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[clang][SYCL] Disable float128 device mode diagnostic #128513

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Merged
ldrumm merged 1 commit into from
Mar 12, 2025
Merged

[clang][SYCL] Disable float128 device mode diagnostic #128513

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3 changes: 2 additions & 1 deletion clang/lib/Sema/SemaDeclAttr.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4700,7 +4700,8 @@ void Sema::AddModeAttr(Decl *D, const AttributeCommonInfo &CI,

if (NewElemTy.isNull()) {
// Only emit diagnostic on host for 128-bit mode attribute
if (!(DestWidth == 128 && getLangOpts().CUDAIsDevice))
if (!(DestWidth == 128 &&
(getLangOpts().CUDAIsDevice || getLangOpts().SYCLIsDevice)))
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@npmiller npmiller Feb 24, 2025

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Side-note CUDAIsDevice || SYCLIsDevice seems like a pretty common pattern and I believe HIP also uses CUDAIsDevice, it could be good to refactor in the future this to have a common "device compilation" option if possible.

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@bader bader Mar 4, 2025

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On that note: I think the same problem can be reproduced by OpenMP offload as well, so we might need to extend the condition with || (getLangOpts().OpenMP && getLangOpts().OpenMPIsTargetDevice).

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@npmiller npmiller Mar 12, 2025

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I'll try to reproduce this with OpenMP and open a follow up PR if it has the same issue

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@npmiller npmiller Mar 13, 2025

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Not sure exactly how it works for OpenMP, but it doesn't seem to be affected, with a float128.cpp file just containing:

typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));

And testing without this patch:

With SYCL:

$ ./bin/clang++ float128.cpp -fsycl -fsycl-targets=nvptx64-nvidia-cuda -Xclang -fsycl-is-device -fsyntax-only -o o
float128.cpp:1:52: error: unsupported machine mode '__TC__'
   1 | typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));
     |                                                    ^
1 error generated.
$

With OpenMP:

$ ./bin/clang++ ../build/float128.cpp -fopenmp -fopenmp-targets=nvptx64-nvidia-cuda -Xclang -fopenmp-is-target-device -fsyntax-only -o o
$

And same thing without specifying an OpenMP target.

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@bader bader Mar 13, 2025

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Now, I'd like to understand how OpenMP compiler solves that problem and why OpenMP solution seems to be different from CUDA. @npmiller, do you know any reason why they should be different?

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@npmiller npmiller Mar 13, 2025

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No I'm not very familiar with this part of the compiler, and even less with OpenMP.

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@jdoerfert jdoerfert Jan 29, 2026

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FWIW, now that OpenMP has SPIRV support, this popped up on my machine.

llvm-project/build main ✗ cat test.cpp
typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));

llvm-project/build main ❯ ./bin/clang++ test.cpp -fopenmp -fopenmp-targets=spirv64 -Xclang -fopenmp-is-target-device -fsyntax-only -o o  --libomptarget-spirv-bc-path=./lib/spirv64-intel/
In file included from <built-in>:1:
In file included from /home/jdoerfert/dev/llvm-project/build/lib/clang/23/include/openmp_wrappers/__clang_openmp_device_functions.h:67:
In file included from /usr/lib64/gcc/x86_64-pc-linux-gnu/15.2.1/../../../../include/c++/15.2.1/cstdlib:83:
In file included from /home/jdoerfert/dev/llvm-project/build/lib/clang/23/include/llvm_libc_wrappers/stdlib.h:16:
In file included from /usr/include/stdlib.h:56:
/usr/include/bits/floatn.h:83:52: error: unsupported machine mode '__TC__'
   83 | typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));
      |                                                    ^
test.cpp:1:52: error: unsupported machine mode '__TC__'
    1 | typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));
      |                                                    ^
2 errors generated.

The suggested fix works for me. Could you make a PR?

Diag(AttrLoc, diag::err_machine_mode) << 1 /*Unsupported*/ << Name;
return;
}
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1 change: 1 addition & 0 deletions clang/test/SemaSYCL/float128.cpp
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
// RUN: %clang_cc1 -triple spir64 -fsycl-is-device -verify -fsyntax-only %s
// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsycl-is-device -fsyntax-only %s

typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));
typedef __float128 BIGTY;

template <class T>
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