jdenny added inline comments.
================
Comment at: clang/lib/Sema/SemaOpenMP.cpp:1594
+ !Context.getTargetInfo().hasFloat128Type() &&
+ Context.getTargetInfo().getLongDoubleWidth() != 128) ||
(Ty->isIntegerType() && Context.getTypeSize(Ty) == 128 &&
----------------
ABataev wrote:
> jdenny wrote:
> > ABataev wrote:
> > > jdenny wrote:
> > > > ABataev wrote:
> > > > > jdenny wrote:
> > > > > > ABataev wrote:
> > > > > > > jdenny wrote:
> > > > > > > > ABataev wrote:
> > > > > > > > > Hmm, this look strange, at least. Seems to me, in this case
> > > > > > > > > the size of the long double is 128 bit (copied from the
> > > > > > > > > host), but device reports that it does not support 128 bit
> > > > > > > > > double. Seems to me, it is a problem with the device
> > > > > > > > > configuration. Why does the host translate long double to 128
> > > > > > > > > bit fp, while the device translates it to 64 bit FP?
> > > > > > > > Sorry, I think I've misunderstood what's happening here, and my
> > > > > > > > fix is probably wrong.
> > > > > > > >
> > > > > > > > For x86_64, the example from my patch summary fails as
> > > > > > > > described there. Does that work for you?
> > > > > > > >
> > > > > > > > For powerpc64le, the reproducer I added to the test suite fails
> > > > > > > > without this patch. Shouldn't it succeed?
> > > > > > > Still, seems to me like the problem with the device config, not
> > > > > > > the original check.
> > > > > > > Still, seems to me like the problem with the device config, not
> > > > > > > the original check.
> > > > > >
> > > > > > I'm not sure where to begin looking for that. Can you point me in
> > > > > > the right direction? Thanks.
> > > > > You need to understand why host and device report different size of
> > > > > the type. Check how the device is configured in lib/Basic/Targets
> > > > Thanks for the pointer. I think I understand things a bit better now.
> > > >
> > > > Without this patch's fix, the x86_64 example from this patch's summary
> > > > fails while this patch's new x86_64 test case passes. The difference
> > > > is the summary's example doesn't specify `-unknown-linux` after
> > > > `x86_64`, and that's what sets `hasFloat128Type()` to true.
> > > >
> > > > `powerpc64le-unknown-linux-gnu` does not have `__float128`, it seems.
> > > > That's why this patch's new powerpc64le test case fails without this
> > > > patch's fix.
> > > >
> > > > It seems strange to me that the code we're commenting on originally
> > > > looks for the source type to be either `__float128` or 128-bit `long
> > > > double`, and it then requires the target to support `__float128`. It
> > > > doesn't accept 128-bit `long double` support as sufficient. My
> > > > intention in this patch was to extend it to accept either so that all
> > > > the examples above compile. Is that too lenient? Am I misinterpreting
> > > > what's happening?
> > > >
> > > > As for your comment about 64-bit floating point in the device
> > > > translation, I haven't seen that yet. Did I miss it?
> > > The intention of the original patch is to make host and device to have
> > > the same float128 and long double types. Device inherits those types from
> > > the host to be compatible during offloading and to correctly mangle
> > > functions.
> > > Without this we just can't generate offloading regions correctly. If the
> > > host has 128 bit long double, the device also must have 128 bit long
> > > double.
> > > If device does not support 128bit floats, in this case device can only
> > > move the data (do load/stores ops only) and cannot do anything else.
> > Are you intentionally requiring support for `__float128` when the source
> > type is 128-bit `long double`? That seems to mean powerpc64le cannot
> > offload to itself.
> No, if the host has 128 bit long double, the device must also have 128 bit
> long double. It has nothing to do with the float128 type itself.
What if we change the logic to the following?
```
(Ty->isFloat128Type() && !Context.getTargetInfo().hasFloat128Type()) ||
(!Ty->isFloat128Type() && Ty->isRealFloatingType() &&
Context.getTypeSize(Ty) == 128 &&
Context.getTargetInfo().getLongDoubleWidth() != 128)
```
Maybe there's a more succinct way to check if `Ty` is `long double`....
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D64289/new/
https://reviews.llvm.org/D64289
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