[MLIR][OpenMP] - Fix translation of omp.target when private variables need cleaning up (#129205)

This is a simple fix that ensures that the InsertPoint is properly fixed
up after we have translated the dealloc region of all privatized
variables during translation of omp.target from MLIR to LLVMIR.

Fix for #129202

Author: bhandarkar-pranav

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

@@ -4832,6 +4832,7 @@ convertOmpTarget(Operation &opInst, llvm::IRBuilderBase &builder,
             "failed to inline `dealloc` region of `omp.private` "
             "op in the target region");
       }
+      return builder.saveIP();
     }
 
     return InsertPointTy(exitBlock.get(), exitBlock.get()->end());

mlir/test/Target/LLVMIR/openmp-target-private-allocatable.mlir

@@ -8,7 +8,15 @@ omp.private {type = private} @box.heap_privatizer : !llvm.struct<(ptr, i64, i32,
   llvm.call @alloc_foo_1(%arg0) : (!llvm.ptr) -> ()
   omp.yield(%arg1 : !llvm.ptr)
 } dealloc {
+// There is no reason for the dealloc region here to have two blocks.
+// But a multi-block test is useful in checking that the OMPIRBuilder
+// has updated the InsertPoint properly after translating the dealloc
+// region to LLVMIR.
+// See https://github.com/llvm/llvm-project/issues/129202 for more
+// context
 ^bb0(%arg0: !llvm.ptr):
+  llvm.br ^bb1
+^bb1:
   llvm.call @dealloc_foo_1(%arg0) : (!llvm.ptr) -> ()
   omp.yield
 }
@@ -60,3 +68,6 @@ llvm.func @_FortranAAssign(!llvm.ptr, !llvm.ptr, !llvm.ptr, i32) -> !llvm.struct
 
 // Now, check the deallocation of the private var.
 // CHECK:  call void @dealloc_foo_1(ptr %[[DESC_TO_DEALLOC]])
+// CHECK-NEXT: br label %[[CONT_BLOCK:.*]]
+// CHECK: [[CONT_BLOCK]]:
+// CHECK-NEXT: ret void