[llvm-commits] [llvm] r45620 - /llvm/trunk/lib/Target/X86/X86InstrInfo.cpp

[Chris Lattner]

On Jan 4, 2008, at 10:49 PM, Evan Cheng wrote:

>
> On Jan 4, 2008, at 9:19 PM, Chris Lattner wrote:
>
>> Author: lattner
>> Date: Fri Jan  4 23:19:56 2008
>> New Revision: 45620
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=45620&view=rev
>> Log:
>> factor some code better to avoid redundancy between
>> isReallySideEffectFree and isReallyTriviallyReMaterializable.  Why  
>> is a load from
>> a global considered side-effect-free but not rematable?
>
> No reason they should be different. I just haven't move remat over.

They really can't be right now, for a gross reason.  The issue is that  
"isrematable" always returns true except in a few cases.   
issideeffectfree returns false except in a few cases...

> Although, isReallySideEffectFree looks wrong. How is this checked?

I agree, this looks bogus or scary to me.

-Chris

>
>
>      // Loads from global addresses which aren't redefined in the  
> function are
>     // side effect free.
> if (Reg != 0 && MRegisterInfo::isVirtualRegister(Reg) &&
>          MI->getOperand(2).isImmediate() &&
>          MI->getOperand(3).isRegister() &&
>          MI->getOperand(4).isGlobalAddress() &&
>          MI->getOperand(2).getImm() == 1 &&
>          MI->getOperand(3).getReg() == 0)
>        return true;
>
> Bill, how are you checking the Global address isn't redefined  
> anywhere else?
>
> Evan
>
>>
>> Modified:
>>    llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
>>
>> Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=45620&r1=45619&r2=45620&view=diff
>>
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> =====================================================================
>> --- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
>> +++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Fri Jan  4 23:19:56  
>> 2008
>> @@ -135,11 +135,13 @@
>>   case X86::MMX_MOVD64rm:
>>   case X86::MMX_MOVQ64rm:
>>     // Loads from constant pools are trivially rematerializable.
>> -    return MI->getOperand(1).isRegister() && MI- 
>> >getOperand(2).isImmediate() &&
>> -           MI->getOperand(3).isRegister() && MI- 
>> >getOperand(4).isConstantPoolIndex() &&
>> -           MI->getOperand(1).getReg() == 0 &&
>> -           MI->getOperand(2).getImm() == 1 &&
>> -           MI->getOperand(3).getReg() == 0;
>> +    if (MI->getOperand(1).isReg() && MI->getOperand(2).isImm() &&
>> +        MI->getOperand(3).isReg() && MI->getOperand(4).isCPI() &&
>> +        MI->getOperand(1).getReg() == 0 &&
>> +        MI->getOperand(2).getImm() == 1 &&
>> +        MI->getOperand(3).getReg() == 0)
>> +      return true;
>> +    return false;
>>   }
>>   // All other instructions marked M_REMATERIALIZABLE are always  
>> trivially
>>   // rematerializable.
>> @@ -168,32 +170,11 @@
>>           MI->getOperand(3).getReg() == 0)
>>         return true;
>>     }
>> -    // FALLTHROUGH
>> -  case X86::MOV8rm:
>> -  case X86::MOV16rm:
>> -  case X86::MOV16_rm:
>> -  case X86::MOV32_rm:
>> -  case X86::MOV64rm:
>> -  case X86::LD_Fp64m:
>> -  case X86::MOVSSrm:
>> -  case X86::MOVSDrm:
>> -  case X86::MOVAPSrm:
>> -  case X86::MOVAPDrm:
>> -  case X86::MMX_MOVD64rm:
>> -  case X86::MMX_MOVQ64rm:
>> -    // Loads from constant pools have no side effects
>> -    return MI->getOperand(1).isRegister() &&
>> -           MI->getOperand(2).isImmediate() &&
>> -           MI->getOperand(3).isRegister() &&
>> -           MI->getOperand(4).isConstantPoolIndex() &&
>> -           MI->getOperand(1).getReg() == 0 &&
>> -           MI->getOperand(2).getImm() == 1 &&
>> -           MI->getOperand(3).getReg() == 0;
>> +    break;
>>   }
>>
>> -  // All other instances of these instructions are presumed to  
>> have side
>> -  // effects.
>> -  return false;
>> +  // Anything that is rematerializable obviously has no side  
>> effects.
>> +  return isReallyTriviallyReMaterializable(MI);
>> }
>>
>> /// hasLiveCondCodeDef - True if MI has a condition code def, e.g.  
>> EFLAGS, that
>>
>>
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