[llvm][OpenMP] Handle complex types in atomic read (#111377)

This patch adds functionality for atomically reading `llvm.struct`
types.

Fixes: #93441

Author: NimishMishra

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -7836,7 +7836,7 @@ OpenMPIRBuilder::createAtomicRead(const LocationDescription &Loc,
          "OMP Atomic expects a pointer to target memory");
   Type *XElemTy = X.ElemTy;
   assert((XElemTy->isFloatingPointTy() || XElemTy->isIntegerTy() ||
-          XElemTy->isPointerTy()) &&
+          XElemTy->isPointerTy() || XElemTy->isStructTy()) &&
          "OMP atomic read expected a scalar type");
 
   Value *XRead = nullptr;
@@ -7846,6 +7846,20 @@ OpenMPIRBuilder::createAtomicRead(const LocationDescription &Loc,
         Builder.CreateLoad(XElemTy, X.Var, X.IsVolatile, "omp.atomic.read");
     XLD->setAtomic(AO);
     XRead = cast<Value>(XLD);
+  } else if (XElemTy->isStructTy()) {
+    // FIXME: Add checks to ensure __atomic_load is emitted iff the
+    // target does not support `atomicrmw` of the size of the struct
+    LoadInst *OldVal = Builder.CreateLoad(XElemTy, X.Var, "omp.atomic.read");
+    OldVal->setAtomic(AO);
+    const DataLayout &LoadDL = OldVal->getModule()->getDataLayout();
+    unsigned LoadSize =
+        LoadDL.getTypeStoreSize(OldVal->getPointerOperand()->getType());
+    OpenMPIRBuilder::AtomicInfo atomicInfo(
+        &Builder, XElemTy, LoadSize * 8, LoadSize * 8, OldVal->getAlign(),
+        OldVal->getAlign(), true /* UseLibcall */, X.Var);
+    auto AtomicLoadRes = atomicInfo.EmitAtomicLoadLibcall(AO);
+    XRead = AtomicLoadRes.first;
+    OldVal->eraseFromParent();
   } else {
     // We need to perform atomic op as integer
     IntegerType *IntCastTy =

mlir/test/Target/LLVMIR/openmp-llvm.mlir

@@ -1525,6 +1525,28 @@ llvm.func @_QPomp_atomic_capture_complex() {
 
 // -----
 
+// CHECK-LABEL: define void @omp_atomic_read_complex() {
+llvm.func @omp_atomic_read_complex(){
+
+// CHECK: %[[a:.*]] = alloca { float, float }, i64 1, align 8
+// CHECK: %[[b:.*]] = alloca { float, float }, i64 1, align 8
+// CHECK: %[[ATOMIC_TEMP_LOAD:.*]] = alloca { float, float }, align 8
+// CHECK: call void @__atomic_load(i64 8, ptr %[[b]], ptr %[[ATOMIC_TEMP_LOAD]], i32 0)
+// CHECK: %[[LOADED_VAL:.*]] = load { float, float }, ptr %[[ATOMIC_TEMP_LOAD]], align 8
+// CHECK: store { float, float } %[[LOADED_VAL]], ptr %[[a]], align 4
+// CHECK: ret void
+// CHECK: }
+
+    %0 = llvm.mlir.constant(1 : i64) : i64
+    %1 = llvm.alloca %0 x !llvm.struct<(f32, f32)> {bindc_name = "ib"} : (i64) -> !llvm.ptr
+    %2 = llvm.mlir.constant(1 : i64) : i64
+    %3 = llvm.alloca %2 x !llvm.struct<(f32, f32)> {bindc_name = "ia"} : (i64) -> !llvm.ptr
+    omp.atomic.read %1 = %3 : !llvm.ptr, !llvm.struct<(f32, f32)>
+    llvm.return
+}
+
+// -----
+
 // Checking an order-dependent operation when the order is `expr binop x`
 // CHECK-LABEL: @omp_atomic_update_ordering
 // CHECK-SAME: (ptr %[[x:.*]], i32 %[[expr:.*]])