[NFC][Clang] Add helper functions/utils for finding/comparing attach base-ptrs.

These have been pulled out of the codegen PR #153683, to reduce the size
of that PR.

Author: abhinavgaba

clang/include/clang/AST/OpenMPClause.h

@@ -5815,6 +5815,12 @@ class OMPClauseMappableExprCommon {
     ValueDecl *getAssociatedDeclaration() const {
       return AssociatedDeclaration;
     }
+
+    bool operator==(const MappableComponent &Other) const {
+      return AssociatedExpressionNonContiguousPr ==
+                 Other.AssociatedExpressionNonContiguousPr &&
+             AssociatedDeclaration == Other.AssociatedDeclaration;
+    }
   };
 
   // List of components of an expression. This first one is the whole
@@ -5828,6 +5834,95 @@ class OMPClauseMappableExprCommon {
   using MappableExprComponentLists = SmallVector<MappableExprComponentList, 8>;
   using MappableExprComponentListsRef = ArrayRef<MappableExprComponentList>;
 
+  // Hash function to allow usage as DenseMap keys.
+  friend llvm::hash_code hash_value(const MappableComponent &MC) {
+    return llvm::hash_combine(MC.getAssociatedExpression(),
+                              MC.getAssociatedDeclaration(),
+                              MC.isNonContiguous());
+  }
+
+public:
+  /// Get the type of an element of a ComponentList Expr \p Exp.
+  ///
+  /// For something like the following:
+  /// ```c
+  ///  int *p, **p;
+  /// ```
+  /// The types for the following Exprs would be:
+  ///   Expr     | Type
+  ///   ---------|-----------
+  ///   p        | int *
+  ///   *p       | int
+  ///   p[0]     | int
+  ///   p[0:1]   | int
+  ///   pp       | int **
+  ///   pp[0]    | int *
+  ///   pp[0:1]  | int *
+  /// Note: this assumes that if \p Exp is an array-section, it is contiguous.
+  static QualType getComponentExprElementType(const Expr *Exp);
+
+  /// Find the attach pointer expression from a list of mappable expression
+  /// components.
+  ///
+  /// This function traverses the component list to find the first
+  /// expression that has a pointer type, which represents the attach
+  /// base pointer expr for the current component-list.
+  ///
+  /// For example, given the following:
+  ///
+  /// ```c
+  ///   struct S {
+  ///     int a;
+  ///     int b[10];
+  ///     int c[10][10];
+  ///     int *p;
+  ///     int **pp;
+  ///   }
+  ///   S s, *ps, **pps, *(pas[10]), ***ppps;
+  ///   int i;
+  /// ```
+  ///
+  /// The base-pointers for the following map operands would be:
+  ///   map list-item   | attach base-pointer   | attach base-pointer
+  ///                   | for directives except | target_update (if
+  ///                   | target_update         | different)
+  ///   ----------------|-----------------------|---------------------
+  ///   s               | N/A                   |
+  ///   s.a             | N/A                   |
+  ///   s.p             | N/A                   |
+  ///   ps              | N/A                   |
+  ///   ps->p           | ps                    |
+  ///   ps[1]           | ps                    |
+  ///   *(ps + 1)       | ps                    |
+  ///   (ps + 1)[1]     | ps                    |
+  ///   ps[1:10]        | ps                    |
+  ///   ps->b[10]       | ps                    |
+  ///   ps->p[10]       | ps->p                 |
+  ///   ps->c[1][2]     | ps                    |
+  ///   ps->c[1:2][2]   | (error diagnostic)    | N/A, TODO: ps
+  ///   ps->c[1:1][2]   | ps                    | N/A, TODO: ps
+  ///   pps[1][2]       | pps[1]                |
+  ///   pps[1:1][2]     | pps[1:1]              | N/A, TODO: pps[1:1]
+  ///   pps[1:i][2]     | pps[1:i]              | N/A, TODO: pps[1:i]
+  ///   pps[1:2][2]     | (error diagnostic)    | N/A
+  ///   pps[1]->p       | pps[1]                |
+  ///   pps[1]->p[10]   | pps[1]                |
+  ///   pas[1]          | N/A                   |
+  ///   pas[1][2]       | pas[1]                |
+  ///   ppps[1][2]      | ppps[1]               |
+  ///   ppps[1][2][3]   | ppps[1][2]            |
+  ///   ppps[1][2:1][3] | ppps[1][2:1]          | N/A, TODO: ppps[1][2:1]
+  ///   ppps[1][2:2][3] | (error diagnostic)    | N/A
+  /// Returns a pair of the attach pointer expression and its depth in the
+  /// component list.
+  /// TODO: This may need to be updated to handle ref_ptr/ptee cases for byref
+  /// map operands.
+  /// TODO: Handle cases for target-update, where the list-item is a
+  /// non-contiguous array-section that still has a base-pointer.
+  static std::pair<const Expr *, std::optional<size_t>>
+  findAttachPtrExpr(MappableExprComponentListRef Components,
+                    OpenMPDirectiveKind CurDirKind);
+
 protected:
   // Return the total number of elements in a list of component lists.
   static unsigned

clang/include/clang/Basic/OpenMPKinds.h

@@ -301,6 +301,14 @@ bool isOpenMPTargetExecutionDirective(OpenMPDirectiveKind DKind);
 /// otherwise - false.
 bool isOpenMPTargetDataManagementDirective(OpenMPDirectiveKind DKind);
 
+/// Checks if the specified directive is a map-entering target directive.
+/// \param DKind Specified directive.
+/// \return true - the directive is a map-entering target directive like
+/// 'omp target', 'omp target data', 'omp target enter data',
+/// 'omp target parallel', etc. (excludes 'omp target exit data', 'omp target
+/// update') otherwise - false.
+bool isOpenMPTargetMapEnteringDirective(OpenMPDirectiveKind DKind);
+
 /// Checks if the specified composite/combined directive constitutes a teams
 /// directive in the outermost nest.  For example
 /// 'omp teams distribute' or 'omp teams distribute parallel for'.

clang/lib/AST/OpenMPClause.cpp

@@ -15,6 +15,7 @@
 #include "clang/AST/Attr.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclOpenMP.h"
+#include "clang/AST/ExprOpenMP.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/OpenMPKinds.h"
 #include "clang/Basic/TargetInfo.h"
@@ -1156,6 +1157,73 @@ unsigned OMPClauseMappableExprCommon::getUniqueDeclarationsTotalNumber(
   return UniqueDecls.size();
 }
 
+QualType
+OMPClauseMappableExprCommon::getComponentExprElementType(const Expr *Exp) {
+  assert(!isa<OMPArrayShapingExpr>(Exp) &&
+         "Cannot get element-type from array-shaping expr.");
+
+  // Unless we are handling array-section expressions, including
+  // array-subscripts, derefs, we can rely on getType.
+  if (!isa<ArraySectionExpr>(Exp))
+    return Exp->getType().getNonReferenceType().getCanonicalType();
+
+  // For array-sections, we need to find the type of one element of
+  // the section.
+  const auto *OASE = cast<ArraySectionExpr>(Exp);
+
+  QualType BaseType = ArraySectionExpr::getBaseOriginalType(OASE->getBase());
+
+  QualType ElemTy;
+  if (const auto *ATy = BaseType->getAsArrayTypeUnsafe())
+    ElemTy = ATy->getElementType();
+  else
+    ElemTy = BaseType->getPointeeType();
+
+  ElemTy = ElemTy.getNonReferenceType().getCanonicalType();
+  return ElemTy;
+}
+
+std::pair<const Expr *, std::optional<size_t>>
+OMPClauseMappableExprCommon::findAttachPtrExpr(
+    MappableExprComponentListRef Components, OpenMPDirectiveKind CurDirKind) {
+
+  // If we only have a single component, we have a map like "map(p)", which
+  // cannot have a base-pointer.
+  if (Components.size() < 2)
+    return {nullptr, std::nullopt};
+
+  // Only check for non-contiguous sections on target_update, since we can
+  // assume array-sections are contiguous on maps on other constructs, even if
+  // we are not sure of it at compile-time, like for a[1:x][2].
+  if (Components.back().isNonContiguous() && CurDirKind == OMPD_target_update)
+    return {nullptr, std::nullopt};
+
+  // To find the attach base-pointer, we start with the second component,
+  // stripping away one component at a time, until we reach a pointer Expr
+  // (that is not a binary operator). The first such pointer should be the
+  // attach base-pointer for the component list.
+  for (size_t I = 1; I < Components.size(); ++I) {
+    const Expr *CurExpr = Components[I].getAssociatedExpression();
+    if (!CurExpr)
+      break;
+
+    // If CurExpr is something like `p + 10`, we need to ignore it, since
+    // we are looking for `p`.
+    if (isa<BinaryOperator>(CurExpr))
+      continue;
+
+    // Keep going until we reach an Expr of pointer type.
+    QualType CurType = getComponentExprElementType(CurExpr);
+    if (!CurType->isPointerType())
+      continue;
+
+    // We have found a pointer Expr. This must be the attach pointer.
+    return {CurExpr, Components.size() - I};
+  }
+
+  return {nullptr, std::nullopt};
+}
+
 OMPMapClause *OMPMapClause::Create(
     const ASTContext &C, const OMPVarListLocTy &Locs, ArrayRef<Expr *> Vars,
     ArrayRef<ValueDecl *> Declarations,

clang/lib/Basic/OpenMPKinds.cpp

@@ -650,6 +650,11 @@ bool clang::isOpenMPTargetDataManagementDirective(OpenMPDirectiveKind DKind) {
          DKind == OMPD_target_exit_data || DKind == OMPD_target_update;
 }
 
+bool clang::isOpenMPTargetMapEnteringDirective(OpenMPDirectiveKind DKind) {
+  return DKind == OMPD_target_data || DKind == OMPD_target_enter_data ||
+         isOpenMPTargetExecutionDirective(DKind);
+}
+
 bool clang::isOpenMPNestingTeamsDirective(OpenMPDirectiveKind DKind) {
   if (DKind == OMPD_teams)
     return true;