[llvm] r175688 - Kill of TransferDeadFlag - Dead copies and subreg-to-reg instructions should
Lang Hames
lhames at gmail.com
Thu Feb 21 09:07:35 PST 2013
Hi Alexy, Duncan,
Thanks for catching this. I've reverted it in r175765.
The existing TransferDeadFlag code is broken - Targets are free to replace
copies and subreg-to-reg instructions with instructions that define
super-regs. In that case TransferDeadFlag will either crash, or (worse) may
tag an unrelated earlier definition as dead. I'll track down whatever is
wrong with this fix and re-apply.
Cheers,
Lang.
On Thu, Feb 21, 2013 at 4:22 AM, Duncan Sands <baldrick at free.fr> wrote:
> On 21/02/13 12:21, Alexey Samsonov wrote:
>
>> Hi, Lang!
>>
>> I think this is causing http://llvm.org/bugs/show_bug.**cgi?id=15320<http://llvm.org/bugs/show_bug.cgi?id=15320>.
>> Could you
>> please take a look?
>>
>
> Vast numbers of dragonegg buildbots are showing a miscompilation, and this
> commit is in the blame list... So I also ask you to please take a look!
>
> Ciao, Duncan.
>
>
>>
>> On Thu, Feb 21, 2013 at 3:36 AM, Lang Hames <lhames at gmail.com
>> <mailto:lhames at gmail.com>> wrote:
>>
>> Author: lhames
>> Date: Wed Feb 20 17:36:57 2013
>> New Revision: 175688
>>
>> URL: http://llvm.org/viewvc/llvm-**project?rev=175688&view=rev<http://llvm.org/viewvc/llvm-project?rev=175688&view=rev>
>> Log:
>> Kill of TransferDeadFlag - Dead copies and subreg-to-reg instructions
>> should
>> just be turned into kills on the spot.
>>
>>
>> Modified:
>> llvm/trunk/lib/CodeGen/**ExpandPostRAPseudos.cpp
>>
>> Modified: llvm/trunk/lib/CodeGen/**ExpandPostRAPseudos.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-**project/llvm/trunk/lib/**
>> CodeGen/ExpandPostRAPseudos.**cpp?rev=175688&r1=175687&r2=**
>> 175688&view=diff<http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/ExpandPostRAPseudos.cpp?rev=175688&r1=175687&r2=175688&view=diff>
>> ==============================**==============================**
>> ==================
>> --- llvm/trunk/lib/CodeGen/**ExpandPostRAPseudos.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/**ExpandPostRAPseudos.cpp Wed Feb 20
>> 17:36:57 2013
>> @@ -49,8 +49,6 @@ private:
>> bool LowerSubregToReg(MachineInstr *MI);
>> bool LowerCopy(MachineInstr *MI);
>>
>> - void TransferDeadFlag(MachineInstr *MI, unsigned DstReg,
>> - const TargetRegisterInfo *TRI);
>> void TransferImplicitDefs(**MachineInstr *MI);
>> };
>> } // end anonymous namespace
>> @@ -61,21 +59,6 @@ char &llvm::ExpandPostRAPseudosID = Expa
>> INITIALIZE_PASS(ExpandPostRA, "postrapseudos",
>> "Post-RA pseudo instruction expansion pass", false,
>> false)
>>
>> -/// TransferDeadFlag - MI is a pseudo-instruction with DstReg dead,
>> -/// and the lowered replacement instructions immediately precede it.
>> -/// Mark the replacement instructions with the dead flag.
>> -void
>> -ExpandPostRA::**TransferDeadFlag(MachineInstr *MI, unsigned DstReg,
>> - const TargetRegisterInfo *TRI) {
>> - for (MachineBasicBlock::iterator MII =
>> - prior(MachineBasicBlock::**iterator(MI)); ; --MII) {
>> - if (MII->addRegisterDead(DstReg, TRI))
>> - break;
>> - assert(MII != MI->getParent()->begin() &&
>> - "copyPhysReg output doesn't reference destination
>> register!");
>> - }
>> -}
>> -
>> /// TransferImplicitDefs - MI is a pseudo-instruction, and the
>> lowered
>> /// replacement instructions immediately precede it. Copy any
>> implicit-def
>> /// operands from MI to the replacement instruction.
>> @@ -128,17 +111,17 @@ bool ExpandPostRA::**LowerSubregToReg(Mach
>> }
>> DEBUG(dbgs() << "subreg: eliminated!");
>> } else {
>> + if (MI->getOperand(0).isDead()) {
>> + MI->setDesc(TII->get(**TargetOpcode::KILL));
>> + DEBUG(dbgs() << "subreg: replaced by: " << *MI);
>> + return true;
>> + }
>> TII->copyPhysReg(*MBB, MI, MI->getDebugLoc(), DstSubReg, InsReg,
>> MI->getOperand(2).isKill());
>> -
>> // Implicitly define DstReg for subsequent uses.
>> MachineBasicBlock::iterator CopyMI = MI;
>> --CopyMI;
>> CopyMI->addRegisterDefined(**DstReg);
>> -
>> - // Transfer the kill/dead flags, if needed.
>> - if (MI->getOperand(0).isDead())
>> - TransferDeadFlag(MI, DstSubReg, TRI);
>> DEBUG(dbgs() << "subreg: " << *CopyMI);
>> }
>>
>> @@ -151,11 +134,18 @@ bool ExpandPostRA::LowerCopy(**MachineInst
>> MachineOperand &DstMO = MI->getOperand(0);
>> MachineOperand &SrcMO = MI->getOperand(1);
>>
>> + if (DstMO.isDead()) {
>> + DEBUG(dbgs() << "dead copy: " << *MI);
>> + MI->setDesc(TII->get(**TargetOpcode::KILL));
>> + DEBUG(dbgs() << "replaced by: " << *MI);
>> + return true;
>> + }
>> +
>> if (SrcMO.getReg() == DstMO.getReg()) {
>> DEBUG(dbgs() << "identity copy: " << *MI);
>> // No need to insert an identity copy instruction, but replace
>> with a KILL
>> // if liveness is changed.
>> - if (DstMO.isDead() || SrcMO.isUndef() || MI->getNumOperands() >
>> 2) {
>> + if (SrcMO.isUndef() || MI->getNumOperands() > 2) {
>> // We must make sure the super-register gets killed. Replace
>> the
>> // instruction with KILL.
>> MI->setDesc(TII->get(**TargetOpcode::KILL));
>> @@ -171,8 +161,6 @@ bool ExpandPostRA::LowerCopy(**MachineInst
>> TII->copyPhysReg(*MI->**getParent(), MI, MI->getDebugLoc(),
>> DstMO.getReg(), SrcMO.getReg(), SrcMO.isKill());
>>
>> - if (DstMO.isDead())
>> - TransferDeadFlag(MI, DstMO.getReg(), TRI);
>> if (MI->getNumOperands() > 2)
>> TransferImplicitDefs(MI);
>> DEBUG({
>>
>>
>> ______________________________**_________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu <mailto:llvm-commits at cs.uiuc.**edu<llvm-commits at cs.uiuc.edu>
>> >
>>
>> http://lists.cs.uiuc.edu/**mailman/listinfo/llvm-commits<http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>
>>
>>
>>
>>
>> --
>> Alexey Samsonov, MSK
>>
>>
>> ______________________________**_________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/**mailman/listinfo/llvm-commits<http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>
>>
>>
> ______________________________**_________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/**mailman/listinfo/llvm-commits<http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20130221/ec46282f/attachment.html>
More information about the llvm-commits
mailing list