[clang] [NFC] Factor out common parts of ArraySections into its own class (PR #89639)

[Alexey Bataev via cfe-commits]

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@@ -6610,6 +6610,111 @@ class TypoExpr : public Expr {
 
 };
 
+// This is a sub-class for OpenMP and OpenACC array sections. OpenACC uses a
+// very small subset of the functionality, so this class only exposes the things
+// the two have in common. This type is not expected to be used directly,
+// instead it is inherited from by the OMP and OpenACC variants.
+//
+// This type does not capture a 'stride', only a lower-bound and length (plus
+// the base expression), but provides room via a template argument to get
+// additional ones.
+template<unsigned NumSubExprs, bool AllowNullExprs>
+class ArraySectionExprBase : public Expr {
+  enum {BASE, LOWER_BOUND, LENGTH, END_EXPR = NumSubExprs};
+  Stmt *SubExprs[END_EXPR];
+  SourceLocation ColonLocFirst;
+  SourceLocation RBracketLoc;
+
+  protected:
+    ArraySectionExprBase(StmtClass SC, Expr *Base, Expr *LowerBound,
+                         Expr *Length, QualType Type, ExprValueKind VK,
+                         ExprObjectKind OK, SourceLocation ColonLocFirst,
+                         SourceLocation RBracketLoc)
+        : Expr(SC, Type, VK, OK), ColonLocFirst(ColonLocFirst),
+          RBracketLoc(RBracketLoc) {
+      setBase(Base);
+      setLowerBound(LowerBound);
+      setLength(Length);
+    }
+
+    explicit ArraySectionExprBase(StmtClass SC, EmptyShell Shell)
+        : Expr(SC, Shell) {}
+
+    void setSubExpr(unsigned Idx, Expr *SubExpr) {
+      assert(Idx > LENGTH &&
+             "setting sub expression owned by ArraySectionExprBase: Should be "
+             "using the direct 'setter' functions");
+      assert((SubExpr || AllowNullExprs) && "Null expression when not allowed");
+      SubExprs[Idx] = SubExpr;
+    }
+
+    Expr *getSubExpr(unsigned Idx) {
+      assert(Idx > LENGTH &&
+             "getting sub expression owned by ArraySectionExprBase: Should be "
+             "using the direct 'getter' functions");
+      return cast_or_null<Expr>(SubExprs[Idx]);
+    }
+    const Expr *getSubExpr(unsigned Idx) const {
+      assert(Idx > LENGTH &&
+             "getting sub expression owned by ArraySectionExprBase: Should be "
+             "using the direct 'getter' functions");
+      return cast_or_null<Expr>(SubExprs[Idx]);
+    }
+
+  public:
+  /// Get base of the array section.
+  Expr *getBase() { return cast<Expr>(SubExprs[BASE]); }
+  const Expr *getBase() const { return cast<Expr>(SubExprs[BASE]); }
+  /// Set base of the array section.
+  void setBase(Expr *E) {
+    assert((E || AllowNullExprs) && "Null expression when not allowed");
+    SubExprs[BASE] = E;
+  }
+
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alexey-bataev wrote:

Can you make it private or protected?

https://github.com/llvm/llvm-project/pull/89639