echristo 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");
----------------
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.
================
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");
----------------
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.
http://reviews.llvm.org/D17111
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