[llvm] [mlir] [mlir][OpenMP] - Implement lowering from MLIR to LLVMIR for `private` clause on `target` constructs (PR #105471)

[Kareem Ergawy via llvm-commits]

================
@@ -0,0 +1,73 @@
+// RUN: mlir-translate -mlir-to-llvmir %s | FileCheck %s
+
+omp.private {type = private} @simple_var.privatizer : !llvm.ptr alloc {
+^bb0(%arg0: !llvm.ptr):
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x i32 {bindc_name = "simple_var", pinned} : (i64) -> !llvm.ptr
+  omp.yield(%1 : !llvm.ptr)
+}
+llvm.func @target_map_single_private() attributes {fir.internal_name = "_QPtarget_map_single_private"} {
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x i32 {bindc_name = "simple_var"} : (i64) -> !llvm.ptr
+  %2 = llvm.mlir.constant(1 : i64) : i64
+  %3 = llvm.alloca %2 x i32 {bindc_name = "a"} : (i64) -> !llvm.ptr
+  %4 = llvm.mlir.constant(2 : i32) : i32
+  llvm.store %4, %3 : i32, !llvm.ptr
+  %5 = omp.map.info var_ptr(%3 : !llvm.ptr, i32) map_clauses(to) capture(ByRef) -> !llvm.ptr {name = "a"}
+  omp.target map_entries(%5 -> %arg0 : !llvm.ptr) private(@simple_var.privatizer %1 -> %arg1 : !llvm.ptr) {
+  ^bb0(%arg0: !llvm.ptr, %arg1: !llvm.ptr):
+    %6 = llvm.mlir.constant(10 : i32) : i32
+    %7 = llvm.load %arg0 : !llvm.ptr -> i32
+    %8 = llvm.add %7, %6 : i32
+    llvm.store %8, %arg1 : i32, !llvm.ptr
+    omp.terminator
+  }
+  llvm.return
+}
+// CHECK: define internal void @__omp_offloading_fd00
+// CHECK-DAG: %[[PRIV_ALLOC:.*]] = alloca i32, i64 1, align 4
+// CHECK-DAG: %[[ADD:.*]] = add i32 {{.*}}, 10
+// CHECK-DAG: store i32 %[[ADD]], ptr %[[PRIV_ALLOC]], align 4
+
+omp.private {type = private} @n.privatizer : !llvm.ptr alloc {
+^bb0(%arg0: !llvm.ptr):
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x f32 {bindc_name = "n", pinned} : (i64) -> !llvm.ptr
+  omp.yield(%1 : !llvm.ptr)
+}
+llvm.func @target_map_2_privates() attributes {fir.internal_name = "_QPtarget_map_2_privates"} {
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x i32 {bindc_name = "simple_var"} : (i64) -> !llvm.ptr
+  %2 = llvm.mlir.constant(1 : i64) : i64
+  %3 = llvm.alloca %2 x f32 {bindc_name = "n"} : (i64) -> !llvm.ptr
+  %4 = llvm.mlir.constant(1 : i64) : i64
+  %5 = llvm.alloca %4 x i32 {bindc_name = "a"} : (i64) -> !llvm.ptr
----------------
ergawy wrote:

Just to reduce the test code a bit.
```suggestion
  %0 = llvm.mlir.constant(1 : i64) : i64
  %1 = llvm.alloca %0 x i32 {bindc_name = "simple_var"} : (i64) -> !llvm.ptr
  %3 = llvm.alloca %0 x f32 {bindc_name = "n"} : (i64) -> !llvm.ptr
  %5 = llvm.alloca %0 x i32 {bindc_name = "a"} : (i64) -> !llvm.ptr
```

https://github.com/llvm/llvm-project/pull/105471