C++: more UnreachedInstruction fixes

Author: Robert Marsh

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/IRConstruction.qll

@@ -180,7 +180,7 @@ module Raw {
 
 class TStageInstruction = TRawInstruction or TRawUnreachedInstruction;
 
-predicate hasInstruction(TRawInstruction instr) { any() }
+predicate hasInstruction(TStageInstruction instr) { any() }
 
 predicate hasModeledMemoryResult(Instruction instruction) { none() }
 
@@ -368,6 +368,11 @@ private predicate isStrictlyForwardGoto(GotoStmt goto) {
 
 Locatable getInstructionAst(TStageInstruction instr) {
   result = getInstructionTranslatedElement(instr).getAst()
+  or
+  exists(IRFunction irFunc |
+    instr = TRawUnreachedInstruction(irFunc) and
+    result = irFunc.getFunction()
+  )
 }
 
 /** DEPRECATED: Alias for getInstructionAst */
@@ -377,14 +382,22 @@ deprecated Locatable getInstructionAST(TStageInstruction instr) {
 
 CppType getInstructionResultType(TStageInstruction instr) {
   getInstructionTranslatedElement(instr).hasInstruction(_, getInstructionTag(instr), result)
+  or
+  instr instanceof TRawUnreachedInstruction and
+  result = getVoidType()
 }
 
 predicate getInstructionOpcode(Opcode opcode, TStageInstruction instr) {
   getInstructionTranslatedElement(instr).hasInstruction(opcode, getInstructionTag(instr), _)
+  or
+  instr instanceof TRawUnreachedInstruction and
+  opcode instanceof Opcode::Unreached
 }
 
 IRFunctionBase getInstructionEnclosingIRFunction(TStageInstruction instr) {
   result.getFunction() = getInstructionTranslatedElement(instr).getFunction()
+  or
+  instr = TRawUnreachedInstruction(result)
 }
 
 Instruction getPrimaryInstructionForSideEffect(SideEffectInstruction instruction) {