tra added inline comments.
================
Comment at: lib/Driver/Tools.cpp:10707
@@ +10706,3 @@
+ // ptxas does not accept -g option if optimization is enabled, so we ignore
+ // compiler's -O* options if we want debug info.
+ CmdArgs.push_back("-g");
----------------
hfinkel wrote:
> echristo wrote:
> > tra wrote:
> > > echristo wrote:
> > > > tra wrote:
> > > > > hfinkel wrote:
> > > > > > echristo wrote:
> > > > > > > jlebar wrote:
> > > > > > > > I think this is would be very surprising to users. -g does not
> > > > > > > > usually have a large performance impact, so -O2 -g does not
> > > > > > > > generally mean "generate slow code," as far as I know. I'm
> > > > > > > > concerned that this will result in people accidentally
> > > > > > > > compiling with ptxas -O0 (which is why I didn't do it like this
> > > > > > > > to begin with).
> > > > > > > >
> > > > > > > > Can we accomplish this in a more explicit way?
> > > > > > > Other than warning I'm not sure what we can do, we could do that
> > > > > > > instead and make everyone use O0 that wants debug info in their
> > > > > > > ptx?
> > > > > > I'd rather we refuse to do anything (i.e. produce an error) than
> > > > > > silently remove either optimizations or -g. Do we have a way to
> > > > > > separately specify the optimization level for host and device code?
> > > > > > If not, looks like we should add one.
> > > > > NVCC has -G option to control ptxas' debug options. If it's present,
> > > > > ptxas optimizations are disabled. I could add a similar option.
> > > > > "-gcuda-device" perhaps?
> > > > >
> > > > We can do that, I'd have warned because it doesn't seem like something
> > > > we should hard error on, but I can see that perspective, i.e. we asked
> > > > for "incompatible" options.
> > > >
> > > > And no, we don't currently have a way to do that. We can try to come up
> > > > with a driver interface.
> > > @hfinkel: separate option should work. Any suggestions for a good name?
> > > -gcuda-device sounds awkward.
> > >
> > > @echristo: "-O0" is not going to work for everyone in practice due to
> > > ptxas limitations. For instance on some thrust files ptxas runs out of
> > > memory on all non-inlined functions in unoptimized code. Compiling with
> > > -O2 is one way to work around that, but I do want device-side debug info!
> > >
> > Huh? I'm not sure what you're doing here then with turning off
> > optimizations in the presence of debug info requests. Your commentary made
> > it sound like you can't have both.
> > @hfinkel: separate option should work. Any suggestions for a good name?
> > -gcuda-device sounds awkward.
>
> I agree it sounds awkward, but I currently have no better suggestion.
@echristo: I assumed you were talking about compiler when you said "make
everyone use O0". I need compiler to optimize code with -O2, but run ptxas with
-g and -O0 which this patch makes possible.
I'll update the patch to add an option to control device-side debug info
explicitly.
http://reviews.llvm.org/D17111
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
