[PATCH] D156397: [FunctionAttrs] Unconditionally perform argument attribute inference in the first function-attrs pass

[Changpeng Fang via Phabricator via llvm-commits]

cfang created this revision.
cfang added reviewers: nikic, aeubanks, arsenm, bcahoon.
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Argument attributes like NoAlias and ReadOnly could affect memoryssa and thus earlyCSE in the function simplification pipeline.
https://reviews.llvm.org/D145210 adjusted PostOrderFunctionAttrs placement and caused the argument attributes not referred for the use
in the pipeline. This work (initiated by @nikic) unconditionally performs argument attribute inference in the first function-attrs pass.

Based on @nikic's experiment, the compile-time impact is pretty low: http://llvm-compile-time-tracker.com/compare.php?from=74258f4189e2b6bacabd40ee6f588fd9d1b37741&to=7f7484aee497cdae817b4aa24aed8046f430a816&stat=instructions%3Au


https://reviews.llvm.org/D156397

Files:
  llvm/lib/Transforms/IPO/FunctionAttrs.cpp
  llvm/test/Transforms/InstCombine/unused-nonnull.ll
  llvm/test/Transforms/PhaseOrdering/arg-attrs-affect-earlycse.ll

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