[BranchRelaxation] Move faulting_op check into callee [nfc]

Mostly to remove a special case from an upcoming patch.

Author: preames

llvm/lib/CodeGen/BranchRelaxation.cpp

@@ -284,6 +284,12 @@ MachineBasicBlock *BranchRelaxation::splitBlockBeforeInstr(MachineInstr &MI,
 /// specific BB can fit in MI's displacement field.
 bool BranchRelaxation::isBlockInRange(
   const MachineInstr &MI, const MachineBasicBlock &DestBB) const {
+
+  // FAULTING_OP's destination is not encoded in the instruction stream
+  // and thus always in range.
+  if (MI.getOpcode() == TargetOpcode::FAULTING_OP)
+    return true;
+
   int64_t BrOffset = getInstrOffset(MI);
   int64_t DestOffset = BlockInfo[DestBB.getNumber()].Offset;
 
@@ -558,11 +564,6 @@ bool BranchRelaxation::relaxBranchInstructions() {
       if (!MI.isConditionalBranch())
         continue;
 
-      if (MI.getOpcode() == TargetOpcode::FAULTING_OP)
-        // FAULTING_OP's destination is not encoded in the instruction stream
-        // and thus never needs relaxed.
-        continue;
-
       MachineBasicBlock *DestBB = TII->getBranchDestBlock(MI);
       if (!isBlockInRange(MI, *DestBB)) {
         if (Next != MBB.end() && Next->isConditionalBranch()) {