[PATCH] D38925: Fix implicit null check with negative offset

[Yichao Yu via Phabricator via llvm-commits]

yuyichao created this revision.

It seems that negative offset was accidentally allowed in https://reviews.llvm.org/D17967.
AFAICT small negative offset should be valid (always raise segfault) on all archs that I'm aware of (especially x86, which is the only one with this optimization enabled) and such case can be useful when loading hiden metadata from an object.

However, like the positive side, it should only be done within a certain limit.
For now, use the same limit on the positive side for the negative side.
A separate option can be added if needs appear.


https://reviews.llvm.org/D38925

Files:
  lib/CodeGen/ImplicitNullChecks.cpp
  test/CodeGen/X86/implicit-null-check-negative.ll
  test/CodeGen/X86/implicit-null-check.ll

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