[PATCH] D68492: [PATCH 09/38] [noalias] D9376: llvm.noalias - handling of dead intrinsics
Jeroen Dobbelaere via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 10 14:05:50 PDT 2019
jeroen.dobbelaere marked an inline comment as done.
jeroen.dobbelaere added inline comments.
================
Comment at: llvm/lib/Analysis/InstructionSimplify.cpp:5156
+ if (isa<UndefValue>(Arg0) ||
+ (isa<ConstantPointerNull>(Arg0) &&
+ Arg0->getType()->getPointerAddressSpace() == 0))
----------------
a.elovikov wrote:
> What if we have
>
> %i = ptr2int %p
> %null = sub %i, %i
> %nullptr = int2ptr %null
> %scope = call @llvm.noalias(%nullptr) ; introduce the scope
> %null2 = ptr2int %scope
> %i2 = add %null2, %i
> %same.as.orig.p = int2ptr %i2
>
> Why don't we want `%same.as.orig.p` to have the scope?
A ptr2int will normally block the noalias propagation. Not sure if a
%same.as.orig.p = getelementptr %scope, %i
is valid when %scope is null. If that is valid, the noalias dependency should not be removed, and we should not short-circuit it here.
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https://reviews.llvm.org/D68492/new/
https://reviews.llvm.org/D68492
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