C++: Add Arm scalable vector type QL classes

Author: jketema

cpp/ql/lib/semmle/code/cpp/Type.qll

@@ -355,6 +355,15 @@ private predicate isArithmeticType(@builtintype type, int kind) {
   kind != 34 // Exclude decltype(nullptr)
 }
 
+/**
+ * The Arm scalable vector count type `__SVCount_t`.
+ */
+class ScalableVectorCount extends BuiltInType {
+  ScalableVectorCount() { builtintypes(underlyingElement(this), _, 63, _, _, _) }
+
+  override string getAPrimaryQlClass() { result = "ScalableVectorCount" }
+}
+
 /**
  * The C/C++ arithmetic types. See 4.1.1.
  *
@@ -1084,7 +1093,7 @@ class NullPointerType extends BuiltInType {
 /**
  * A C/C++ derived type.
  *
- * These are pointer and reference types, array and GNU vector types, and `const` and `volatile` types.
+ * These are pointer and reference types, array and vector types, and `const` and `volatile` types.
  * In all cases, the type is formed from a single base type.  For example:
  * ```
  * int *pi;
@@ -1643,6 +1652,26 @@ class GNUVectorType extends DerivedType {
   override predicate isDeeplyConstBelow() { this.getBaseType().isDeeplyConst() }
 }
 
+/**
+ * An Arm Scalable vector type.
+ */
+class ScalableVectorType extends DerivedType {
+  ScalableVectorType() { derivedtypes(underlyingElement(this), _, 11, _) }
+
+  /**
+   * Get the number of tuple elements of this scalable vector type.
+   */
+  int getNumTupleElements() { tupleelements(underlyingElement(this), result) }
+
+  override string getAPrimaryQlClass() { result = "ScalableVectorType" }
+
+  override int getAlignment() { arraysizes(underlyingElement(this), _, _, result) }
+
+  override string explain() { result = "scalable vector of {" + this.getBaseType().explain() + "}" }
+
+  override predicate isDeeplyConstBelow() { this.getBaseType().isDeeplyConst() }
+}
+
 /**
  * A C/C++ pointer to a function. See 7.7.
  * ```

cpp/ql/lib/semmlecode.cpp.dbscheme

@@ -692,6 +692,7 @@ case @builtintype.kind of
 | 60 = @complex_float64x      // _Complex _Float64x
 | 61 = @complex_std_float128  // _Complex _Float128
 | 62 = @mfp8                  // __mfp8
+| 63 = @scalable_vector_count
 ;
 
 builtintypes(
@@ -718,6 +719,7 @@ case @derivedtype.kind of
 |  8 = @rvalue_reference // C++11
 // ... 9 type_conforming_to_protocols deprecated
 | 10 = @block
+| 11 = @scalable_vector // Arm SVE
 ;
 
 derivedtypes(
@@ -738,6 +740,11 @@ arraysizes(
     int alignment: int ref
 );
 
+tupleelements(
+    unique int id: @derivedtype ref,
+    int num_elements: int ref
+);
+
 typedefbase(
     unique int id: @usertype ref,
     int type_id: @type ref