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

[Kareem Ergawy via llvm-branch-commits]

================
@@ -1796,36 +1918,110 @@ convertOmpTaskOp(omp::TaskOp taskOp, llvm::IRBuilderBase &builder,
   // Allocate and initialize private variables
   // TODO: package private variables up in a structure
   builder.SetInsertPoint(initBlock->getTerminator());
-  for (auto [privDecl, mlirPrivVar, blockArg] :
-       llvm::zip_equal(privateDecls, mlirPrivateVars, privateBlockArgs)) {
-    llvm::Type *llvmAllocType =
-        moduleTranslation.convertType(privDecl.getType());
 
-    // Allocations:
-    builder.SetInsertPoint(allocaIP.getBlock()->getTerminator());
-    llvm::Value *llvmPrivateVar = builder.CreateAlloca(
-        llvmAllocType, /*ArraySize=*/nullptr, "omp.private.alloc");
+  // Create task variable structure
+  llvm::SmallVector<llvm::Value *> privateVarAllocations;
+  taskStructMgr.generateTaskContextStruct();
+  // GEPs so that we can initialize the variables. Don't use these GEPs inside
+  // of the body otherwise it will be the GEP not the struct which is fowarded
+  // to the outlined function. GEPs forwarded in this way are passed in a
+  // stack-allocated (by OpenMPIRBuilder) structure which is not safe for tasks
+  // which may not be executed until after the current stack frame goes out of
+  // scope.
+  taskStructMgr.createGEPsToPrivateVars(privateVarAllocations);
+
+  for (auto [privDecl, mlirPrivVar, blockArg, llvmPrivateVarAlloc] :
+       llvm::zip_equal(privateDecls, mlirPrivateVars, privateBlockArgs,
+                       privateVarAllocations)) {
+    if (!llvmPrivateVarAlloc)
----------------
ergawy wrote:

nit: Just to more easily constrast it with the other loop below.
```suggestion
    if (!privatizerReadsSourceVariable(privDecl))
```

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