[llvm-bugs] [Bug 48212] New: Loop-Interchange crashes if the first phi node of a header is not an induction node

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48212

            Bug ID: 48212
           Summary: Loop-Interchange crashes if the first phi node of a
                    header is not an induction node
           Product: tools
           Version: 11.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: opt
          Assignee: unassignedbugs at nondot.org
          Reporter: flemairen6 at gmail.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 24179
  --> https://bugs.llvm.org/attachment.cgi?id=24179&action=edit
IR file that causes the crash to happen.

$ clang test.c -Xclang -disable-O0-optnone -emit-llvm -O0 -S -o test.ll
$ opt -mem2reg -loop-rotate -loop-interchange test.ll

opt: llvm-project/llvm/lib/Transforms/Scalar/LoopInterchange.cpp:1583: bool
(anonymous namespace)::LoopInterchangeTransform::adjustLoopBranches():
Assertion `OuterInnerReductions.find(PHI) != OuterInnerReductions.end() &&
"Expected a reduction PHI node"' failed.

And then there is the stacktrace. 

test.c : 

void foo (int filter[5][5]){
    int k1, k2;
    int temp, mul;
    L1:for (k1=0;k1<5;k1++){
        L2:for (k2=0;k2<3;k2++){
           mul = filter[k2][k1];
           temp += mul;
        }
    }
}

int main() {
  int filter[5][5];
  foo(filter);
}

Build :

LLVM (http://llvm.org/):
  LLVM version 11.0.0git
  DEBUG build with assertions.
  Default target: x86_64-unknown-linux-gnu
  Host CPU: skylake

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