C++: Don't have ReachableBlock extends IRBlock

Author: dave-bartolomeo

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

@@ -3,7 +3,18 @@ import Instruction
 import semmle.code.cpp.ir.implementation.EdgeKind
 private import Cached
 
-class IRBlock extends TIRBlock {
+/**
+ * A basic block in the IR. A basic block consists of a sequence of `Instructions` with the only
+ * incoming edges at the beginning of the sequence and the only outgoing edges at the end of the
+ * sequence.
+ *
+ * This class does not contain any members that query the predecessor or successor edges of the
+ * block. This allows different classes that extend `IRBlockBase` to expose different subsets of
+ * edges (e.g. ignoring unreachable edges).
+ *
+ * Most consumers should use the class `IRBlock`.
+ */
+class IRBlockBase extends TIRBlock {
   final string toString() {
     result = getFirstInstruction(this).toString()
   }
@@ -59,7 +70,14 @@ class IRBlock extends TIRBlock {
   final Function getFunction() {
     result = getFirstInstruction(this).getFunction()
   }
+}
 
+/**
+ * A basic block with additional information about its predecessor and successor edges. Each edge
+ * corresponds to the control flow between the last instruction of one block and the first
+ * instruction of another block.
+ */
+class IRBlock extends IRBlockBase {
   final IRBlock getASuccessor() {
     blockSuccessor(this, result)
   }

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

@@ -3,7 +3,18 @@ import Instruction
 import semmle.code.cpp.ir.implementation.EdgeKind
 private import Cached
 
-class IRBlock extends TIRBlock {
+/**
+ * A basic block in the IR. A basic block consists of a sequence of `Instructions` with the only
+ * incoming edges at the beginning of the sequence and the only outgoing edges at the end of the
+ * sequence.
+ *
+ * This class does not contain any members that query the predecessor or successor edges of the
+ * block. This allows different classes that extend `IRBlockBase` to expose different subsets of
+ * edges (e.g. ignoring unreachable edges).
+ *
+ * Most consumers should use the class `IRBlock`.
+ */
+class IRBlockBase extends TIRBlock {
   final string toString() {
     result = getFirstInstruction(this).toString()
   }
@@ -59,7 +70,14 @@ class IRBlock extends TIRBlock {
   final Function getFunction() {
     result = getFirstInstruction(this).getFunction()
   }
+}
 
+/**
+ * A basic block with additional information about its predecessor and successor edges. Each edge
+ * corresponds to the control flow between the last instruction of one block and the first
+ * instruction of another block.
+ */
+class IRBlock extends IRBlockBase {
   final IRBlock getASuccessor() {
     blockSuccessor(this, result)
   }

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/reachability/ReachableBlock.qll

@@ -13,28 +13,28 @@ predicate isInfeasibleInstructionSuccessor(Instruction instr, EdgeKind kind) {
   )
 }
 
-predicate isInfeasibleEdge(IRBlock block, EdgeKind kind) {
+predicate isInfeasibleEdge(IRBlockBase block, EdgeKind kind) {
   isInfeasibleInstructionSuccessor(block.getLastInstruction(), kind)
 }
 
-IRBlock getAFeasiblePredecessorBlock(IRBlock successor) {
+private IRBlock getAFeasiblePredecessorBlock(IRBlock successor) {
   exists(EdgeKind kind |
     result.getSuccessor(kind) = successor and
     not isInfeasibleEdge(result, kind)
   )
 }
 
-predicate isBlockReachable(IRBlock block) {
+private predicate isBlockReachable(IRBlock block) {
   exists(FunctionIR f |
     getAFeasiblePredecessorBlock*(block) = f.getEntryBlock()
   )
 }
 
-predicate isInstructionReachable(Instruction instr) {
-  isBlockReachable(instr.getBlock())
-}
-
-class ReachableBlock extends IRBlock {
+/**
+ * An IR block that is reachable from the entry block of the function, considering only feasible
+ * edges.
+ */
+class ReachableBlock extends IRBlockBase {
   ReachableBlock() {
     isBlockReachable(this)
   }
@@ -48,6 +48,9 @@ class ReachableBlock extends IRBlock {
   }
 }
 
+/**
+ * An instruction that is contained in a reachable block.
+ */
 class ReachableInstruction extends Instruction {
   ReachableInstruction() {
     this.getBlock() instanceof ReachableBlock

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

@@ -3,7 +3,18 @@ import Instruction
 import semmle.code.cpp.ir.implementation.EdgeKind
 private import Cached
 
-class IRBlock extends TIRBlock {
+/**
+ * A basic block in the IR. A basic block consists of a sequence of `Instructions` with the only
+ * incoming edges at the beginning of the sequence and the only outgoing edges at the end of the
+ * sequence.
+ *
+ * This class does not contain any members that query the predecessor or successor edges of the
+ * block. This allows different classes that extend `IRBlockBase` to expose different subsets of
+ * edges (e.g. ignoring unreachable edges).
+ *
+ * Most consumers should use the class `IRBlock`.
+ */
+class IRBlockBase extends TIRBlock {
   final string toString() {
     result = getFirstInstruction(this).toString()
   }
@@ -59,7 +70,14 @@ class IRBlock extends TIRBlock {
   final Function getFunction() {
     result = getFirstInstruction(this).getFunction()
   }
+}
 
+/**
+ * A basic block with additional information about its predecessor and successor edges. Each edge
+ * corresponds to the control flow between the last instruction of one block and the first
+ * instruction of another block.
+ */
+class IRBlock extends IRBlockBase {
   final IRBlock getASuccessor() {
     blockSuccessor(this, result)
   }

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/reachability/ReachableBlock.qll

@@ -13,28 +13,28 @@ predicate isInfeasibleInstructionSuccessor(Instruction instr, EdgeKind kind) {
   )
 }
 
-predicate isInfeasibleEdge(IRBlock block, EdgeKind kind) {
+predicate isInfeasibleEdge(IRBlockBase block, EdgeKind kind) {
   isInfeasibleInstructionSuccessor(block.getLastInstruction(), kind)
 }
 
-IRBlock getAFeasiblePredecessorBlock(IRBlock successor) {
+private IRBlock getAFeasiblePredecessorBlock(IRBlock successor) {
   exists(EdgeKind kind |
     result.getSuccessor(kind) = successor and
     not isInfeasibleEdge(result, kind)
   )
 }
 
-predicate isBlockReachable(IRBlock block) {
+private predicate isBlockReachable(IRBlock block) {
   exists(FunctionIR f |
     getAFeasiblePredecessorBlock*(block) = f.getEntryBlock()
   )
 }
 
-predicate isInstructionReachable(Instruction instr) {
-  isBlockReachable(instr.getBlock())
-}
-
-class ReachableBlock extends IRBlock {
+/**
+ * An IR block that is reachable from the entry block of the function, considering only feasible
+ * edges.
+ */
+class ReachableBlock extends IRBlockBase {
   ReachableBlock() {
     isBlockReachable(this)
   }
@@ -48,6 +48,9 @@ class ReachableBlock extends IRBlock {
   }
 }
 
+/**
+ * An instruction that is contained in a reachable block.
+ */
 class ReachableInstruction extends Instruction {
   ReachableInstruction() {
     this.getBlock() instanceof ReachableBlock