C++ IR: make isInCycle fast

Without this `pragma[noopt]`, `isInCycle` gets compiled into RA that
unpacks every tuple of the fast TC:

                      0          ~0%     {2} r1 = SELECT #Operand::getNonPhiOperandDef#3#ffPlus ON FIELDS #Operand::getNonPhiOperandDef#3#ffPlus.<0>=#Operand::getNonPhiOperandDef#3#ffPlus.<1>
                      0          ~0%     {1} r2 = SCAN r1 OUTPUT FIELDS {r1.<0>}
                                         return r2

With this change, it just becomes one lookup in the fast TC data
structure per instruction.

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Operand.qll

@@ -35,7 +35,9 @@ private Instruction getNonPhiOperandDef(Instruction instr) {
  * analyses that assume a cycle-free graph of non-phi operands. Therefore it's
  * better to remove these operands than to leave cycles in the operand graph.
  */
+pragma[noopt]
 private predicate isInCycle(Instruction instr) {
+  instr instanceof Instruction and
   getNonPhiOperandDef+(instr) = instr
 }
 

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Operand.qll

@@ -35,7 +35,9 @@ private Instruction getNonPhiOperandDef(Instruction instr) {
  * analyses that assume a cycle-free graph of non-phi operands. Therefore it's
  * better to remove these operands than to leave cycles in the operand graph.
  */
+pragma[noopt]
 private predicate isInCycle(Instruction instr) {
+  instr instanceof Instruction and
   getNonPhiOperandDef+(instr) = instr
 }
 

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Operand.qll

@@ -35,7 +35,9 @@ private Instruction getNonPhiOperandDef(Instruction instr) {
  * analyses that assume a cycle-free graph of non-phi operands. Therefore it's
  * better to remove these operands than to leave cycles in the operand graph.
  */
+pragma[noopt]
 private predicate isInCycle(Instruction instr) {
+  instr instanceof Instruction and
   getNonPhiOperandDef+(instr) = instr
 }