gtbercea added inline comments.
================
Comment at: lib/Driver/ToolChains/Cuda.cpp:170-182
- // This code prevents IsValid from being set when
- // no libdevice has been found.
- bool allEmpty = true;
- std::string LibDeviceFile;
- for (auto key : LibDeviceMap.keys()) {
- LibDeviceFile = LibDeviceMap.lookup(key);
- if (!LibDeviceFile.empty())
----------------
tra wrote:
> tra wrote:
> > gtbercea wrote:
> > > gtbercea wrote:
> > > > Hahnfeld wrote:
> > > > > tra wrote:
> > > > > > Hahnfeld wrote:
> > > > > > > tra wrote:
> > > > > > > > I'd keep this code. It appears to serve useful purpose as it
> > > > > > > > requires CUDA installation to have at least some libdevice
> > > > > > > > library in it. It gives us a change to find a valid
> > > > > > > > installation, instead of ailing some time later when we ask for
> > > > > > > > a libdevice file and fail because there are none.
> > > > > > > We had some internal discussions about this after I submitted the
> > > > > > > patch here.
> > > > > > >
> > > > > > > The main question is: Do we want to support CUDA installations
> > > > > > > without libdevice and are there use cases for that? I'd say that
> > > > > > > the user should be able to use a toolchain without libdevice
> > > > > > > together with `-nocudalib`.
> > > > > > Sounds reasonable. How about keeping the code but putting it under
> > > > > > `if(!hasArg(nocudalib))`?
> > > > > >
> > > > > Ok, I'll do that in a separate patch and keep the code here for now.
> > > > The problem with nocudalib is that if for example you write a test,
> > > > which looks to verify some device facing feature that requires a
> > > > libdevice to be found (so you don't want to use nocudalib), it will
> > > > probably work on your machine which has the correct CUDA setup but fail
> > > > on another machine which does not (which is where you want to use
> > > > nocudalib). You can see the contradiction there.
> > > Just to be clear I am arguing for keeping this code :)
> > @gtbercea: I'm not sure I follow your example. If you're talking about
> > clang tests, we do have fake CUDA installation setup under
> > test/Driver/Inputs which removes dependency on whatever CUDA you may or may
> > not have installed on your machine. I also don't see a contradiction -- you
> > you do need libdevice, it makes no point picking a broken CUDA installation
> > which does not have any libdevice files. If you explicitly tell compiler
> > that you don't need libdevice, that would make CUDA w/o libdevice
> > acceptable. With --cuda-path you do have a way to tell clang which
> > installation you want it to use. What do I miss?
> >
> >
> Ah, you were arguing with Hahnfeld@'s -nocudalib example. Then I guess we're
> in violent agreement.
I fully agree with this: "you do need libdevice, it makes no point picking a
broken CUDA installation which does not have any libdevice files. If you
explicitly tell compiler that you don't need libdevice, that would make CUDA
w/o libdevice acceptable."
I was trying to show an example of a situation where you have your code
compiled using nocudalib on one machine and then the same code will error on a
machine which requires the nocudalib flag to be passed to make up for the
absence of libdevice.
https://reviews.llvm.org/D38883
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