fixup! add TODO

Author: 4vtomat

llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp

@@ -895,10 +895,10 @@ bool RISCVRegisterInfo::getRegAllocationHints(
       // Check if this register matches the even/odd requirement
       bool IsOdd = (RegNum % 2 != 0);
 
-      // Skip unallocatable registers.
-      if (MRI->isReserved(PhysReg))
-        continue;
       // Verify the pair register exists and is in the same register class
+      // TODO: Skip unallocatable registers: we need to prevent any of odd/even
+      // to be reserved, so if we need odd, we need to check if corresponding
+      // even is preserved, vice versa.
       if ((WantOdd && IsOdd) || (!WantOdd && !IsOdd))
         Hints.push_back(PhysReg);
     }