[clang] [NFC][Clang][OpenMP] Add helper functions/utils for finding/comparing attach base-ptrs. (PR #155625)

[Abhinav Gaba via cfe-commits]

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@@ -6765,12 +6765,255 @@ llvm::Value *CGOpenMPRuntime::emitNumThreadsForTargetDirective(
 namespace {
 LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
 
+/// Utility to compare expression locations.
+/// Returns true if expr-loc of LHS is less-than that of RHS.
+/// This function asserts that both expressions have valid expr-locations.
+static bool compareExprLocs(const Expr *LHS, const Expr *RHS) {
+  // Assert that neither LHS nor RHS can be null
+  assert(LHS && "LHS expression cannot be null");
+  assert(RHS && "RHS expression cannot be null");
+
+  // Get source locations
+  SourceLocation LocLHS = LHS->getExprLoc();
+  SourceLocation LocRHS = RHS->getExprLoc();
+
+  // Assert that we have valid source locations
+  assert(LocLHS.isValid() && "LHS expression must have valid source location");
+  assert(LocRHS.isValid() && "RHS expression must have valid source location");
+
+  // Compare source locations for deterministic ordering
+  return LocLHS < LocRHS;
+}
+
 // Utility to handle information from clauses associated with a given
 // construct that use mappable expressions (e.g. 'map' clause, 'to' clause).
 // It provides a convenient interface to obtain the information and generate
 // code for that information.
 class MappableExprsHandler {
 public:
+  /// Custom comparator for attach-pointer expressions that compares them by
+  /// complexity (i.e. their component-depth) first, then by their expr-locs if
+  /// they are semantically different.
----------------
abhinavgaba wrote:

Do you mean always returning `true`? That would introduce a logical inconsistency, if the comparison is made from two different places in different order:

```c
a < b == true
b < a == true 
```

The `exprLoc` comparison will deterministically return the same result based on which clause was specified first by the user. 


https://github.com/llvm/llvm-project/pull/155625