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