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Explicitly state the behavior of inbounds with a null pointer.
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Authored by efriedma on Dec 21 2016, 11:55 AM.

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Reviewers

sanjoy
hfinkel
rsmith

Commits

rG13f2e353110c: Explicitly state the behavior of inbounds with a null pointer.
rL295916: Explicitly state the behavior of inbounds with a null pointer.

Summary

See https://llvm.org/bugs/show_bug.cgi?id=31439; this reflects LLVM's behavior in practice, and should be compatible with C/C++ rules.

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Repository: rL LLVM

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efriedma updated this revision to Diff 82252.Dec 21 2016, 11:55 AM

efriedma retitled this revision from to Explicitly state the behavior of inbounds with a null pointer..

efriedma updated this object.

efriedma added reviewers: rsmith, hfinkel.

efriedma set the repository for this revision to rL LLVM.

efriedma added subscribers: llvm-commits, evstupac, dblaikie.

davide added a subscriber: davide.Dec 21 2016, 12:02 PM

Ping.

LGTM!

This revision is now accepted and ready to land.Feb 18 2017, 11:58 PM

Closed by commit rL295916: Explicitly state the behavior of inbounds with a null pointer. (authored by efriedma). · Explain WhyFeb 22 2017, 5:00 PM

This revision was automatically updated to reflect the committed changes.

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llvm/

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docs/

LangRef.rst

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Diff 89445

llvm/trunk/docs/LangRef.rst

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	If the ``inbounds`` keyword is present, the result value of the			If the ``inbounds`` keyword is present, the result value of the
	``getelementptr`` is a :ref:`poison value <poisonvalues>` if the base			``getelementptr`` is a :ref:`poison value <poisonvalues>` if the base
	pointer is not an in bounds address of an allocated object, or if any			pointer is not an in bounds address of an allocated object, or if any
	of the addresses that would be formed by successive addition of the			of the addresses that would be formed by successive addition of the
	offsets implied by the indices to the base address with infinitely			offsets implied by the indices to the base address with infinitely
	precise signed arithmetic are not an in bounds address of that			precise signed arithmetic are not an in bounds address of that
	allocated object. The in bounds addresses for an allocated object are			allocated object. The in bounds addresses for an allocated object are
	all the addresses that point into the object, plus the address one byte			all the addresses that point into the object, plus the address one byte
	past the end. In cases where the base is a vector of pointers the			past the end. The only in bounds address for a null pointer in the
	``inbounds`` keyword applies to each of the computations element-wise.			default address-space is the null pointer itself. In cases where the
				base is a vector of pointers the ``inbounds`` keyword applies to each
				of the computations element-wise.

	If the ``inbounds`` keyword is not present, the offsets are added to the			If the ``inbounds`` keyword is not present, the offsets are added to the
	base address with silently-wrapping two's complement arithmetic. If the			base address with silently-wrapping two's complement arithmetic. If the
	offsets have a different width from the pointer, they are sign-extended			offsets have a different width from the pointer, they are sign-extended
	or truncated to the width of the pointer. The result value of the			or truncated to the width of the pointer. The result value of the
	``getelementptr`` may be outside the object pointed to by the base			``getelementptr`` may be outside the object pointed to by the base
	pointer. The result value may not necessarily be used to access memory			pointer. The result value may not necessarily be used to access memory
	though, even if it happens to point into allocated storage. See the			though, even if it happens to point into allocated storage. See the
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