[Flang][MLIR][OpenMP] Fix Target Data if (present(...)) causing LLVM-… (llvm#2526)

Author: ronlieb

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

@@ -4158,6 +4158,9 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
       }
       break;
     case BodyGenTy::DupNoPriv:
+      // We must always restoreIP regardless of doing anything the caller
+      // does not restore it, leading to incorrect (no) branch generation.
+      builder.restoreIP(codeGenIP);
       break;
     case BodyGenTy::NoPriv:
       // If device info is available then region has already been generated

offload/test/offloading/fortran/target-data-map-if-present.f90

@@ -0,0 +1,29 @@
+! Offloading test that tests that if(present(a)) compiles and executes without
+! causing any compilation errors, primarily a regression test that does not
+! yield interesting results.
+! REQUIRES: flang, amdgpu
+
+! RUN: %libomptarget-compile-fortran-run-and-check-generic
+module mod
+    implicit none
+contains
+    subroutine routine(a)
+        implicit none
+        real, dimension(:), optional :: a
+        integer :: i
+       !$omp target data if(present(a)) map(alloc:a)
+            do i = 1, 10
+                a(i) = i
+            end do
+       !$omp end target data
+    end subroutine routine
+end module mod
+
+program main
+    use mod
+    real :: a(10)
+    call routine(a)
+    print *, a
+end program main
+
+! CHECK: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.