Corrected some typos found in MachineSink.cpp

[hudsontek]

Summary

Corrected some typo in llvm/lib/CodeGen/MachineSink.cpp

[MatzeB]

LGTM

llvm/lib/CodeGen/MachineSink.cpp

private:
     /// False can be returned if, for instance, this is not profitable.
     bool PostponeSplitCriticalEdge(MachineInstr &MI,
                                    MachineBasicBlock *From,
                                    MachineBasicBlock *To,
                                    bool BreakPHIEdge);
     bool SinkInstruction(MachineInstr &MI, bool &SawStore,
                          AllSuccsCache &AllSuccessors);
 
-    /// If we sink a COPY inst, some debug users of it's destination may no
+    /// If we sink a COPY inst, some debug users of its destination may no
     /// longer be dominated by the COPY, and will eventually be dropped.
     /// This is easily rectified by forwarding the non-dominated debug uses
     /// to the copy source.
     void SalvageUnsunkDebugUsersOfCopy(MachineInstr &,
                                        MachineBasicBlock *TargetBlock);
     bool AllUsesDominatedByBlock(Register Reg, MachineBasicBlock *MBB,
                                  MachineBasicBlock *DefMBB, bool &BreakPHIEdge,
                                  bool &LocalUse) const;
bool MachineSinking::AllUsesDominatedByBlock(Register Reg,
                                              bool &BreakPHIEdge,
                                              bool &LocalUse) const {
   assert(Register::isVirtualRegister(Reg) && "Only makes sense for vregs");
 
   // Ignore debug uses because debug info doesn't affect the code.
   if (MRI->use_nodbg_empty(Reg))
     return true;
 
-  // BreakPHIEdge is true if all the uses are in the successor MBB being sunken
+  // BreakPHIEdge is true if all the uses are in the successor MBB being sunk
   // into and they are all PHI nodes. In this case, machine-sink must break
   // the critical edge first. e.g.
   //
   // %bb.1:
   //   Predecessors according to CFG: %bb.0
   //     ...
   //     %def = DEC64_32r %x, implicit-def dead %eflags
   //     ...