Peter Collingbourne 74eabdd998 Introduce llvm.load.relative intrinsic. ...

This intrinsic takes two arguments, ``%ptr`` and ``%offset``. It loads
a 32-bit value from the address ``%ptr + %offset``, adds ``%ptr`` to that
value and returns it. The constant folder specifically recognizes the form of
this intrinsic and the constant initializers it may load from; if a loaded
constant initializer is known to have the form ``i32 trunc(x - %ptr)``,
the intrinsic call is folded to ``x``.

LLVM provides that the calculation of such a constant initializer will
not overflow at link time under the medium code model if ``x`` is an
``unnamed_addr`` function. However, it does not provide this guarantee for
a constant initializer folded into a function body. This intrinsic can be
used to avoid the possibility of overflows when loading from such a constant.

Differential Revision: http://reviews.llvm.org/D18367

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267223 91177308-0d34-0410-b5e6-96231b3b80d8

2016-04-22 21:18:02 +00:00

..

llvm

Introduce llvm.load.relative intrinsic.

2016-04-22 21:18:02 +00:00

llvm-c

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