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[LLVM][LangRef] Restrict vscale to be a signed power-of-two integer. #183080

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paulwalker-arm merged 2 commits into from
Feb 24, 2026
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[LLVM][LangRef] Restrict vscale to be a signed power-of-two integer. #183080

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fbb3e47
[LLVM][LangRef] Restrict vscale to be a signed power-of-two integer.
paulwalker-arm Feb 24, 2026
284f6af
Update MLIR documentation for vscale.
paulwalker-arm Feb 24, 2026
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10 changes: 5 additions & 5 deletions llvm/docs/LangRef.rst
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Expand Up @@ -4678,9 +4678,9 @@ elementtype may be any integer, floating-point, pointer type, or a sized
target extension type that has the ``CanBeVectorElement`` property. Vectors
of size zero are not allowed. For scalable vectors, the total number of
elements is a constant multiple (called vscale) of the specified number
of elements; vscale is a positive integer that is unknown at compile time
and the same hardware-dependent constant for all scalable vectors at run
time. The size of a specific scalable vector type is thus constant within
of elements; vscale is a positive power-of-two integer that is unknown at
compile time and the same hardware-dependent constant for all scalable vectors
at run time. The size of a specific scalable vector type is thus constant within
IR, even if the exact size in bytes cannot be determined until run time.

:Examples:
Expand Down Expand Up @@ -31501,8 +31501,8 @@ vectors such as ``<vscale x 16 x i8>``.
Semantics:
""""""""""

``vscale`` is a positive value that is constant throughout program
execution, but is unknown at compile time.
``vscale`` is a positive power-of-two integer that is constant throughout
program execution, but is unknown at compile time.
If the result value does not fit in the result type, then the result is
a :ref:`poison value <poisonvalues>`.

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9 changes: 5 additions & 4 deletions mlir/docs/Dialects/Vector.md
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Expand Up @@ -97,10 +97,11 @@ Finally, MLIR takes the same view on scalable Vectors as LLVM (c.f.
[VectorType](https://llvm.org/docs/LangRef.html#vector-type)):
> For scalable vectors, the total number of elements is a constant multiple
> (called vscale) of the specified number of elements; vscale is a positive
> integer that is unknown at compile time and the same hardware-dependent
> constant for all scalable vectors at run time. The size of a specific
> scalable vector type is thus constant within IR, even if the exact size in
> bytes cannot be determined until run time.
> power-of-two integer that is unknown at compile time and the same
> hardware-dependent constant for all scalable vectors at run time.
> The size of a specific scalable vector type is thus constant within
> IR, even if the exact size in bytes cannot be determined until run
> time.

### Hardware Vector Ops

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