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| author | Nikita Popov <npopov@redhat.com> | 2023-02-01 11:18:47 +0100 |
|---|---|---|
| committer | Nikita Popov <npopov@redhat.com> | 2023-02-14 08:23:37 +0100 |
| commit | 2e9549db268645accb83ebf031fbb1de84b00ca9 (patch) | |
| tree | 90329fe3747e20ee2439ca92c66bde719ff61cca | |
| parent | af838c1b1c20c7b3b970e81039a1992857fe76bb (diff) | |
| download | llvm-2e9549db268645accb83ebf031fbb1de84b00ca9.zip llvm-2e9549db268645accb83ebf031fbb1de84b00ca9.tar.gz llvm-2e9549db268645accb83ebf031fbb1de84b00ca9.tar.bz2 | |
[LangRef] Global variable declarations imply minimum size
Adjust the wording added in D78952 to say that global variable
declarations (and interposable definitions) do imply a minimum
size (and alignment) on the global. They just don't imply a
maximum size.
We rely on these semantics in at least two places:
* Global dereferenceability: https://github.com/llvm/llvm-project/blob/2153544865a9733b06579823814c981f735e4201/llvm/lib/IR/Value.cpp#L907
* Global inbounds GEP: https://github.com/llvm/llvm-project/blob/2153544865a9733b06579823814c981f735e4201/llvm/lib/IR/ConstantFold.cpp#L2283
Differential Revision: https://reviews.llvm.org/D143057
| -rw-r--r-- | llvm/docs/LangRef.rst | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index 16e2029..cd51a42 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -721,12 +721,11 @@ limits the alignment to the given value. Optimizers are not allowed to impose a stronger alignment on these variables. The maximum alignment is ``1 << 32``. -For global variables declarations, as well as definitions that may be +For global variable declarations, as well as definitions that may be replaced at link time (``linkonce``, ``weak``, ``extern_weak`` and ``common`` -linkage types), LLVM makes no assumptions about the allocation size of the -variables, except that they may not overlap. The alignment of a global variable -declaration or replaceable definition must not be greater than the alignment of -the definition it resolves to. +linkage types), the allocation size and alignment of the definition it resolves +to must be greater than or equal to that of the declaration or replaceable +definition, otherwise the behavior is undefined. Globals can also have a :ref:`DLL storage class <dllstorageclass>`, an optional :ref:`runtime preemption specifier <runtime_preemption_model>`, |