https://llvm.org/bugs/show_bug.cgi?id=26564
Bug ID: 26564
Summary: Performance regression in AA
Product: new-bugs
Version: 3.8
Hardware: PC
OS: Linux
Status: NEW
Keywords: performance
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: bstei...@gmail.com
CC: chandl...@gmail.com, llvm-bugs@lists.llvm.org
Classification: Unclassified
Since upgrading to a more recent LLVM version for the Rust compiler, there has
been a large increase in compile time spent in LLVM optimizations. The
corresponding Rust bug report can be found here:
https://github.com/rust-lang/rust/issues/31435
At least part of that seems to come from the new AA handling, which exhibits
O(n^2) behavior in some cases with n being the number of active AA passes.
This originates from using the AAResultProxy in the AAResultBase class. For
example, calling AAResults::getModRefBehavior(CallSite) will iterate over all
registered AA results which all may eventually call into
AAResultBase::getModRefBehavior(CallSite) which calls
AAResultProxy::getModRefBehavior(Function*) which will then iterate over all
registered passes again.
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