[llvm-branch-commits] [mlir] [mlir][OpenMP] Pack task private variables into a heap-allocated context struct (PR #125307)

[Tom Eccles via llvm-branch-commits]

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@@ -1730,6 +1730,126 @@ buildDependData(std::optional<ArrayAttr> dependKinds, OperandRange dependVars,
   }
 }
 
+static bool privatizerReadsSourceVariable(omp::PrivateClauseOp &priv) {
+  if (priv.getDataSharingType() == omp::DataSharingClauseType::FirstPrivate)
+    return true;
+
+  Region &initRegion = priv.getInitRegion();
+  if (initRegion.empty())
+    return false;
+
+  BlockArgument sourceVariable = priv.getInitMoldArg();
+  if (!sourceVariable)
+    return false;
+  return !sourceVariable.use_empty();
+}
+
+namespace {
+/// TaskContextStructManager takes care of creating and freeing a structure
+/// containing information needed by the task body to execute.
+class TaskContextStructManager {
+public:
+  TaskContextStructManager(llvm::IRBuilderBase &builder,
+                           LLVM::ModuleTranslation &moduleTranslation,
+                           MutableArrayRef<omp::PrivateClauseOp> privateDecls)
+      : builder{builder}, moduleTranslation{moduleTranslation},
+        privateDecls{privateDecls} {}
+
+  /// Creates a heap allocated struct containing space for each private
+  /// variable. Returns nullptr if there are is no struct needed. Invariant:
+  /// privateVarTypes, privateDecls, and the elements of the structure should
+  /// all have the same order (although privateDecls which do not read from the
+  /// mold argument are skipped).
+  void generateTaskContextStruct();
+
+  /// Create GEPs to access each member of the structure representing a private
+  /// variable, adding them to llvmPrivateVars. Null values are added where
+  /// private decls were skipped so that the ordering continues to match the
+  /// private decls.
+  void createGEPsToPrivateVars(SmallVectorImpl<llvm::Value *> &llvmPrivateVars);
+
+  /// De-allocate the task context structure.
+  void freeStructPtr();
+
+  llvm::Value *getStructPtr() { return structPtr; }
+
+private:
+  llvm::IRBuilderBase &builder;
+  LLVM::ModuleTranslation &moduleTranslation;
+  MutableArrayRef<omp::PrivateClauseOp> privateDecls;
----------------
tblah wrote:

I agree it should be, but unfortunately the table-gen accessors (e.g. `getRegions()`, `getCopyRegion()`) for the mlir operation aren't marked `const`. This makes sense because the region can be mutated through this reference, but it is a shame there aren't any `const` alternatives.

The non-const regions means that `getInitMoldArg()` etc cannot be `const`.

https://github.com/llvm/llvm-project/pull/125307