[LLVMbugs] [Bug 13242] New: malloc (not alloca) optimization issue

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13242

             Bug #: 13242
           Summary: malloc (not alloca) optimization issue
           Product: new-bugs
           Version: 3.1
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: jimjim211112 at yahoo.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 8796
  --> http://llvm.org/bugs/attachment.cgi?id=8796
C code running slow.

Hello fellow human beings.

Have attached some code. When compiling using clang with flags -O3 it produces
slow code.
If I change the malloc to alloca it produces fast (instant running time) code.
If commenting out one of the assignment in fac() function it is running fast
with malloc.

Using gcc instead of clang produces fast code with malloc.
Have I missed an optimization flag or is there something weird going on?

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