[LLVMbugs] [Bug 5934] New: Incorrect atomic op codegen for (buggy) Opterons

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=5934

           Summary: Incorrect atomic op codegen for (buggy) Opterons
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Backend: X86
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: resistor at mac.com
                CC: llvmbugs at cs.uiuc.edu


Apparently some Opterons have a memory consistency bug where a locked
instruction followed by a non-locked RMW instruction can violate consistency
guarantees.  The work around is to emit an lfence between the two.

Should we consider generating code with the fix?

Reference for the Operton bug: line 99 of
http://code.google.com/p/google-perftools/source/browse/trunk/src/base/atomicops-internals-x86.cc


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