https://bugs.llvm.org/show_bug.cgi?id=46261
Bug ID: 46261
Summary: [SLP] SLP vectorizer change causes performance loss
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: wolfgang_p...@playstation.sony.com
CC: llvm-bugs@lists.llvm.org
Created attachment 23593
--> https://bugs.llvm.org/attachment.cgi?id=23593&action=edit
Test case
After the commit
https://github.com/llvm/llvm-project/commit/6a18a9548761b266b28a49f705a568677c24b59b
the attached test experiences a roughly 50% slowdown.
Compile with clang -O2 -march=btver2.
The IR dump after SLP shows that, before the commit, a substantial number of
shuffle instructions are present, e.g.
%shuffle = shufflevector <2 x float> %14, <2 x float> undef, <4 x i32> <i32 0,
i32 0, i32 0, i32 1>
whereas after the commit, the IR dump does not show any.
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