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[FMV][AArch64] Release notes for LLVM20. #125525

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Feb 6, 2025
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[FMV][AArch64] Release notes for LLVM20. #125525

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7 changes: 7 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -654,6 +654,10 @@ Attribute Changes in Clang

- The ``target_version`` attribute is now only supported for AArch64 and RISC-V architectures.

- When targeting AArch64, a function declaration annotated with ``target_version("default")``
now generates a mangled default version of the function, whereas before at least one more
version other than the default was required to trigger Function Multi Versioning.

- Clang now permits the usage of the placement new operator in ``[[msvc::constexpr]]``
context outside of the std namespace. (#GH74924)

Expand Down Expand Up @@ -1188,6 +1192,9 @@ Arm and AArch64 Support

* FUJITSU-MONAKA (fujitsu-monaka)

- Runtime detection of depended-on Function Multi Versioning features has been added
in accordance with the Arm C Language Extensions (ACLE).

Android Support
^^^^^^^^^^^^^^^

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14 changes: 14 additions & 0 deletions llvm/docs/ReleaseNotes.md
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Expand Up @@ -130,6 +130,10 @@ Changes to building LLVM
Changes to TableGen
-------------------

* The ARMTargetDefEmitter now binds Funtion Multi Versioning features to the
corresponding AArch64 Architecture Extensions such that their dependencies
can be autogenerated using TableGen.

Changes to Interprocedural Optimizations
----------------------------------------

Expand Down Expand Up @@ -431,9 +435,19 @@ Changes to the C API
Changes to the CodeGen infrastructure
-------------------------------------

* GlobalOpt can now statically resolve calls to multi-versioned functions when targeting AArch64.
These calls would otherwise be routed through an IFunc resolver function. This optimization
can be applied when the caller is either a multi-versioned function itself, or it is compiled
with a sufficiently high set of architecture features (including the `target` attribute, and
command line options).

Changes to the Metadata Info
---------------------------------

* Multi-versioned functions targeting AArch64 are annotated with new metadata named `fmv-features`.
The metadata string value consists of a comma-separated list of Function Multi Versioning feature
names as defined in the Arm C Language Extensions (ACLE).

Changes to the Debug Info
---------------------------------

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