[llvm-bugs] [Bug 48051] New: [OssFuzz Issue 26832] "No point in having a non-constant max backedge taken count!"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48051

            Bug ID: 48051
           Summary: [OssFuzz Issue 26832] "No point in having a
                    non-constant max backedge taken count!"
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: lebedev.ri at gmail.com, llvm-bugs at lists.llvm.org,
                    nikita.ppv at gmail.com, spatel+llvm at rotateright.com

Reduced from https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=26832

opt -irce

opt: /home/simon/LLVM/llvm-project/llvm/lib/Analysis/ScalarEvolution.cpp:7000:
llvm::ScalarEvolution::ExitLimit::ExitLimit(const llvm::SCEV*, const
llvm::SCEV*, bool, llvm::ArrayRef<const llvm::SmallPtrSetImpl<const
llvm::SCEVPredicate*>*>): Assertion `(isa<SCEVCouldNotCompute>(MaxNotTaken) ||
isa<SCEVConstant>(MaxNotTaken)) && "No point in having a non-constant max
backedge taken count!"' failed.

define void @scalar_after_vectorization_0() {
outer.ph:
  br label %outer.body

outer.body:                                       ; preds = %inner.end,
%outer.ph
  %i = phi i64 [ 1, %outer.ph ], [ %i.next, %inner.end ]
  %tmp0 = mul nuw nsw i64 %i, undef
  br label %inner.body

inner.body:                                       ; preds = %inner.body,
%outer.body
  %j = phi i64 [ 1, %outer.body ], [ %tmp1, %inner.body ]
  %tmp1 = add nuw nsw i64 %j, %tmp0
  %B3 = mul i64 %tmp1, undef
  %B13 = mul i64 %B3, 4294967296
  %C2 = icmp slt i64 undef, %B13
  br i1 %C2, label %inner.body, label %inner.end

inner.end:                                        ; preds = %inner.body
  %B4 = sub i64 9223372036854775807, -9223372036854775808
  %B21 = and i64 %B4, %B4
  %B9 = lshr i64 9223372036854775807, -1
  %B16 = urem i64 %B4, %B9
  %i.next = add i64 %i, %B16
  %C = icmp ult i64 %B21, %i.next
  br i1 %C, label %outer.body, label %outer.end

outer.end:                                        ; preds = %inner.end
  ret void
}

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