[LLVMbugs] [Bug 12376] New: Empty loop with undefined overflow in IV not optimized away.

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12376

             Bug #: 12376
           Summary: Empty loop with undefined overflow in IV not optimized
                    away.
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Loop Optimizer
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: benny.kra at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


>From GCC PR23361:

void foo2(int a, int b)
{ for(;a<b;a+=4); }

void foo3(int*a, int* b)
{ for(;a<b;a++); }

foo2 has the nsw bit on the IV add, foo3 has an inbounds GEP. Both loops should
be eliminated (and are currently not handled at clang -O3).

We get them when "!=" is used for the condition instead of "<".

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