[PATCH] D47895: llvm: Add support for "-fno-delete-null-pointer-checks"

[Sanjoy Das via Phabricator via llvm-commits]

sanjoy added a comment.

Drive by comments

You also need to change the inliner to not inline `null-pointer-is-dereferenceable` into functions that don't have that attribute.



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Comment at: docs/LangRef.rst:1464
     as SEH, will still provide their implementation defined semantics.
+``"null-pointer-is-defined"``
+   If ``"null-pointer-is-defined"`` is set to ``"true"``, then ``null`` address
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This should be called `null-pointer-is-dereferenceable` or something like that.


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Comment at: docs/LangRef.rst:1466
+   If ``"null-pointer-is-defined"`` is set to ``"true"``, then ``null`` address
+   is considered to be a valid address for memory accesses. Any analysis or
+   optimization should not treat dereferencing a pointer to ``null`` as
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Might be worth clarifying if this is just loads or both loads and stores.


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Comment at: docs/LangRef.rst:1468
+   optimization should not treat dereferencing a pointer to ``null`` as
+   ``undefined`` behavior in this function.
 ``optforfuzzing``
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efriedma wrote:
> undefined isn't a keyword.
What about functions called from this function?


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Comment at: lib/Transforms/Utils/Local.cpp:1813
         Value *Callee = CI->getCalledValue();
-        if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
+        if ((isa<ConstantPointerNull>(Callee) &&
+             !NullPointerIsDefined(CI->getFunction())) ||
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I don't think we can fold calls to `undef` either -- the only reason why we can normally do this is because `Callee` could be `null`.


Repository:
  rL LLVM

https://reviews.llvm.org/D47895