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RISC-V: allow building scalable RVV support with GCC, LLVM 16 support#23383

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Apr 10, 2023
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RISC-V: allow building scalable RVV support with GCC, LLVM 16 support#23383
opencv-pushbot merged 1 commit intoopencv:4.xfrom
mshabunin:rvv-scalable-gcc

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@mshabunin mshabunin commented Mar 21, 2023 •
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Related issue #22608

  • GCC does not support "overloaded RVV intrinsics", but we can add some of them in our code
  • LLVM since version 16 uses __riscv_<name> naming scheme (see related ticket), so we need to add compatibility headers to rename our 0.10 intinsics to the new scheme (also for some "overloaded intrinsics")

TODO:

  • check and fix compilation with GCC still does not work due to toolchain issue or limitation
  • extract overloaded intsinsics implementation to separate header
  • macros for overloaded intrinsics looks too broad, maybe convert them to function macros / inline functions / undef? used headers from RISC-V collab as is
  • clean-up the code - reduce modifications

Note: scalable RVV compilation using GCC still does not work (T-Head 2.6.1 and RISC-V Collab Toolchain@rvv_next) due to compiler issues or limitations. More analysis needed.

force_builders=Custom
build_image:Custom=riscv-clang-rvv
Xbuild_image:Custom=riscv-clang-rvv-128
Xbuild_image:Custom=riscv-gcc-rvv-07
test_modules:Custom=core,imgproc,dnn
buildworker:Custom=linux-4
test_timeout:Custom=600
build_contrib:Custom=OFF

@mshabunin mshabunin mentioned this pull request Mar 21, 2023
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@mshabunin mshabunin marked this pull request as ready for review April 5, 2023 11:19
@opencv-alalek opencv-alalek added this to the 4.8.0 milestone Apr 6, 2023
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opencv-alalek approved these changes Apr 6, 2023
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LGTM 👍

@opencv-alalek opencv-alalek self-assigned this Apr 6, 2023
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zhongjuzhe commented Apr 10, 2023

Can you use upstream GCC (GCC 13.0) test? We don't maintain rvv-next any more. All update upstream GCC directely.
https://github.com/gcc-mirror/gcc

@opencv-pushbot opencv-pushbot merged commit daf9de7 into opencv:4.x Apr 10, 2023
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opencv-alalek commented Apr 12, 2023

@zhongjuzhe Thank you for the information!
Is there some example how to build RISC-V GCC toolchain from upstream source code? (similar to https://github.com/riscv-collab/riscv-gnu-toolchain instructions)
CI logs? Or Dockerfile?

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zhongjuzhe commented Apr 12, 2023

It seems that RISC-V toolchain doesn't bump to latest upstream GCC. I think you can file an issue to @kito-cheng and ask him to update the toolchain.

Here is an simple example to verify that both GCC and LLVM are consisten each other with the same API doc:
https://godbolt.org/z/dz83ozbeb

compiler explorer has showed that both GCC and LLVM are recognizing same API RVV.

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mshabunin commented Apr 17, 2023

I've been able to build riscv-collab toolchain with the latest GCC by updating gcc submodule to master manually. It can build OpenCV with scalable RVV support, but failed to build non-scalable (intrin_rvv.hpp) variant. I'm going to take a closer look. @zhongjuzhe , thank you for guidance!

@mshabunin mshabunin deleted the rvv-scalable-gcc branch April 17, 2023 10:21
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zhongjuzhe commented Apr 17, 2023 via email

@asmorkalov asmorkalov mentioned this pull request May 31, 2023
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