[llvm-bugs] [Bug 32135] New: Loop vectorizer miscompile
llvm-bugs at lists.llvm.org
Fri Mar 3 15:53:20 PST 2017
Bug ID: 32135
Summary: Loop vectorizer miscompile
Component: Loop Optimizer
Assignee: unassignedbugs at nondot.org
Reporter: craig.topper at gmail.com
CC: llvm-bugs at lists.llvm.org
Created attachment 18052
The attached test case produces different output when compiled at -O1 and -O2.
The power of 2 trip count of the first loop seems to be significant. Values of
64, 128, and 256 all expose the problem. 16 does not.
It's also significant that the index for the second loop is a smaller type than
the first loop. If the same index type is used for both the loop is reduced to
a single store before the loop vectorizer even runs.
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