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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">I see the problem. There's two members of Op->RegIdx that aren't copied in the new version of CreateRegPair().<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> NAKAMURA Takumi [mailto:geek4civic@gmail.com]
<br>
<b>Sent:</b> 09 May 2016 17:15<br>
<b>To:</b> Daniel Sanders; Benjamin Kramer; Zlatko Buljan; llvm-commits@lists.llvm.org<br>
<b>Subject:</b> Re: [llvm] r268896 - [mips][microMIPS] Implement LWP and SWP instructions<o:p></o:p></span></p>
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<p class="MsoNormal">It seems this still causes undefined behavior after fixes.<br>
<br>
This is the log with MC/Mips/micromips-loadstore-instructions.s.<o:p></o:p></p>
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<p class="MsoNormal">==55344== Conditional jump or move depends on uninitialised value(s)<o:p></o:p></p>
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<p class="MsoNormal">==55344== at 0x54A6C5: (anonymous namespace)::MipsOperand::addRegPairOperands(llvm::MCInst&, unsigned int) const (MipsAsmParser.cpp:1010)<o:p></o:p></p>
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<p class="MsoNormal">==55344== by 0x56A55A: (anonymous namespace)::MipsAsmParser::convertToMCInst(unsigned int, llvm::MCInst&, unsigned int, llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand> > >
const&) (MipsGenAsmMatcher.inc:1306)<o:p></o:p></p>
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<p class="MsoNormal">==55344== by 0x577314: (anonymous namespace)::MipsAsmParser::MatchInstructionImpl(llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand> > > const&, llvm::MCInst&, unsigned long&,
bool, unsigned int) (MipsGenAsmMatcher.inc:6342)<o:p></o:p></p>
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<p class="MsoNormal">==55344== by 0x554808: (anonymous namespace)::MipsAsmParser::MatchAndEmitInstruction(llvm::SMLoc, unsigned int&, llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand> > >&, llvm::MCStreamer&,
unsigned long&, bool) (MipsAsmParser.cpp:3671)<o:p></o:p></p>
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<p class="MsoNormal">==55344== by 0x84F03C: (anonymous namespace)::AsmParser::parseStatement((anonymous namespace)::ParseStatementInfo&, llvm::MCAsmParserSemaCallback*) (AsmParser.cpp:1838)<o:p></o:p></p>
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<p class="MsoNormal">==55344== by 0x848F11: (anonymous namespace)::AsmParser::Run(bool, bool) (AsmParser.cpp:675)<o:p></o:p></p>
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<p class="MsoNormal">==55344== by 0x405F2F: AssembleInput(char const*, llvm::Target const*, llvm::SourceMgr&, llvm::MCContext&, llvm::MCStreamer&, llvm::MCAsmInfo&, llvm::MCSubtargetInfo&, llvm::MCInstrInfo&, llvm::MCTargetOptions&) (llvm-mc.cpp:364)<o:p></o:p></p>
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<p class="MsoNormal">==55344== by 0x4070D8: main (llvm-mc.cpp:536)<o:p></o:p></p>
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<p class="MsoNormal">On Mon, May 9, 2016 at 10:27 PM Daniel Sanders via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org">llvm-commits@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">> > @@ -4673,9 +4692,9 @@ MipsAsmParser::parseRegisterPair(Operand<br>
> ><br>
> > SMLoc E = Parser.getTok().getLoc();<br>
> > MipsOperand &Op = static_cast<MipsOperand &>(*Operands.back());<br>
> > - unsigned Reg = Op.getGPR32Reg();<br>
> > +<br>
> > Operands.pop_back();<br>
> > - Operands.push_back(MipsOperand::CreateRegPair(Reg, S, E, *this));<br>
> > + Operands.push_back(MipsOperand::CreateRegPair(Op, S, E, *this));<br>
><br>
> There's a use after free here because Op is still bound to<br>
> Operands.back(). I tried to fix in r268901, but it broke tests. Can you take a look?<br>
<br>
I've applied a quick fix for this in r268913. Op is now a copy of the last element so that Op isn't deleted when pop_back() causes std::unique_ptr<MipsOperand> to delete Operands.back().<br>
<br>
I'm not sure why your fix didn't work. It looked ok to me.<br>
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