https://bugs.llvm.org/show_bug.cgi?id=39903
Bug ID: 39903
Summary: Vectorization generates unaligned moves for properly
aligned data
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: jamesma...@gmail.com
CC: llvm-bugs@lists.llvm.org, neeil...@live.com,
richard-l...@metafoo.co.uk
Created attachment 21198
--> https://bugs.llvm.org/attachment.cgi?id=21198&action=edit
Code that shows the problem in compiler explorer.
A simple FMA loop operating on data that is aligned with `alignas(64)` is
generating `vmovups` instructions when it could, and should, be generating
`vmovaps`.
Since the nehalem architecture the cost of a `vmovups` relative to `vmovaps` is
not as large as it once was, but it is noticeable and if the data is guaranteed
to be aligned, then `vmovaps` should be the instruction used.
https://www.godbolt.org/z/CCcjYu
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