On Mon, 16 Jul 2012, Andreas Hansson wrote:
More info from valgrind for the x86 linux boot:
==12647== Conditional jump or move depends on uninitialised value(s)
==12647== at 0x430399: X86ISA::RegOpBase::genFlags(unsigned long,
unsigned long, unsigned long, unsigned long, unsigned long, bool) const
(microregop.cc:73) ==12647== by 0x93118D:
X86ISAInst::SubFlagsBig::execute(TimingSimpleCPU*, Trace::InstRecord*)
const (timing_simple_cpu_exec.cc:3807) ==12647== by 0xE904DE:
TimingSimpleCPU::completeIfetch(Packet*) (timing.cc:685)
Plus plenty more of these on similar lines in microregop.cc.
Any clues (for those who know that part of the codebase)?
I ran Valgrind with track-origins set to yes. The output is similar to
what Andreas got, the only addition being that the uninitialised value is
being created in the function CPUID::execute(). I can see that the result
variable in that function is not initialised, and that it is possible that
the doCpuid() function in file src/arch/x86/cpuid.cc returns this
uninitialised value. It seems we need an else condition at the end of the
function.
==27145==
==27145== Conditional jump or move depends on uninitialised value(s)
==27145== at 0xACB026: X86ISA::RegOpBase::genFlags(unsigned long,
unsigned long, unsigned long, unsigned long, unsigned long, bool) const
(microregop.cc:75)
==27145== by 0xFB25CA:
X86ISAInst::SubFlagsBig::execute(TimingSimpleCPU*, Trace::InstRecord*)
const (timing_simple_cpu_exec.cc:3807)
==27145== by 0x615A17: TimingSimpleCPU::completeIfetch(Packet*)
(timing.cc:685)
==27145== by 0x6137B1: TimingSimpleCPU::fetch() (timing.cc:566)
==27145== by 0x6150E0:
TimingSimpleCPU::advanceInst(RefCountingPtr<FaultBase>) (timing.cc:629)
==27145== by 0x615B98: TimingSimpleCPU::completeIfetch(Packet*)
(timing.cc:700)
==27145== by 0x616234:
TimingSimpleCPU::IcachePort::recvTimingResp(Packet*) (timing.cc:726)
==27145== by 0x6FC0D6: SlavePort::sendTimingResp(Packet*) (port.cc:215)
==27145== by 0x6FD090: SlavePacketQueue::sendTiming(Packet*, bool)
(packet_queue.cc:235)
==27145== by 0x6FCD09: PacketQueue::trySendTiming()
(packet_queue.cc:147)
==27145== by 0x6FCE8F: PacketQueue::sendDeferredPacket()
(packet_queue.cc:183)
==27145== by 0x6FCEFB: PacketQueue::processSendEvent()
(packet_queue.cc:196)
==27145== Uninitialised value was created by a stack allocation
==27145== at 0x1008DBE: X86ISAInst::CPUID::execute(TimingSimpleCPU*,
Trace::InstRecord*) const (timing_simple_cpu_exec.cc:20864)
--
Nilay
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