https://bugs.llvm.org/show_bug.cgi?id=39994
Bug ID: 39994
Summary: Converting invoke to call does not transfer
"MD_mem_parallel_loop_access" metadata
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Transformation Utilities
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Hi,
We have observed a problem with vectorization and the newest LLVM/Clang trunk
(older versions seem to be affected as well). We have a loop with a potential
race condition for which we force vectorization using "#pragma clang loop
vectorize(assume_safety)." Despite that, Clang fails to vectorize our loop
reporting that it "cannot identify array bounds." After investigating the IR
after each pass, we found a potential cause of this issue. It seems like the
"MD_mem_parallel_loop_access" metadata did not get transferred over when
converting an invoke to a call. We could fix the problem by adding the
following line to the changeToCall() method in Local.cpp:
NewCall->copyMetadata(*II, LLVMContext::MD_mem_parallel_loop_access);
This is similar to to what is done in SROA, but we are not sure whether this is
a valid fix for the observed issue.
Please note that we are aware of the WIP under D52116 and D52117, but our fix
(with additional copying of "LLVMContext::MD_access_group" in the same call)
was also required to get the loop vectorized after applying those two patches.
Thanks,
Moritz
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