Merge pull request #13907 from MathiasVP/cleanup-ssa-internals

C++: Small cleanup of `SsaInternals`

Author: Robert Marsh

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll

@@ -1078,7 +1078,7 @@ private IRVariable getIRVariableForParameterNode(ParameterNode p) {
 
 /** Holds if `v` is the source variable corresponding to the parameter represented by `p`. */
 pragma[nomagic]
-private predicate parameterNodeHasSourceVariable(ParameterNode p, Ssa::SourceIRVariable v) {
+private predicate parameterNodeHasSourceVariable(ParameterNode p, Ssa::SourceVariable v) {
   v.getIRVariable() = getIRVariableForParameterNode(p) and
   exists(Position pos | p.isParameterOf(_, pos) |
     pos instanceof DirectPosition and

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaInternals.qll

@@ -10,98 +10,55 @@ private import ssa0.SsaInternals as SsaInternals0
 import SsaInternalsCommon
 
 private module SourceVariables {
-  int getMaxIndirectionForIRVariable(IRVariable var) {
-    exists(Type type, boolean isGLValue |
-      var.getLanguageType().hasType(type, isGLValue) and
-      if isGLValue = true
-      then result = 1 + getMaxIndirectionsForType(type)
-      else result = getMaxIndirectionsForType(type)
-    )
-  }
-
   cached
   private newtype TSourceVariable =
-    TSourceIRVariable(BaseIRVariable baseVar, int ind) {
-      ind = [0 .. getMaxIndirectionForIRVariable(baseVar.getIRVariable())]
-    } or
-    TCallVariable(AllocationInstruction call, int ind) {
-      ind = [0 .. countIndirectionsForCppType(getResultLanguageType(call))]
+    TMkSourceVariable(SsaInternals0::SourceVariable base, int ind) {
+      ind = [0 .. countIndirectionsForCppType(base.getLanguageType()) + 1]
     }
 
-  abstract class SourceVariable extends TSourceVariable {
+  class SourceVariable extends TSourceVariable {
+    SsaInternals0::SourceVariable base;
     int ind;
 
-    bindingset[ind]
-    SourceVariable() { any() }
+    SourceVariable() { this = TMkSourceVariable(base, ind) }
+
+    /** Gets the IR variable associated with this `SourceVariable`, if any. */
+    IRVariable getIRVariable() { result = base.(BaseIRVariable).getIRVariable() }
+
+    /**
+     * Gets the base source variable (i.e., the variable without any
+     * indirections) of this source variable.
+     */
+    SsaInternals0::SourceVariable getBaseVariable() { result = base }
 
     /** Gets a textual representation of this element. */
-    abstract string toString();
+    string toString() {
+      ind = 0 and
+      result = this.getBaseVariable().toString()
+      or
+      ind > 0 and
+      result = this.getBaseVariable().toString() + " indirection"
+    }
 
     /**
      * Gets the number of loads performed on the base source variable
      * to reach the value of this source variable.
      */
     int getIndirection() { result = ind }
 
-    /**
-     * Gets the base source variable (i.e., the variable without any
-     * indirections) of this source variable.
-     */
-    abstract BaseSourceVariable getBaseVariable();
-
     /** Holds if this variable is a glvalue. */
-    predicate isGLValue() { none() }
+    predicate isGLValue() { ind = 0 }
 
     /**
      * Gets the type of this source variable. If `isGLValue()` holds, then
      * the type of this source variable should be thought of as "pointer
      * to `getType()`".
      */
-    abstract DataFlowType getType();
-  }
-
-  class SourceIRVariable extends SourceVariable, TSourceIRVariable {
-    BaseIRVariable var;
-
-    SourceIRVariable() { this = TSourceIRVariable(var, ind) }
-
-    IRVariable getIRVariable() { result = var.getIRVariable() }
-
-    override BaseIRVariable getBaseVariable() { result.getIRVariable() = this.getIRVariable() }
-
-    override string toString() {
-      ind = 0 and
-      result = this.getIRVariable().toString()
-      or
-      ind > 0 and
-      result = this.getIRVariable().toString() + " indirection"
-    }
-
-    override predicate isGLValue() { ind = 0 }
-
-    override DataFlowType getType() {
-      if ind = 0 then result = var.getType() else result = getTypeImpl(var.getType(), ind - 1)
-    }
-  }
-
-  class CallVariable extends SourceVariable, TCallVariable {
-    AllocationInstruction call;
-
-    CallVariable() { this = TCallVariable(call, ind) }
-
-    AllocationInstruction getCall() { result = call }
-
-    override BaseCallVariable getBaseVariable() { result.getCallInstruction() = call }
-
-    override string toString() {
-      ind = 0 and
-      result = "Call"
-      or
-      ind > 0 and
-      result = "Call indirection"
+    DataFlowType getType() {
+      if this.isGLValue()
+      then result = base.getType()
+      else result = getTypeImpl(base.getType(), ind - 1)
     }
-
-    override DataFlowType getType() { result = getTypeImpl(call.getResultType(), ind) }
   }
 }
 

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaInternalsCommon.qll

@@ -370,15 +370,20 @@ newtype TBaseSourceVariable =
   // Each allocation gets its own source variable
   TBaseCallVariable(AllocationInstruction call)
 
-abstract class BaseSourceVariable extends TBaseSourceVariable {
+abstract private class AbstractBaseSourceVariable extends TBaseSourceVariable {
   /** Gets a textual representation of this element. */
   abstract string toString();
 
   /** Gets the type of this base source variable. */
-  abstract DataFlowType getType();
+  final DataFlowType getType() { this.getLanguageType().hasUnspecifiedType(result, _) }
+
+  /** Gets the `CppType` of this base source variable. */
+  abstract CppType getLanguageType();
 }
 
-class BaseIRVariable extends BaseSourceVariable, TBaseIRVariable {
+final class BaseSourceVariable = AbstractBaseSourceVariable;
+
+class BaseIRVariable extends AbstractBaseSourceVariable, TBaseIRVariable {
   IRVariable var;
 
   IRVariable getIRVariable() { result = var }
@@ -387,10 +392,10 @@ class BaseIRVariable extends BaseSourceVariable, TBaseIRVariable {
 
   override string toString() { result = var.toString() }
 
-  override DataFlowType getType() { result = var.getType() }
+  override CppType getLanguageType() { result = var.getLanguageType() }
 }
 
-class BaseCallVariable extends BaseSourceVariable, TBaseCallVariable {
+class BaseCallVariable extends AbstractBaseSourceVariable, TBaseCallVariable {
   AllocationInstruction call;
 
   BaseCallVariable() { this = TBaseCallVariable(call) }
@@ -399,7 +404,7 @@ class BaseCallVariable extends BaseSourceVariable, TBaseCallVariable {
 
   override string toString() { result = call.toString() }
 
-  override DataFlowType getType() { result = call.getResultType() }
+  override CppType getLanguageType() { result = getResultLanguageType(call) }
 }
 
 /**

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/ssa0/SsaInternals.qll

@@ -15,15 +15,12 @@ private import semmle.code.cpp.ir.dataflow.internal.DataFlowUtil
 private import semmle.code.cpp.ir.dataflow.internal.SsaInternalsCommon
 
 private module SourceVariables {
-  class SourceVariable instanceof BaseSourceVariable {
-    string toString() { result = BaseSourceVariable.super.toString() }
-
+  class SourceVariable extends BaseSourceVariable {
+    /**
+     * Gets the base source variable of this `SourceVariable`.
+     */
     BaseSourceVariable getBaseVariable() { result = this }
   }
-
-  class SourceIRVariable = BaseIRVariable;
-
-  class CallVariable = BaseCallVariable;
 }
 
 import SourceVariables