[llvm-commits] [llvm] r169783 - /llvm/trunk/utils/TableGen/DFAPacketizerEmitter.cpp

[David Blaikie]

On Mon, Dec 10, 2012 at 2:45 PM, Anshuman Dasgupta
<adasgupt at codeaurora.org> wrote:
> Author: adasgupt
> Date: Mon Dec 10 16:45:57 2012
> New Revision: 169783
>
> URL: http://llvm.org/viewvc/llvm-project?rev=169783&view=rev
> Log:
> Fix PR14568: Avoid the DFA packetizer from making an invalid read
> beyond array bounds.
>
> No test case since I cannot reproduce an ICE with this bug. According
> to Carlos -- the bug reporter -- a segfault occurs only when LLVM is
> compiled with a specific version of GCC.

Could you reproduce this under valgrind/asan/etc? A test case that
would fail under such tools wouldn't be a bad thing to add.

>
> Modified:
>     llvm/trunk/utils/TableGen/DFAPacketizerEmitter.cpp
>
> Modified: llvm/trunk/utils/TableGen/DFAPacketizerEmitter.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/utils/TableGen/DFAPacketizerEmitter.cpp?rev=169783&r1=169782&r2=169783&view=diff
> ==============================================================================
> --- llvm/trunk/utils/TableGen/DFAPacketizerEmitter.cpp (original)
> +++ llvm/trunk/utils/TableGen/DFAPacketizerEmitter.cpp Mon Dec 10 16:45:57 2012
> @@ -279,6 +279,7 @@
>  //
>  //
>  void DFA::writeTableAndAPI(raw_ostream &OS, const std::string &TargetName) {
> +  static const std::string SentinelEntry = "{-1, -1}";
>    DFA::StateSet::iterator SI = states.begin();
>    // This table provides a map to the beginning of the transitions for State s
>    // in DFAStateInputTable.
> @@ -305,12 +306,17 @@
>      // If there are no valid transitions from this stage, we need a sentinel
>      // transition.
>      if (ValidTransitions == StateEntry[i]) {
> -      OS << "{-1, -1},";
> +      OS << SentinelEntry << ",";
>        ++ValidTransitions;
>      }
>
>      OS << "\n";
>    }
> +
> +  // Print out a sentinel entry at the end of the StateInputTable. This is
> +  // needed to iterate over StateInputTable in DFAPacketizer::ReadTable()
> +  OS << SentinelEntry << "\n";
> +
>    OS << "};\n\n";
>    OS << "const unsigned int " << TargetName << "DFAStateEntryTable[] = {\n";
>
> @@ -319,6 +325,9 @@
>    for (unsigned i = 0; i < states.size(); ++i)
>      OS << StateEntry[i] << ", ";
>
> +  // Print out the index to the sentinel entry in StateInputTable
> +  OS << ValidTransitions << ", ";
> +
>    OS << "\n};\n";
>    OS << "} // namespace\n";
>
>
>
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