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ReleaseNotes: Add updates in LangRef related with undef/poison

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Juneyoung Lee 2020-09-08 11:40:24 +09:00
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@ -101,6 +101,18 @@ Changes to the LLVM IR
where ``uint64_t`` was used to denote the size in bits of a IR type
we have partially migrated the codebase to using ``llvm::TypeSize``.
* Branching on ``undef``/``poison`` is undefined behavior. It is needed for
correctly analyzing value ranges based on branch conditions. This is
consistent with MSan's behavior as well.
* ``memset``/``memcpy``/``memmove`` can take ``undef``/``poison`` pointer(s)
if the size to fill is zero.
* Passing ``undef``/``poison`` to a standard I/O library function call
(`printf`/`fputc`/...) is undefined behavior. The new ``noundef`` attribute
is attached to the functions' arguments. The full list is available at
``llvm::inferLibFuncAttributes``.
Changes to building LLVM
------------------------
@ -305,6 +317,10 @@ Changes to the Go bindings
Changes to the DAG infrastructure
---------------------------------
* A SelDag-level freeze instruction has landed. It is simply lowered as a copy
operation to MachineIR, but to make it fully correct either IMPLICIT_DEF
should be fixed or the equivalent FREEZE operation should be added to
MachineIR.
Changes to the Debug Info
---------------------------------