[llvm] r253465 - [WebAssembly] Enable register coloring and register stackifying.

[Dan Gohman via llvm-commits]

On Thu, Nov 19, 2015 at 2:38 PM, Eric Christopher <echristo at gmail.com>
wrote:

>
>
>> +  // FIXME: If scheduling has moved an ARGUMENT virtual register, move
>> it back,
>> +  // and recompute liveness. This is a temporary hack.
>> +  bool SawNonArg = false;
>> +  bool MovedArg = false;
>> +  MachineBasicBlock &EntryMBB = MF.front();
>> +  for (auto MII = EntryMBB.begin(); MII != EntryMBB.end(); ) {
>> +    MachineInstr *MI = &*MII++;
>> +    if (MI->getOpcode() == WebAssembly::ARGUMENT_I32 ||
>> +        MI->getOpcode() == WebAssembly::ARGUMENT_I64 ||
>> +        MI->getOpcode() == WebAssembly::ARGUMENT_F32 ||
>> +        MI->getOpcode() == WebAssembly::ARGUMENT_F64) {
>> +      EntryMBB.insert(EntryMBB.begin(), MI->removeFromParent());
>> +      if (SawNonArg)
>> +        MovedArg = true;
>> +    } else {
>> +      SawNonArg = true;
>> +    }
>> +  }
>> +  if (MovedArg) {
>> +    SlotIndexes &Slots = getAnalysis<SlotIndexes>();
>> +    Liveness->releaseMemory();
>> +    Slots.releaseMemory();
>> +    Slots.runOnMachineFunction(MF);
>> +    Liveness->runOnMachineFunction(MF);
>> +  }
>>
>>
> How temporary is this and do you plan on making the arguments
> non-schedulable? (Which is arguably what should be happening right? They
> should be the equivalent to an alloca yes?)
>

I already wrote code to replace it: http://reviews.llvm.org/D14750 . If
that patch isn't accepted, I'll go back to the drawing board to find some
other way to pin the instructions to the top of the block. I don't yet have
an idea for doing this, but it would be a high priority to find one.

Dan
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