[llvm] r298358 - [GlobalISel] Move isTriviallyDead to Utils. NFC.

[Quentin Colombet via llvm-commits]

Hi Volkan and Ahmed,

> On Mar 21, 2017, at 3:47 AM, Volkan Keles via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> Author: volkan
> Date: Tue Mar 21 05:47:35 2017
> New Revision: 298358
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=298358&view=rev
> Log:
> [GlobalISel] Move isTriviallyDead to Utils. NFC.
> 
> Make it accessible by the targets to avoid code duplication.
> 
> Modified:
>    llvm/trunk/include/llvm/CodeGen/GlobalISel/Utils.h
>    llvm/trunk/lib/CodeGen/GlobalISel/InstructionSelect.cpp
>    llvm/trunk/lib/CodeGen/GlobalISel/Utils.cpp
> 
> Modified: llvm/trunk/include/llvm/CodeGen/GlobalISel/Utils.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/GlobalISel/Utils.h?rev=298358&r1=298357&r2=298358&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/CodeGen/GlobalISel/Utils.h (original)
> +++ llvm/trunk/include/llvm/CodeGen/GlobalISel/Utils.h Tue Mar 21 05:47:35 2017
> @@ -45,6 +45,10 @@ unsigned constrainOperandRegClass(const
>                                   MachineInstr &InsertPt, const MCInstrDesc &II,
>                                   unsigned Reg, unsigned OpIdx);
> 
> +/// Check whether an instruction \p MI is dead: it only defines dead virtual
> +/// registers, and doesn't have other side effects.
> +bool isTriviallyDead(const MachineInstr &MI, const MachineRegisterInfo &MRI);
> +
> /// Report an ISel error as a missed optimization remark to the LLVMContext's
> /// diagnostic stream.  Set the FailedISel MachineFunction property.
> void reportGISelFailure(MachineFunction &MF, const TargetPassConfig &TPC,
> 
> Modified: llvm/trunk/lib/CodeGen/GlobalISel/InstructionSelect.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/GlobalISel/InstructionSelect.cpp?rev=298358&r1=298357&r2=298358&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/GlobalISel/InstructionSelect.cpp (original)
> +++ llvm/trunk/lib/CodeGen/GlobalISel/InstructionSelect.cpp Tue Mar 21 05:47:35 2017
> @@ -48,29 +48,6 @@ void InstructionSelect::getAnalysisUsage
>   MachineFunctionPass::getAnalysisUsage(AU);
> }
> 
> -/// Check whether an instruction \p MI is dead: it only defines dead virtual
> -/// registers, and doesn't have other side effects.
> -static bool isTriviallyDead(const MachineInstr &MI,
> -                            const MachineRegisterInfo &MRI) {
> -  // If we can move an instruction, we can remove it.  Otherwise, it has
> -  // a side-effect of some sort.
> -  bool SawStore = false;
> -  if (!MI.isSafeToMove(/*AA=*/nullptr, SawStore))
> -    return false;
> -
> -  // Instructions without side-effects are dead iff they only define dead vregs.
> -  for (auto &MO : MI.operands()) {
> -    if (!MO.isReg() || !MO.isDef())
> -      continue;
> -
> -    unsigned Reg = MO.getReg();
> -    // Keep Debug uses live: we don't want to have an effect on debug info.
> -    if (TargetRegisterInfo::isPhysicalRegister(Reg) || !MRI.use_empty(Reg))
> -      return false;
> -  }
> -  return true;
> -}
> -
> bool InstructionSelect::runOnMachineFunction(MachineFunction &MF) {
>   const MachineRegisterInfo &MRI = MF.getRegInfo();
> 
> 
> Modified: llvm/trunk/lib/CodeGen/GlobalISel/Utils.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/GlobalISel/Utils.cpp?rev=298358&r1=298357&r2=298358&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/GlobalISel/Utils.cpp (original)
> +++ llvm/trunk/lib/CodeGen/GlobalISel/Utils.cpp Tue Mar 21 05:47:35 2017
> @@ -47,6 +47,27 @@ unsigned llvm::constrainOperandRegClass(
>   return Reg;
> }
> 
> +bool llvm::isTriviallyDead(const MachineInstr &MI,
> +                           const MachineRegisterInfo &MRI) {
> +  // If we can move an instruction, we can remove it.  Otherwise, it has
> +  // a side-effect of some sort.
> +  bool SawStore = false;
> +  if (!MI.isSafeToMove(/*AA=*/nullptr, SawStore))
> +    return false;
> +
> +  // Instructions without side-effects are dead iff they only define dead vregs.
> +  for (auto &MO : MI.operands()) {
> +    if (!MO.isReg() || !MO.isDef())
> +      continue;
> +
> +    unsigned Reg = MO.getReg();
> +    // Keep Debug uses live: we don't want to have an effect on debug info.

I’m actually wondering about that one.
Debug information is not supposed to alter codegen.

WDTY?

Cheers,
-Quentin

> +    if (TargetRegisterInfo::isPhysicalRegister(Reg) || !MRI.use_empty(Reg))
> +      return false;
> +  }
> +  return true;
> +}
> +
> void llvm::reportGISelFailure(MachineFunction &MF, const TargetPassConfig &TPC,
>                               MachineOptimizationRemarkEmitter &MORE,
>                               MachineOptimizationRemarkMissed &R) {
> 
> 
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