From 392cba8603efc41991613d3b3faaca21fd322500 Mon Sep 17 00:00:00 2001
From: Jean Perier <jperier@nvidia.com>
Date: Thu, 3 Mar 2022 10:11:19 +0100
Subject: [PATCH] [flang] Handle optional TARGET associate in ASSOCIATED
 runtime

The TARGET argument of ASSOCIATED may be dynamically optional, in which
case ASSOCIATED(POINTER, TARGET) is equal to ASSOCIATED(TARGET).

Make the runtime argument a pointer so that it can detect and handle
arguments that are dynamically optional.

Also fix the runtime to check if TARGET base address is not null and if
its element size is not null to match the requirement of ASSOCIATED
regarding TARGET:
- if TARGET is an object: true iff [..] TARGET is not a zerosized storage sequence
- if TARGET is a POINTER: true iff [..] POINTER and TARGET are associated

Not that ASSOCIATED will also returns false if TARGET is an unallocated allocatable.
This is not described in the standard, but is a unanimous behaviour of
existing compilers.

Differential Revision: https://reviews.llvm.org/D120835
---
 flang/include/flang/Runtime/pointer.h |  2 +-
 flang/runtime/pointer.cpp             | 16 +++++++++++-----
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/flang/include/flang/Runtime/pointer.h b/flang/include/flang/Runtime/pointer.h
index ea3e5b7558da..5bb86dbf4954 100644
--- a/flang/include/flang/Runtime/pointer.h
+++ b/flang/include/flang/Runtime/pointer.h
@@ -105,7 +105,7 @@ bool RTNAME(PointerIsAssociated)(const Descriptor &);
 
 // True when the pointer is associated with a specific target.
 bool RTNAME(PointerIsAssociatedWith)(
-    const Descriptor &, const Descriptor &target);
+    const Descriptor &, const Descriptor *target);
 
 } // extern "C"
 } // namespace Fortran::runtime
diff --git a/flang/runtime/pointer.cpp b/flang/runtime/pointer.cpp
index dd41e1f060aa..8aebf1a60304 100644
--- a/flang/runtime/pointer.cpp
+++ b/flang/runtime/pointer.cpp
@@ -147,16 +147,22 @@ bool RTNAME(PointerIsAssociated)(const Descriptor &pointer) {
 }
 
 bool RTNAME(PointerIsAssociatedWith)(
-    const Descriptor &pointer, const Descriptor &target) {
+    const Descriptor &pointer, const Descriptor *target) {
+  if (!target) {
+    return pointer.raw().base_addr != nullptr;
+  }
+  if (!target->raw().base_addr || target->ElementBytes() == 0) {
+    return false;
+  }
   int rank{pointer.rank()};
-  if (pointer.raw().base_addr != target.raw().base_addr ||
-      pointer.ElementBytes() != target.ElementBytes() ||
-      rank != target.rank()) {
+  if (pointer.raw().base_addr != target->raw().base_addr ||
+      pointer.ElementBytes() != target->ElementBytes() ||
+      rank != target->rank()) {
     return false;
   }
   for (int j{0}; j < rank; ++j) {
     const Dimension &pDim{pointer.GetDimension(j)};
-    const Dimension &tDim{target.GetDimension(j)};
+    const Dimension &tDim{target->GetDimension(j)};
     if (pDim.Extent() != tDim.Extent() ||
         pDim.ByteStride() != tDim.ByteStride()) {
       return false;