[llvm-bugs] [Bug 45572] New: Interleave failure in Loop Vectorizer

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45572

            Bug ID: 45572
           Summary: Interleave failure in Loop Vectorizer
           Product: libraries
           Version: 10.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Loop Optimizer
          Assignee: unassignedbugs at nondot.org
          Reporter: quic_abhikran at quicinc.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 23370
  --> https://bugs.llvm.org/attachment.cgi?id=23370&action=edit
IR to reproduce the error

Hello,

I'm observing a problem with load instruction being vectorized(by Loop
Vectorizer) but erroring out because of the below mentioned error:

Error message :: void
llvm::InnerLoopVectorizer::vectorizeMemoryInstruction(llvm::Instruction*,
llvm::VPTransformState&, llvm::VPValue*, llvm::VPValue*, llvm::VPValue*):
Assertion `(Decision == LoopVectorizationCostModel::CM_Widen || Decision ==
LoopVectorizationCostModel::CM_Widen_Reverse || Decision ==
LoopVectorizationCostModel::CM_GatherScatter) && "CM decision is not to widen
the memory instruction"' failed.

Source code ::
https://github.com/llvm/llvm-project/blob/master/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp#L2373 

The problem is observed because Decision variable is set to CM_Interleave.
While debugging, I found out that the decision is being set to CM_Interleave in
the following
line(https://github.com/llvm/llvm-project/blob/master/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp#L6088
). But, CM_Interleave decision type is not supported in
InnerLoopVectorizer::vectorizeMemoryInstruction function. 

The attached file(vect.ll) is able to reproduce the error from LLVM master
branch.

Command to reproduce the error: 

     ./opt -loop-vectorize -hexagon-autohvx=1 vect.ll -S

Thanks,
Abhikrant

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