[llvm-dev] [RFC][LangRef][AliasAnalysis] Clarify noalias affects only modified objects (original) (raw)

Finkel, Hal J. via llvm-dev llvm-dev at lists.llvm.org
Thu Feb 20 17🔞49 PST 2020

For AA-based memory-dependency analysis, this makes sense to me. read/read aliasing doesn't affect anything.

My only questions is: is there any concern that this might confuse instrumentation passes, or similar, which might do something even for read/read cases? Does anyone know of any other use cases that might be affected by this?

-Hal

Hal Finkel Lead, Compiler Technology and Programming Languages Leadership Computing Facility Argonne National Laboratory

From: Johannes Doerfert Sent: Thursday, February 20, 2020 5:46 PM To: LLVM-Dev Cc: Finkel, Hal J. Subject: [RFC][LangRef][AliasAnalysis] Clarify noalias affects only modified objects

I would like to clarify that noalias on arguments matches restrict in C99. In particular, objects need to be modified for the noalias to be "effective". We basically apply this reasoning already in various parts but I want to make it explicit now.

The wording change and the reasons are explained in https://reviews.llvm.org/D74935

Please let me know if there are concerns.

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