are assuming most of the functions are defined in-class, which I
>> think is not true.
>
> I'm not assuming any such thing.  Neither my opinion about how I would
> prefer the compiler to respond to the 'inline' keyword, nor the
simple
> fact that the patch turns some uses of the 'inline' keyword into
noise,
> are in any way related to how often functions are defined in-class.
> --paulr
>
>
>>
>> David
>>
>> >
>> >>
>> >> Thanks,
>> >> Easwaran
>> >>
>> >>
>> >> On Wed, Jun 24, 2015 at 12:56 PM, Xinliang David Li
>> >> <xinliangli at gmail.com> wrote:
>> >> > The problem is that the other way around is not true: a
function
>> >> > linkonce_odr linkage may be neither inline declared nor
have in-class
>> >> > definition.
>> >> >
>> >> > David
>> >> >
>> >> >
>> >> > On Wed, Jun 24, 2015 at 11:53 AM, Robinson, Paul
>> >> > <Paul_Robinson at playstation.sony.com> wrote:
>> >> >>
>> >> >>
>> >> >>
>> >> >> > -----Original Message-----
>> >> >> > From: llvmdev-bounces at cs.uiuc.edu
[mailto:llvmdev-
>> >> bounces at cs.uiuc.edu]
>> >> >> > On
>> >> >> > Behalf Of Easwaran Raman
>> >> >> > Sent: Wednesday, June 24, 2015 9:54 AM
>> >> >> > To: Xinliang David Li
>> >> >> > Cc: <llvmdev at cs.uiuc.edu> List
>> >> >> > Subject: Re: [LLVMdev] Inline hint for methods
defined in-class
>> >> >> >
>> >> >> > Ping.
>> >> >> >
>> >> >> > On Wed, Jun 17, 2015 at 4:13 PM, Xinliang David
Li
>> >> <davidxl at google.com>
>> >> >> > wrote:
>> >> >> > > that looks like a different fix. The case
mentioned by Easwaran
>> is
>> >> >> > >
>> >> >> > > class A{
>> >> >> > >    int foo () { return 1; }
>> >> >> > >   ...
>> >> >> > > };
>> >> >> > >
>> >> >> > > where 'foo' is not explicitly
declared with 'inline' keyword.
>> >> >> > >
>> >> >> > > David
>> >> >> > >
>> >> >> > > On Wed, Jun 17, 2015 at 4:07 PM, Balaram
Makam
>> >> <bmakam at codeaurora.org>
>> >> >> > wrote:
>> >> >> > >> AFAIK, this was fixed in r233817.
>> >> >>
>> >> >> That was later reverted.
>> >> >>
>> >> >> > >>
>> >> >> > >> -----Original Message-----
>> >> >> > >> From: llvmdev-bounces at cs.uiuc.edu
>> >> >> > >> [mailto:llvmdev-bounces at cs.uiuc.edu]
>> >> >> > On
>> >> >> > >> Behalf Of Easwaran Raman
>> >> >> > >> Sent: Wednesday, June 17, 2015 6:59 PM
>> >> >> > >> To: llvmdev at cs.uiuc.edu
>> >> >> > >> Cc: David Li
>> >> >> > >> Subject: [LLVMdev] Inline hint for
methods defined in-class
>> >> >> > >>
>> >> >> > >> Clang adds the InlineHint attribute to
functions that are
>> >> explicitly
>> >> >> > marked
>> >> >> > >> inline, but not if they are defined in
the class body. I tried
>> the
>> >> >> > following
>> >> >> > >> patch, which I believe handles the
in-class definition
>> >> >> > >> case:
>> >> >> > >>
>> >> >> > >> --- a/lib/CodeGen/CodeGenFunction.cpp
>> >> >> > >> +++ b/lib/CodeGen/CodeGenFunction.cpp
>> >> >> > >> @@ -630,7 +630,7 @@ void
>> CodeGenFunction::StartFunction(GlobalDecl
>> >> >> > >> GD,
>> >> >> > >>    if (const FunctionDecl *FD >>
dyn_cast_or_null<FunctionDecl>(D))
>> >> {
>> >> >> > >>      if
(!CGM.getCodeGenOpts().NoInline) {
>> >> >> > >>        for (auto RI : FD->redecls())
>> >> >> > >> -        if
(RI->isInlineSpecified()) {
>> >> >> > >> +        if (RI->isInlined()) {
>> >> >> > >>           
Fn->addFnAttr(llvm::Attribute::InlineHint);
>> >> >> > >>            break;
>> >> >> > >>          }
>> >> >> > >>
>> >> >> > >> I tried this on C++ benchmarks in SPEC
2006. There is no
>> >> noticeable
>> >> >> > >> performance difference and the maximum
text size increase is <
>> >> 0.25%.
>> >> >> > >> I then built clang with and without
this change. This increases
>> >> the
>> >> >> > text
>> >> >> > >> size by 4.1%.  For measuring
performance, I compiled a large
>> (4.8
>> >> >> > million
>> >> >> > >> lines) preprocessed file. This change
improves runtime
>> performance
>> >> by
>> >> >> > 0.9%
>> >> >> > >> (average of 10 runs) in O0 and O2.
>> >> >> > >>
>> >> >> > >> I think knowing whether a function is
defined inside a class
>> body
>> >> is
>> >> >> > >> a
>> >> >> > >> useful hint to the inliner. FWIW,
GCC's inliner doesn't
>> >> differentiate
>> >> >> > these
>> >> >> > >> from explicit inline functions. If the
above results doesn't
>> >> justify
>> >> >> > this
>> >> >> > >> change, are there other benchmarks that
I should evaluate?
>> Another
>> >> >> > >> possibility is to add a separate hint
for this instead of using
>> >> the
>> >> >> > existing
>> >> >> > >> inlinehint to allow for better tuning
in the inliner.
>> >> >>
>> >> >> A function with an in-class definition will have
linkonce_odr
>> linkage,
>> >> >> so it should be possible to identify such functions
in the inliner
>> >> >> without introducing the inlinehint attribute.
>> >> >> --paulr
>> >> >>
>> >> >> > >>
>> >> >> > >> Thanks,
>> >> >> > >> Easwaran
>> >> >> > >>
_______________________________________________
>> >> >> > >> LLVM Developers mailing list
>> >> >> > >> LLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.edu
>> >> >> > >>
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >> >> > >>
>> >> >> > _______________________________________________
>> >> >> > LLVM Developers mailing list
>> >> >> > LLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.edu
>> >> >> >
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >> >>
>> >> >> _______________________________________________
>> >> >> LLVM Developers mailing list
>> >> >> LLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.edu
>> >> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >> >
>> >> >

llvm dev - Jun 2015 - [LLVMdev] Inline hint for methods defined in-class

[LLVMdev] Inline hint for methods defined in-class

[LLVMdev] Inline hint for methods defined in-class

[LLVMdev] Inline hint for methods defined in-class