[LLVMbugs] [Bug 14448] New: [loopvectorize] multiple vector loops generated from single scalar loop

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Wed Nov 28 11:35:39 PST 2012


             Bug #: 14448
           Summary: [loopvectorize] multiple vector loops generated from
                    single scalar loop
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Keywords: code-quality
          Severity: enhancement
          Priority: P
         Component: Loop Optimizer
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: paul.redmond at intel.com
                CC: llvmbugs at cs.uiuc.edu, nrotem at apple.com
    Classification: Unclassified

I think this is a known issue but..

If you compile the following program with vectorize-loops enabled multiple
vector loops are generated because the scalar loop is processed by
LoopVectorize twice.

#include <numeric>

int foo(int *A, int n)
  return std::accumulate(A, A + n, 0);

The generated code is correct but not desirable.

compile with:
clang++ -S -emit-llvm accum.cpp -O2 -mllvm -vectorize-loops -o -

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