[clang] [llvm] [mlir] [OMPIRBuilder] - Handle dependencies in `createTarget` (PR #93977)

[Michael Kruse via cfe-commits]

================
@@ -1698,6 +1701,64 @@ void OpenMPIRBuilder::createTaskyield(const LocationDescription &Loc) {
   emitTaskyieldImpl(Loc);
 }
 
+// Processes the dependencies in Dependencies and does the following
+// - Allocates space on the stack of an array of DependInfo objects
+// - Populates each DependInfo object with relevant information of
+//   the corresponding dependence.
+// - All code is inserted in the entry block of the current function.
+static Value *
+emitDepArray(OpenMPIRBuilder &OMPBuilder,
+             SmallVector<OpenMPIRBuilder::DependData> &Dependencies) {
+  // Early return if we have no dependencies to process
+  if (!Dependencies.size())
+    return nullptr;
+
+  IRBuilderBase &Builder = OMPBuilder.Builder;
+  Type *DependInfo = OMPBuilder.DependInfo;
+  Module &M = OMPBuilder.M;
+
+  Value *DepArray = nullptr;
+  if (Dependencies.size()) {
+    OpenMPIRBuilder::InsertPointTy OldIP = Builder.saveIP();
+    Builder.SetInsertPoint(
+        &OldIP.getBlock()->getParent()->getEntryBlock().back());
+
+    Type *DepArrayTy = ArrayType::get(DependInfo, Dependencies.size());
+    DepArray = Builder.CreateAlloca(DepArrayTy, nullptr, ".dep.arr.addr");
+
+    unsigned P = 0;
+    for (const OpenMPIRBuilder::DependData &Dep : Dependencies) {
+      Value *Base =
+          Builder.CreateConstInBoundsGEP2_64(DepArrayTy, DepArray, 0, P);
+      // Store the pointer to the variable
+      Value *Addr = Builder.CreateStructGEP(
+          DependInfo, Base,
+          static_cast<unsigned int>(RTLDependInfoFields::BaseAddr));
+      Value *DepValPtr =
+          Builder.CreatePtrToInt(Dep.DepVal, Builder.getInt64Ty());
+      Builder.CreateStore(DepValPtr, Addr);
+      // Store the size of the variable
+      Value *Size = Builder.CreateStructGEP(
+          DependInfo, Base,
+          static_cast<unsigned int>(RTLDependInfoFields::Len));
+      Builder.CreateStore(Builder.getInt64(M.getDataLayout().getTypeStoreSize(
+                              Dep.DepValueType)),
+                          Size);
+      // Store the dependency kind
+      Value *Flags = Builder.CreateStructGEP(
+          DependInfo, Base,
+          static_cast<unsigned int>(RTLDependInfoFields::Flags));
+      Builder.CreateStore(
+          ConstantInt::get(Builder.getInt8Ty(),
+                           static_cast<unsigned int>(Dep.DepKind)),
+          Flags);
----------------
Meinersbur wrote:

Consider adding a comment with a mock source of what is generate here:
```
DepArray[P].BaseAddre = ...
```

https://github.com/llvm/llvm-project/pull/93977