[LLVMbugs] [Bug 19932] New: X86InstrInfo.cpp:3791: valgrind problems

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Jun 3 08:04:55 PDT 2014


            Bug ID: 19932
           Summary: X86InstrInfo.cpp:3791: valgrind problems
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: dcb314 at hotmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 12597
  --> http://llvm.org/bugs/attachment.cgi?id=12597&action=edit
C source code

Attached source code, when compiled with flag -O2 by trunk dated 20140602,
running under valgrind, says

==20797== Conditional jump or move depends on uninitialised value(s)
==20797==    at 0x1CC7A9A:
eInstr*, unsigned int, unsigned int, int, int, llvm::MachineRegisterInfo
 const (X86InstrInfo.cpp:3791)
==20797==    by 0x1FBDD31: (anonymous
eFunction(llvm::MachineFunction&) (PeepholeOptimizer.cpp:322)
==20797==    by 0x2562BA8: llvm::FPPassManager::runOnFunction(llvm::Function&)
==20797==    by 0x256334A: llvm::legacy::PassManagerImpl::run(llvm::Module&)

X86InstrInfo.cpp:3791 is

    if ((ShouldUpdateCC || IsSwapped) && NewCC != OldCC) {

I checked all of these local variables and OldCC was the only
one that wasn't initialised at its declaration. 

That might be the smoking gun.

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