[GlobalISel] Move isTriviallyDead to Utils. NFC.

Make it accessible by the targets to avoid code duplication.

llvm-svn: 298358

1 files changed, 0 insertions, 23 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp b/llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp
index c59b200298e..69ad59ade08 100644
--- a/llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp
@@ -48,29 +48,6 @@ void InstructionSelect::getAnalysisUsage(AnalysisUsage &AU) const {
   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();