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[LangRef] make consequences of NaN rules for pow(i) more explicit #170177

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nikic merged 1 commit into from
Dec 10, 2025
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[LangRef] make consequences of NaN rules for pow(i) more explicit #170177

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14 changes: 14 additions & 0 deletions llvm/docs/LangRef.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -16269,6 +16269,13 @@ Semantics:
This function returns the first value raised to the second power with an
unspecified sequence of rounding operations.

Note that the `powi` function is unusual in that NaN inputs can lead to non-NaN
results, and this depends on the kind of NaN (quiet vs signaling). Due to how
:ref:`LLVM treats NaN values <floatnan>` in non-constrained functions, the
function may non-deterministically treat signaling NaNs as quiet NaNs. For
example, `powi(QNaN, 0)` returns `1.0`, and `powi(SNaN, 0)` may
non-deterministically return `1.0` or a NaN.

.. _t_llvm_sin:

'``llvm.sin.*``' Intrinsic
Expand Down Expand Up @@ -16831,6 +16838,13 @@ trapping or setting ``errno``.
When specified with the fast-math-flag 'afn', the result may be approximated
using a less accurate calculation.

Note that the `pow` function is unusual in that NaN inputs can lead to non-NaN
results, and this depends on the kind of NaN (quiet vs signaling). Due to how
:ref:`LLVM treats NaN values <floatnan>` in non-constrained functions, the
function may non-deterministically treat signaling NaNs as quiet NaNs. For
example, `pow(QNaN, 0.0)` returns `1.0`, and `pow(SNaN, 0.0)` may
non-deterministically return `1.0` or a NaN.

.. _int_exp:

'``llvm.exp.*``' Intrinsic
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