[llvm] r188883 - MC CFG: When disassembly is impossible, fallback to data bytes.

[Ahmed Bougacha]

On Wed, Aug 21, 2013 at 10:29 AM, David Blaikie <dblaikie at gmail.com> wrote:
> On Wed, Aug 21, 2013 at 12:28 AM, Ahmed Bougacha
> <ahmed.bougacha at gmail.com> wrote:
>> Author: ab
>> Date: Wed Aug 21 02:28:32 2013
>> New Revision: 188883
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=188883&view=rev
>> Log:
>> MC CFG: When disassembly is impossible, fallback to data bytes.
>
> Missing test case.

Yep, was working on the testcase, r188925.

-- Ahmed

>> This is the behavior of sequential disassemblers (llvm-objdump, ...),
>> when there is no instruction size hint (fixed-length, ...)
>>
>> While there, also do some minor cleanup.
>
> More text about what the cleanup was, and/or doing it in a separate
> patch would be good.
>
>>
>> Modified:
>>     llvm/trunk/lib/MC/MCObjectDisassembler.cpp
>>
>> Modified: llvm/trunk/lib/MC/MCObjectDisassembler.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCObjectDisassembler.cpp?rev=188883&r1=188882&r2=188883&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/MC/MCObjectDisassembler.cpp (original)
>> +++ llvm/trunk/lib/MC/MCObjectDisassembler.cpp Wed Aug 21 02:28:32 2013
>> @@ -102,19 +102,29 @@ void MCObjectDisassembler::buildSectionA
>>      StringRef SecName; SI->getName(SecName);
>>
>>      if (isText) {
>> -      MCTextAtom *Text = Module->createTextAtom(StartAddr, EndAddr);
>> -      Text->setName(SecName);
>> +      MCTextAtom *Text = 0;
>> +      MCDataAtom *InvalidData = 0;
>> +
>>        uint64_t InstSize;
>>        for (uint64_t Index = 0; Index < SecSize; Index += InstSize) {
>> +        const uint64_t CurAddr = StartAddr + Index;
>>          MCInst Inst;
>> -        if (Dis.getInstruction(Inst, InstSize, memoryObject, Index,
>> -                               nulls(), nulls()))
>> +        if (Dis.getInstruction(Inst, InstSize, memoryObject, CurAddr, nulls(),
>> +                               nulls())) {
>> +          if (!Text) {
>> +            Text = Module->createTextAtom(CurAddr, CurAddr);
>> +            Text->setName(SecName);
>> +          }
>>            Text->addInst(Inst, InstSize);
>> -        else
>> -          // We don't care about splitting mixed atoms either.
>> -          llvm_unreachable("Couldn't disassemble instruction in atom.");
>> +          InvalidData = 0;
>> +        } else {
>> +          if (!InvalidData) {
>> +            Text = 0;
>> +            InvalidData = Module->createDataAtom(CurAddr, EndAddr);
>> +          }
>> +          InvalidData->addData(Contents[Index]);
>> +        }
>>        }
>> -
>>      } else {
>>        MCDataAtom *Data = Module->createDataAtom(StartAddr, EndAddr);
>>        Data->setName(SecName);
>> @@ -134,6 +144,8 @@ namespace {
>>      BBInfoSetTy Succs;
>>      BBInfoSetTy Preds;
>>
>> +    BBInfo() : Atom(0), BB(0) {}
>> +
>>      void addSucc(BBInfo &Succ) {
>>        Succs.insert(&Succ);
>>        Succ.Preds.insert(this);
>> @@ -232,8 +244,8 @@ void MCObjectDisassembler::buildCFG(MCMo
>>      // Create MCBBs.
>>      SmallSetVector<BBInfo*, 16> Worklist;
>>      Worklist.insert(&BBI);
>> -    for (size_t WI = 0; WI < Worklist.size(); ++WI) {
>> -      BBInfo *BBI = Worklist[WI];
>> +    for (size_t wi = 0; wi < Worklist.size(); ++wi) {
>> +      BBInfo *BBI = Worklist[wi];
>>        if (!BBI->Atom)
>>          continue;
>>        BBI->BB = &MCFN.createBlock(*BBI->Atom);
>> @@ -247,17 +259,19 @@ void MCObjectDisassembler::buildCFG(MCMo
>>      }
>>
>>      // Set preds/succs.
>> -    for (size_t WI = 0; WI < Worklist.size(); ++WI) {
>> -      BBInfo *BBI = Worklist[WI];
>> +    for (size_t wi = 0; wi < Worklist.size(); ++wi) {
>> +      BBInfo *BBI = Worklist[wi];
>>        MCBasicBlock *MCBB = BBI->BB;
>>        if (!MCBB)
>>          continue;
>>        for (BBInfoSetTy::iterator SI = BBI->Succs.begin(), SE = BBI->Succs.end();
>> -                                 SI != SE; ++SI)
>> -        MCBB->addSuccessor((*SI)->BB);
>> +           SI != SE; ++SI)
>> +        if ((*SI)->BB)
>> +          MCBB->addSuccessor((*SI)->BB);
>>        for (BBInfoSetTy::iterator PI = BBI->Preds.begin(), PE = BBI->Preds.end();
>> -                                 PI != PE; ++PI)
>> -        MCBB->addPredecessor((*PI)->BB);
>> +           PI != PE; ++PI)
>> +        if ((*PI)->BB)
>> +          MCBB->addPredecessor((*PI)->BB);
>>      }
>>    }
>>  }
>>
>>
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