[LLVMbugs] [Bug 2902] New: -std-compile-opt produces a CFG w/ infinite loop

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2902

           Summary: -std-compile-opt produces a CFG w/ infinite loop
           Product: tools
           Version: 2.3
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Severity: normal
          Priority: P2
         Component: opt
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: micah.villmow at amd.com
                CC: llvmbugs at cs.uiuc.edu


Created an attachment (id=2093)
 --> (http://llvm.org/bugs/attachment.cgi?id=2093)
Test case for above bug

The attached test case produces an infinite loop in the CFG when run w/
std-compile-opt

The method that this is reproducible is as follows

clang -emit-llvm test_llvm_bug_report.c
llvm-as < test_llvm_bug_report.ll | opt -std-compile-opts -print-cfg-only >
test.bc

To figure out that it was this specific test I ran through the expanded list of
options with the following set not producing the infinite loop:
-preverify  -domtree  -verify  -lowersetjmp  -raiseallocs  -simplifycfg 
-domtree  -domfrontier  -mem2reg  -globalopt  -globaldce  -ipconstprop 
-deadargelim  -instcombine  -simplifycfg  -basiccg  -prune-eh  -inline 
-argpromotion  -simplify-libcalls  -instcombine  -jump-threading  -simplifycfg 
-domtree  -domfrontier  -scalarrepl  -instcombine  -break-crit-edges  -condprop
 -tailcallelim  -simplifycfg  -reassociate  -domtree  -loops  -loopsimplify 
-domfrontier  -scalar-evolution  -lcssa  -loop-rotate  -licm  -lcssa
-simplifycfg

but adding -loopunswitch between the final -lcssa and -simplifycfg causes the
problem.


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