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Arm64/Sve: Enable Sve only if vector length is 128 #104174

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merged 4 commits into from
Jun 28, 2024
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Arm64/Sve: Enable Sve only if vector length is 128 #104174

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952a3a6
Enable InstructionSet_Sve only if system VL == 128
kunalspathak Jun 28, 2024
6117546
Update src/coreclr/vm/codeman.cpp
kunalspathak Jun 28, 2024
3d8b63a
Update src/coreclr/vm/codeman.cpp
jkotas Jun 28, 2024
7cf376c
Remove hardcoding of 128 for windows
kunalspathak Jun 28, 2024
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6 changes: 4 additions & 2 deletions src/coreclr/vm/codeman.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1514,8 +1514,10 @@ void EEJitManager::SetCpuInfo()
uint32_t maxVectorTLength = (maxVectorTBitWidth / 8);
uint64_t sveLengthFromOS = GetSveLengthFromOS();
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This method to be adjusted to return 0 on Windows with this change as otherwise we could be in an unsupported state since it's currently hardcoded as:

;; uint64_t GetSveLengthFromOS(void);
    LEAF_ENTRY GetSveLengthFromOS
        ;; TODO-SVE: Remove the hardcoded value 128 and uncomment once CI machines are updated to use MASM 14.4 or later
        ;; rdvl    x0, 1
        mov     x0, #128
        ret     lr
    LEAF_END

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hhm, so this is the case where if windows is running on 256-bit machine, we shouldn't be returning 128-bits because that will falsely turn on SVE. Let me uncomment the right way to do it to see if helix machines got the assembler upgraded to understand rdvl.

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alright, so that seemed to be working now.


// Do not enable SVE when the user specified vector length is smaller than the one offered by underlying OS.
if ((maxVectorTLength >= sveLengthFromOS) || (maxVectorTBitWidth == 0))
// For now, enable SVE only when the system vector length is 128-bits
// TODO: https://github.com/dotnet/runtime/issues/101477
if (sveLengthFromOS == 128)
// if ((maxVectorTLength >= sveLengthFromOS) || (maxVectorTBitWidth == 0))
{
CPUCompileFlags.Set(InstructionSet_Sve);
}
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