diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 91aa15d..ba071e8 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -10579,6 +10579,7 @@ gimplify_adjust_omp_clauses_1 (splay_tree_node n, void *data)
 	  gcc_unreachable ();
 	}
       OMP_CLAUSE_SET_MAP_KIND (clause, kind);
+      OMP_CLAUSE_MAP_IMPLICIT_P (clause) = 1;
       if (DECL_SIZE (decl)
 	  && TREE_CODE (DECL_SIZE (decl)) != INTEGER_CST)
 	{
@@ -11158,9 +11159,15 @@ gimplify_adjust_omp_clauses (gimple_seq *pre_p, gimple_seq body, tree *list_p,
 	list_p = &OMP_CLAUSE_CHAIN (c);
     }
 
-  /* Add in any implicit data sharing.  */
+  /* Add in any implicit data sharing. Implicit clauses are added at the start
+     of the clause list, but after any non-map clauses.  */
   struct gimplify_adjust_omp_clauses_data data;
-  data.list_p = list_p;
+  tree *implicit_add_list_p = orig_list_p;
+  while (*implicit_add_list_p
+	 && OMP_CLAUSE_CODE (*implicit_add_list_p) != OMP_CLAUSE_MAP)
+    implicit_add_list_p = &OMP_CLAUSE_CHAIN (*implicit_add_list_p);
+
+  data.list_p = implicit_add_list_p;
   data.pre_p = pre_p;
   splay_tree_foreach (ctx->variables, gimplify_adjust_omp_clauses_1, &data);
 
diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index 66519ad..64b7c19 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -12920,6 +12920,19 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 		    else if (integer_nonzerop (s))
 		      tkind_zero = tkind;
 		  }
+		if (tkind_zero == tkind
+		    && OMP_CLAUSE_MAP_IMPLICIT_P (c)
+		    && (((tkind & GOMP_MAP_FLAG_SPECIAL_BITS)
+			 & ~GOMP_MAP_IMPLICIT)
+			== 0))
+		  {
+		    /* If this is an implicit map, and the GOMP_MAP_IMPLICIT
+		       bits are not interfered by other special bit encodings,
+		       then turn the GOMP_IMPLICIT_BIT flag on for the runtime
+		       to see.  */
+		    tkind |= GOMP_MAP_IMPLICIT;
+		    tkind_zero = tkind;
+		  }
 		break;
 	      case OMP_CLAUSE_FIRSTPRIVATE:
 		gcc_checking_assert (is_gimple_omp_oacc (ctx->stmt));
diff --git a/gcc/testsuite/c-c++-common/goacc/combined-reduction.c b/gcc/testsuite/c-c++-common/goacc/combined-reduction.c
index ecf23f5..fa67e08 100644
--- a/gcc/testsuite/c-c++-common/goacc/combined-reduction.c
+++ b/gcc/testsuite/c-c++-common/goacc/combined-reduction.c
@@ -23,7 +23,7 @@ main ()
   return 0;
 }
 
-/* { dg-final { scan-tree-dump-times "omp target oacc_parallel reduction.+:v1. map.tofrom:v1" 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "omp target oacc_parallel reduction.+:v1. firstprivate.n. map.tofrom:v1" 1 "gimple" } } */
 /* { dg-final { scan-tree-dump-times "acc loop reduction.+:v1. private.i." 1 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "omp target oacc_kernels map.force_tofrom:n .len: 4.. map.force_tofrom:v1 .len: 4.." 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "omp target oacc_kernels map.force_tofrom:n .len: 4..implicit.. map.force_tofrom:v1 .len: 4..implicit.." 1 "gimple" } } */
 /* { dg-final { scan-tree-dump-times "acc loop reduction.+:v1. private.i." 1 "gimple" } } */
diff --git a/gcc/testsuite/c-c++-common/goacc/firstprivate-mappings-1.c b/gcc/testsuite/c-c++-common/goacc/firstprivate-mappings-1.c
index 7987bea..f43e4b4 100644
--- a/gcc/testsuite/c-c++-common/goacc/firstprivate-mappings-1.c
+++ b/gcc/testsuite/c-c++-common/goacc/firstprivate-mappings-1.c
@@ -419,12 +419,12 @@ vla (int array_li)
   copyout (array_so)
   /* The gimplifier has created an implicit 'firstprivate' clause for the array
      length.
-     { dg-final { scan-tree-dump {(?n)#pragma omp target oacc_parallel map\(from:array_so \[len: 4\]\) firstprivate\(array_li.[0-9]+\)} omplower { target { ! c++ } } } }
-     { dg-final { scan-tree-dump {(?n)#pragma omp target oacc_parallel map\(from:array_so \[len: 4\]\) firstprivate\(} omplower { target { c++ } } } }
+     { dg-final { scan-tree-dump {(?n)#pragma omp target oacc_parallel firstprivate\(array_li.[0-9]+\) map\(from:array_so \[len: 4\]\)} omplower { target { ! c++ } } } }
+     { dg-final { scan-tree-dump {(?n)#pragma omp target oacc_parallel firstprivate\([^)]+\) map\(from:array_so \[len: 4\]\)} omplower { target { c++ } } } }
      (C++ computes an intermediate value, so can't scan for 'firstprivate(array_li)'.)  */
   /* For C, non-LP64, the gimplifier has also created a mapping for the array
      itself; PR90859.
-     { dg-final { scan-tree-dump {(?n)#pragma omp target oacc_parallel map\(from:array_so \[len: 4\]\) firstprivate\(array_li.[0-9]+\) map\(tofrom:\(\*array.[0-9]+\) \[len: D\.[0-9]+\]\) map\(firstprivate:array \[pointer assign, bias: 0\]\) \[} omplower { target { c && { ! lp64 } } } } } */
+     { dg-final { scan-tree-dump {(?n)#pragma omp target oacc_parallel firstprivate\(array_li.[0-9]+\) map\(tofrom:\(\*array.[0-9]+\) \[len: D\.[0-9]+\]\[implicit\]\) map\(firstprivate:array \[pointer assign, bias: 0\]\) map\(from:array_so \[len: 4\]\) \[} omplower { target { c && { ! lp64 } } } } } */
   {
     array_so = sizeof array;
   }
diff --git a/gcc/testsuite/c-c++-common/goacc/mdc-1.c b/gcc/testsuite/c-c++-common/goacc/mdc-1.c
index 337c1f7..9f43de4 100644
--- a/gcc/testsuite/c-c++-common/goacc/mdc-1.c
+++ b/gcc/testsuite/c-c++-common/goacc/mdc-1.c
@@ -45,7 +45,7 @@ t1 ()
 
 /* { dg-final { scan-tree-dump-times "pragma omp target oacc_enter_exit_data map.to:s .len: 32.." 1 "omplower" } } */
 /* { dg-final { scan-tree-dump-times "pragma omp target oacc_data map.tofrom:.z .len: 40.. map.struct:s .len: 1.. map.alloc:s.a .len: 8.. map.tofrom:._1 .len: 40.. map.attach:s.a .bias: 0.." 1 "omplower" } } */
-/* { dg-final { scan-tree-dump-times "pragma omp target oacc_parallel map.attach:s.e .bias: 0.. map.tofrom:s .len: 32" 1 "omplower" } } */
+/* { dg-final { scan-tree-dump-times "pragma omp target oacc_parallel map.tofrom:s .len: 32..implicit.. map.attach:s.e .bias: 0.." 1 "omplower" } } */
 /* { dg-final { scan-tree-dump-times "pragma omp target oacc_enter_exit_data map.attach:a .bias: 0.." 1 "omplower" } } */
 /* { dg-final { scan-tree-dump-times "pragma omp target oacc_enter_exit_data map.detach:a .bias: 0.." 1 "omplower" } } */
 /* { dg-final { scan-tree-dump-times "pragma omp target oacc_enter_exit_data map.to:a .len: 8.." 1 "omplower" } } */
diff --git a/gcc/testsuite/c-c++-common/goacc/reduction-1.c b/gcc/testsuite/c-c++-common/goacc/reduction-1.c
index 35bfc86..d9e3c38 100644
--- a/gcc/testsuite/c-c++-common/goacc/reduction-1.c
+++ b/gcc/testsuite/c-c++-common/goacc/reduction-1.c
@@ -68,5 +68,5 @@ main(void)
 }
 
 /* Check that default copy maps are generated for loop reductions.  */
-/* { dg-final { scan-tree-dump-times "map\\(tofrom:result \\\[len: \[0-9\]+\\\]\\)" 7 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "map\\(tofrom:lresult \\\[len: \[0-9\]+\\\]\\)" 2 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map\\(tofrom:result \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 7 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map\\(tofrom:lresult \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 2 "gimple" } } */
diff --git a/gcc/testsuite/c-c++-common/goacc/reduction-2.c b/gcc/testsuite/c-c++-common/goacc/reduction-2.c
index 9dba035..18dc03c 100644
--- a/gcc/testsuite/c-c++-common/goacc/reduction-2.c
+++ b/gcc/testsuite/c-c++-common/goacc/reduction-2.c
@@ -50,5 +50,5 @@ main(void)
 }
 
 /* Check that default copy maps are generated for loop reductions.  */
-/* { dg-final { scan-tree-dump-times "map\\(tofrom:result \\\[len: \[0-9\]+\\\]\\)" 4 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "map\\(tofrom:lresult \\\[len: \[0-9\]+\\\]\\)" 2 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map\\(tofrom:result \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 4 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map\\(tofrom:lresult \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 2 "gimple" } } */
diff --git a/gcc/testsuite/c-c++-common/goacc/reduction-3.c b/gcc/testsuite/c-c++-common/goacc/reduction-3.c
index 669cd43..2311d4b 100644
--- a/gcc/testsuite/c-c++-common/goacc/reduction-3.c
+++ b/gcc/testsuite/c-c++-common/goacc/reduction-3.c
@@ -50,5 +50,5 @@ main(void)
 }
 
 /* Check that default copy maps are generated for loop reductions.  */
-/* { dg-final { scan-tree-dump-times "map\\(tofrom:result \\\[len: \[0-9\]+\\\]\\)" 4 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "map\\(tofrom:lresult \\\[len: \[0-9\]+\\\]\\)" 2 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map\\(tofrom:result \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 4 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map\\(tofrom:lresult \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 2 "gimple" } } */
diff --git a/gcc/testsuite/c-c++-common/goacc/reduction-4.c b/gcc/testsuite/c-c++-common/goacc/reduction-4.c
index 5c3dfb1..57823f8 100644
--- a/gcc/testsuite/c-c++-common/goacc/reduction-4.c
+++ b/gcc/testsuite/c-c++-common/goacc/reduction-4.c
@@ -38,5 +38,5 @@ main(void)
 }
 
 /* Check that default copy maps are generated for loop reductions.  */
-/* { dg-final { scan-tree-dump-times "map\\(tofrom:result \\\[len: \[0-9\]+\\\]\\)" 2 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "map\\(tofrom:lresult \\\[len: \[0-9\]+\\\]\\)" 2 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map\\(tofrom:result \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 2 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map\\(tofrom:lresult \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 2 "gimple" } } */
diff --git a/gcc/testsuite/c-c++-common/goacc/reduction-8.c b/gcc/testsuite/c-c++-common/goacc/reduction-8.c
index 8a0283f..8494e59 100644
--- a/gcc/testsuite/c-c++-common/goacc/reduction-8.c
+++ b/gcc/testsuite/c-c++-common/goacc/reduction-8.c
@@ -87,8 +87,10 @@ main(void)
 
 /* Check that default copy maps are generated for loop reductions.  */
 /* { dg-final { scan-tree-dump-times "reduction..:result. map.tofrom:result .len: 4.." 1 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "oacc_parallel map.tofrom:result .len: 4.." 2 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "map.tofrom:array .len: 4000.. firstprivate.result." 3 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "map.tofrom:result .len: 4.. map.tofrom:array .len: 4000.." 1 "gimple" } } */
-/* { dg-final { scan-tree-dump-times "map.tofrom:array .len: 4000.. map.force_tofrom:result .len: 4.." 1 "gimple" } } */
+
+/* { dg-final { scan-tree-dump-times "oacc_parallel map.tofrom:result .len: 4..implicit.." 1 "gimple" } } */
+
+/* { dg-final { scan-tree-dump-times "map.tofrom:array .len: 4000..implicit.. firstprivate.result." 3 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map.tofrom:array .len: 4000..implicit.. map.tofrom:result .len: 4.." 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "map.tofrom:array .len: 4000..implicit.. map.force_tofrom:result .len: 4..implicit.." 1 "gimple" } } */
 
diff --git a/gcc/testsuite/c-c++-common/gomp/target-implicit-map-1.c b/gcc/testsuite/c-c++-common/gomp/target-implicit-map-1.c
new file mode 100644
index 0000000..52944fd
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/gomp/target-implicit-map-1.c
@@ -0,0 +1,39 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-fdump-tree-gimple" } */
+#ifdef __cplusplus
+extern "C"
+#else
+extern
+#endif
+void abort (void);
+
+int
+main (void)
+{
+  #define N 5
+  int array[N][N];
+
+  for (int i = 0; i < N; i++)
+    {
+      #pragma omp target enter data map(alloc: array[i:1][0:N])
+
+      #pragma omp target
+      for (int j = 0; j < N; j++)
+	array[i][j] = i * 10 + j;
+
+      #pragma omp target exit data map(from: array[i:1][0:N])
+    }
+
+  for (int i = 0; i < N; i++)
+    for (int j = 0; j < N; j++)
+      if (array[i][j] != i + j)
+	abort ();
+
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump {#pragma omp target enter data map\(alloc:array\[[^]]+\]\[0\] \[len: [0-9]+\]\)} "gimple" } } */
+
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(i\) map\(tofrom:array \[len: [0-9]+\]\[implicit\]\)} "gimple" } } */
+
+/* { dg-final { scan-tree-dump {#pragma omp target exit data map\(from:array\[[^]]+\]\[0\] \[len: [0-9]+\]\)} "gimple" } } */
diff --git a/gcc/testsuite/g++.dg/goacc/firstprivate-mappings-1.C b/gcc/testsuite/g++.dg/goacc/firstprivate-mappings-1.C
index 1b1badb..99a3bd4 100644
--- a/gcc/testsuite/g++.dg/goacc/firstprivate-mappings-1.C
+++ b/gcc/testsuite/g++.dg/goacc/firstprivate-mappings-1.C
@@ -416,7 +416,7 @@ vla (int &array_li)
   copyout (array_so)
   /* The gimplifier has created an implicit 'firstprivate' clause for the array
      length.
-     { dg-final { scan-tree-dump {(?n)#pragma omp target oacc_parallel map\(from:array_so \[len: 4\]\) firstprivate\(} omplower } }
+     { dg-final { scan-tree-dump {(?n)#pragma omp target oacc_parallel firstprivate\([^)]+\) map\(from:array_so \[len: 4\]\)} omplower } }
      (C++ computes an intermediate value, so can't scan for 'firstprivate(array_li)'.)  */
   {
     array_so = sizeof array;
diff --git a/gcc/testsuite/g++.dg/gomp/target-lambda-1.C b/gcc/testsuite/g++.dg/gomp/target-lambda-1.C
index 7dceef8..e5a24d7 100644
--- a/gcc/testsuite/g++.dg/gomp/target-lambda-1.C
+++ b/gcc/testsuite/g++.dg/gomp/target-lambda-1.C
@@ -87,8 +87,8 @@ int main (void)
   return 0;
 }
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(to:\*__closure \[len: [0-9]+\]\) map\(firstprivate:__closure \[pointer assign, bias: 0\]\) map\(attach_zero_length_array_section:__closure->__iptr \[bias: 0\]\) map\(struct:\*__closure \[len: 1\]\) map\(alloc:__closure->__this \[len: [0-9]+\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(always_pointer:__closure->__this \[pointer assign, bias: 0\]\) map\(attach_zero_length_array_section:_[0-9]+->ptr \[bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) firstprivate\(b\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:iptr \[pointer assign, bias: 0\]\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(b\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:iptr \[pointer assign, bias: 0\]\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(to:\*__closure \[len: [0-9]+\]\) map\(firstprivate:__closure \[pointer assign, bias: 0\]\) map\(attach_zero_length_array_section:__closure->__iptr \[bias: 0\]\) map\(struct:\*__closure \[len: 1\]\) map\(alloc:__closure->__this \[len: [0-9]+\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(always_pointer:__closure->__this \[pointer assign, bias: 0\]\) map\(attach_zero_length_array_section:_[0-9]+->ptr \[bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\)} "gimple" } } */
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(to:loop \[len: [0-9]+\]\) map\(attach_zero_length_array_section:loop\.__data1 \[bias: 0\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) firstprivate\(end\) firstprivate\(begin\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(end\) firstprivate\(begin\) map\(to:loop \[len: [0-9]+\]\) map\(attach_zero_length_array_section:loop\.__data1 \[bias: 0\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\)} "gimple" } } */
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(to:loop \[len: [0-9]+\]\) map\(attach_zero_length_array_section:loop\.__data2 \[bias: 0\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) firstprivate\(end\) firstprivate\(begin\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(end\) firstprivate\(begin\) map\(to:loop \[len: [0-9]+\]\) map\(attach_zero_length_array_section:loop\.__data2 \[bias: 0\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\)} "gimple" } } */
diff --git a/gcc/testsuite/g++.dg/gomp/target-this-3.C b/gcc/testsuite/g++.dg/gomp/target-this-3.C
index 08568f9..2755b4b 100644
--- a/gcc/testsuite/g++.dg/gomp/target-this-3.C
+++ b/gcc/testsuite/g++.dg/gomp/target-this-3.C
@@ -100,6 +100,6 @@ int main (void)
   return 0;
 }
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(tofrom:\*this \[len: [0-9]+\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(alloc:\*_[0-9]+ \[pointer assign, zero-length array section, bias: 0\]\) map\(attach:this->refptr \[bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9+] \[len: 0\]\) firstprivate\(n\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(n\) map\(tofrom:\*this \[len: [0-9]+\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(alloc:\*_[0-9]+ \[pointer assign, zero-length array section, bias: 0\]\) map\(attach:this->refptr \[bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9+] \[len: 0\]\)} "gimple" } } */
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(tofrom:\*this \[len: [0-9]+\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(attach_zero_length_array_section:this->ptr \[bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) firstprivate\(n\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(n\) map\(tofrom:\*this \[len: [0-9]+\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(attach_zero_length_array_section:this->ptr \[bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\)} "gimple" } } */
diff --git a/gcc/testsuite/g++.dg/gomp/target-this-4.C b/gcc/testsuite/g++.dg/gomp/target-this-4.C
index 3b2d581..3703762 100644
--- a/gcc/testsuite/g++.dg/gomp/target-this-4.C
+++ b/gcc/testsuite/g++.dg/gomp/target-this-4.C
@@ -102,6 +102,6 @@ int main (void)
   return 0;
 }
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(to:\*__closure \[len: [0-9]+\]\) map\(firstprivate:__closure \[pointer assign, bias: 0\]\) map\(struct:\*__closure \[len: 1\]\) map\(alloc:__closure->__this \[len: [0-9]+\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(always_pointer:__closure->__this \[pointer assign, bias: 0\]\) map\(attach_zero_length_array_section:_[0-9]+->ptr \[bias: 0\]\) map\(from:mapped \[len: 1\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) firstprivate\(n\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(n\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(to:\*__closure \[len: [0-9]+\]\) map\(firstprivate:__closure \[pointer assign, bias: 0\]\) map\(struct:\*__closure \[len: 1\]\) map\(alloc:__closure->__this \[len: [0-9]+\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(always_pointer:__closure->__this \[pointer assign, bias: 0\]\) map\(attach_zero_length_array_section:_[0-9]+->ptr \[bias: 0\]\) map\(from:mapped \[len: 1\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\)} "gimple" } } */
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(to:\*__closure \[len: [0-9]+\]\) map\(firstprivate:__closure \[pointer assign, bias: 0\]\) map\(struct:\*__closure \[len: 1\]\) map\(alloc:__closure->__this \[len: [0-9]+\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(always_pointer:__closure->__this \[pointer assign, bias: 0\]\) map\(alloc:\*_[0-9]+ \[pointer assign, zero-length array section, bias: 0\]\) map\(attach:_[0-9]+->refptr \[bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) firstprivate\(n\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(n\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(to:\*__closure \[len: [0-9]+\]\) map\(firstprivate:__closure \[pointer assign, bias: 0\]\) map\(struct:\*__closure \[len: 1\]\) map\(alloc:__closure->__this \[len: [0-9]+\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(always_pointer:__closure->__this \[pointer assign, bias: 0\]\) map\(alloc:\*_[0-9]+ \[pointer assign, zero-length array section, bias: 0\]\) map\(attach:_[0-9]+->refptr \[bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\)} "gimple" } } */
diff --git a/gcc/testsuite/gfortran.dg/goacc/common-block-3.f90 b/gcc/testsuite/gfortran.dg/goacc/common-block-3.f90
index e43d376..e9f169f 100644
--- a/gcc/testsuite/gfortran.dg/goacc/common-block-3.f90
+++ b/gcc/testsuite/gfortran.dg/goacc/common-block-3.f90
@@ -33,10 +33,10 @@ end program main
 
 ! { dg-final { scan-tree-dump-times "omp target oacc_data_kernels .*map\\(tofrom:x \\\[len: 400\\\]\\)" 1 "omplower" } }
 ! { dg-final { scan-tree-dump-times "omp target oacc_data_kernels .*map\\(tofrom:y \\\[len: 400\\\]\\\)" 1 "omplower" } }
-! { dg-final { scan-tree-dump-times "omp target oacc_kernels .*map\\(force_present:x \\\[len: 400\\\]\\)" 1 "omplower" } }
-! { dg-final { scan-tree-dump-times "omp target oacc_kernels .*map\\(force_present:y \\\[len: 400\\\]\\\)" 1 "omplower" } }
-! { dg-final { scan-tree-dump-times "omp target oacc_kernels .*map\\(force_tofrom:i \\\[len: 4\\\]\\)" 1 "omplower" } }
-! { dg-final { scan-tree-dump-times "omp target oacc_kernels .*map\\(force_tofrom:c \\\[len: 4\\\]\\)" 1 "omplower" } }
+! { dg-final { scan-tree-dump-times "omp target oacc_kernels .*map\\(force_present:x \\\[len: 400\\\]\\\[implicit\\\]\\)" 1 "omplower" } }
+! { dg-final { scan-tree-dump-times "omp target oacc_kernels .*map\\(force_present:y \\\[len: 400\\\]\\\[implicit\\\]\\\)" 1 "omplower" } }
+! { dg-final { scan-tree-dump-times "omp target oacc_kernels .*map\\(force_tofrom:i \\\[len: 4\\\]\\\[implicit\\\]\\)" 1 "omplower" } }
+! { dg-final { scan-tree-dump-times "omp target oacc_kernels .*map\\(force_tofrom:c \\\[len: 4\\\]\\\[implicit\\\]\\)" 1 "omplower" } }
 
 ! Expecting no mapping of un-referenced common-blocks variables
 
diff --git a/gcc/testsuite/gfortran.dg/goacc/loop-tree-1.f90 b/gcc/testsuite/gfortran.dg/goacc/loop-tree-1.f90
index 150f930..4cdfc55 100644
--- a/gcc/testsuite/gfortran.dg/goacc/loop-tree-1.f90
+++ b/gcc/testsuite/gfortran.dg/goacc/loop-tree-1.f90
@@ -44,4 +44,4 @@ end program test
 
 ! { dg-final { scan-tree-dump-times "private\\(m\\)" 1 "original" } } 
 ! { dg-final { scan-tree-dump-times "reduction\\(\\+:sum\\)" 1 "original" } } 
-! { dg-final { scan-tree-dump-times "map\\(tofrom:sum \\\[len: \[0-9\]+\\\]\\)" 1 "gimple" } }
+! { dg-final { scan-tree-dump-times "map\\(tofrom:sum \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 1 "gimple" } }
diff --git a/gcc/testsuite/gfortran.dg/goacc/private-explicit-kernels-1.f95 b/gcc/testsuite/gfortran.dg/goacc/private-explicit-kernels-1.f95
index 0c47045..fef5126 100644
--- a/gcc/testsuite/gfortran.dg/goacc/private-explicit-kernels-1.f95
+++ b/gcc/testsuite/gfortran.dg/goacc/private-explicit-kernels-1.f95
@@ -83,7 +83,7 @@ program test
   !$acc kernels ! Explicit "private(i2_2_s)" clause cannot be specified here.
   ! { dg-final { scan-tree-dump-times "private\\(i2_2_s\\)" 1 "original" { xfail *-*-* } } } ! PR90067
   ! { dg-final { scan-tree-dump-times "private\\(i2_2_s\\)" 1 "gimple" { xfail *-*-* } } } ! PR90067
-  ! { dg-final { scan-tree-dump-times "#pragma omp target oacc_kernels map\\(force_tofrom:i2_2_s \\\[len: \[0-9\]+\\\]\\)" 0 "gimple" { xfail *-*-* } } } ! PR90067
+  ! { dg-final { scan-tree-dump-times "#pragma omp target oacc_kernels map\\(force_tofrom:i2_2_s \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 0 "gimple" { xfail *-*-* } } } ! PR90067
   do i2_2_s = 1, 100
      !$acc loop private(j2_2_s) independent
      ! { dg-final { scan-tree-dump-times "#pragma acc loop private\\(j2_2_s\\) independent" 1 "original" } }
@@ -234,7 +234,7 @@ program test
   !$acc kernels ! Explicit "private(i3_5_s)" clause cannot be specified here.
   ! { dg-final { scan-tree-dump-times "private\\(i3_5_s\\)" 1 "original" { xfail *-*-* } } } ! PR90067
   ! { dg-final { scan-tree-dump-times "private\\(i3_5_s\\)" 1 "gimple" { xfail *-*-* } } } ! PR90067
-  ! { dg-final { scan-tree-dump-times "#pragma omp target oacc_kernels map\\(force_tofrom:i3_5_s \\\[len: \[0-9\]+\\\]\\)" 0 "gimple" { xfail *-*-* } } } ! PR90067
+  ! { dg-final { scan-tree-dump-times "#pragma omp target oacc_kernels map\\(force_tofrom:i3_5_s \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 0 "gimple" { xfail *-*-* } } } ! PR90067
   do i3_5_s = 1, 100
      !$acc loop private(j3_5_s) independent
      ! { dg-final { scan-tree-dump-times "#pragma acc loop private\\(j3_5_s\\) independent" 1 "original" } }
diff --git a/gcc/testsuite/gfortran.dg/goacc/private-predetermined-kernels-1.f95 b/gcc/testsuite/gfortran.dg/goacc/private-predetermined-kernels-1.f95
index 3357a20..38459cf 100644
--- a/gcc/testsuite/gfortran.dg/goacc/private-predetermined-kernels-1.f95
+++ b/gcc/testsuite/gfortran.dg/goacc/private-predetermined-kernels-1.f95
@@ -83,7 +83,7 @@ program test
   !$acc kernels
   ! { dg-final { scan-tree-dump-times "private\\(i2_2_s\\)" 1 "original" { xfail *-*-* } } } ! PR90067
   ! { dg-final { scan-tree-dump-times "private\\(i2_2_s\\)" 1 "gimple" { xfail *-*-* } } } ! PR90067
-  ! { dg-final { scan-tree-dump-times "#pragma omp target oacc_kernels map\\(force_tofrom:i2_2_s \\\[len: \[0-9\]+\\\]\\)" 0 "gimple" { xfail *-*-* } } } ! PR90067
+  ! { dg-final { scan-tree-dump-times "#pragma omp target oacc_kernels map\\(force_tofrom:i2_2_s \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 0 "gimple" { xfail *-*-* } } } ! PR90067
   do i2_2_s = 1, 100
      !$acc loop independent
      ! { dg-final { scan-tree-dump-times "#pragma acc loop private\\(j2_2_s\\) independent" 1 "original" } }
@@ -234,7 +234,7 @@ program test
   !$acc kernels
   ! { dg-final { scan-tree-dump-times "private\\(i3_5_s\\)" 1 "original" { xfail *-*-* } } } ! PR90067
   ! { dg-final { scan-tree-dump-times "private\\(i3_5_s\\)" 1 "gimple" { xfail *-*-* } } } ! PR90067
-  ! { dg-final { scan-tree-dump-times "#pragma omp target oacc_kernels map\\(force_tofrom:i3_5_s \\\[len: \[0-9\]+\\\]\\)" 0 "gimple" { xfail *-*-* } } } ! PR90067
+  ! { dg-final { scan-tree-dump-times "#pragma omp target oacc_kernels map\\(force_tofrom:i3_5_s \\\[len: \[0-9\]+\\\]\\\[implicit\\\]\\)" 0 "gimple" { xfail *-*-* } } } ! PR90067
   do i3_5_s = 1, 100
      !$acc loop independent
      ! { dg-final { scan-tree-dump-times "#pragma acc loop private\\(j3_5_s\\) independent" 1 "original" } }
diff --git a/gcc/tree-pretty-print.c b/gcc/tree-pretty-print.c
index 261cc9d..4cd4606 100644
--- a/gcc/tree-pretty-print.c
+++ b/gcc/tree-pretty-print.c
@@ -946,6 +946,9 @@ dump_omp_clause (pretty_printer *pp, tree clause, int spc, dump_flags_t flags)
 			     spc, flags, false);
 	  pp_right_bracket (pp);
 	}
+      if (OMP_CLAUSE_CODE (clause) == OMP_CLAUSE_MAP
+	  && OMP_CLAUSE_MAP_IMPLICIT_P (clause))
+	pp_string (pp, "[implicit]");
       pp_right_paren (pp);
       break;
 
diff --git a/gcc/tree.h b/gcc/tree.h
index 8d9829c..647c5ba 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1637,6 +1637,10 @@ class auto_suppress_location_wrappers
    variable.  */
 #define OMP_CLAUSE_MAP_IN_REDUCTION(NODE) \
   TREE_PRIVATE (OMP_CLAUSE_SUBCODE_CHECK (NODE, OMP_CLAUSE_MAP))
+/* Nonzero if this map clause was created through implicit data-mapping
+   rules. */
+#define OMP_CLAUSE_MAP_IMPLICIT_P(NODE) \
+  (OMP_CLAUSE_SUBCODE_CHECK (NODE, OMP_CLAUSE_MAP)->base.deprecated_flag)
 
 /* True on an OMP_CLAUSE_USE_DEVICE_PTR with an OpenACC 'if_present'
    clause.  */
diff --git a/include/gomp-constants.h b/include/gomp-constants.h
index b8efb30..33cfcb9 100644
--- a/include/gomp-constants.h
+++ b/include/gomp-constants.h
@@ -46,6 +46,16 @@
 					 | GOMP_MAP_FLAG_SPECIAL_0)
 #define GOMP_MAP_DEEP_COPY		(GOMP_MAP_FLAG_SPECIAL_4 \
 					 | GOMP_MAP_FLAG_SPECIAL_2)
+/* This value indicates the map was created implicitly according to
+   OpenMP rules.  */
+#define GOMP_MAP_IMPLICIT		(GOMP_MAP_FLAG_SPECIAL_3 \
+					 | GOMP_MAP_FLAG_SPECIAL_4)
+/* Mask for entire set of special map kind bits.  */
+#define GOMP_MAP_FLAG_SPECIAL_BITS	(GOMP_MAP_FLAG_SPECIAL_0 \
+					 | GOMP_MAP_FLAG_SPECIAL_1 \
+					 | GOMP_MAP_FLAG_SPECIAL_2 \
+					 | GOMP_MAP_FLAG_SPECIAL_3 \
+					 | GOMP_MAP_FLAG_SPECIAL_4)
 /* Flag to force a specific behavior (or else, trigger a run-time error).  */
 #define GOMP_MAP_FLAG_FORCE		(1 << 7)
 
@@ -225,7 +235,12 @@ enum gomp_map_kind
   (GOMP_MAP_ALWAYS_TO_P (X) || ((X) == GOMP_MAP_ALWAYS_FROM))
 
 #define GOMP_MAP_NONCONTIG_ARRAY_P(X) \
-  ((X) & GOMP_MAP_NONCONTIG_ARRAY)
+  (((X) & GOMP_MAP_FLAG_SPECIAL_BITS) == GOMP_MAP_NONCONTIG_ARRAY	\
+   || (X) == GOMP_MAP_NONCONTIG_ARRAY_FORCE_PRESENT)
+
+#define GOMP_MAP_IMPLICIT_P(X) \
+  (((X) & GOMP_MAP_FLAG_SPECIAL_BITS) == GOMP_MAP_IMPLICIT)
+
 
 /* Asynchronous behavior.  Keep in sync with
    libgomp/{openacc.h,openacc.f90,openacc_lib.h}:acc_async_t.  */
diff --git a/libgomp/target.c b/libgomp/target.c
index 9c75826..ecda2ef 100644
--- a/libgomp/target.c
+++ b/libgomp/target.c
@@ -510,7 +510,7 @@ static inline void
 gomp_map_vars_existing (struct gomp_device_descr *devicep,
 			struct goacc_asyncqueue *aq, splay_tree_key oldn,
 			splay_tree_key newn, struct target_var_desc *tgt_var,
-			unsigned char kind, bool always_to_flag,
+			unsigned char kind, bool always_to_flag, bool implicit,
 			struct gomp_coalesce_buf *cbuf,
 			htab_t *refcount_set)
 {
@@ -522,11 +522,22 @@ gomp_map_vars_existing (struct gomp_device_descr *devicep,
   tgt_var->always_copy_from = GOMP_MAP_ALWAYS_FROM_P (kind);
   tgt_var->is_attach = false;
   tgt_var->offset = newn->host_start - oldn->host_start;
-  tgt_var->length = newn->host_end - newn->host_start;
+
+  /* For implicit maps, old contained in new is valid.  */
+  bool implicit_subset = (implicit
+			  && newn->host_start <= oldn->host_start
+			  && oldn->host_end <= newn->host_end);
+  if (implicit_subset)
+    tgt_var->length = oldn->host_end - oldn->host_start;
+  else
+    tgt_var->length = newn->host_end - newn->host_start;
 
   if ((kind & GOMP_MAP_FLAG_FORCE)
-      || oldn->host_start > newn->host_start
-      || oldn->host_end < newn->host_end)
+      /* For implicit maps, old contained in new is valid.  */
+      || !(implicit_subset
+	   /* Otherwise, new contained inside old is considered valid.  */
+	   || (oldn->host_start <= newn->host_start
+	       && newn->host_end <= oldn->host_end)))
     {
       gomp_mutex_unlock (&devicep->lock);
       gomp_fatal ("Trying to map into device [%p..%p) object when "
@@ -536,11 +547,17 @@ gomp_map_vars_existing (struct gomp_device_descr *devicep,
     }
 
   if (GOMP_MAP_ALWAYS_TO_P (kind) || always_to_flag)
-    gomp_copy_host2dev (devicep, aq,
-			(void *) (oldn->tgt->tgt_start + oldn->tgt_offset
-				  + newn->host_start - oldn->host_start),
-			(void *) newn->host_start,
-			newn->host_end - newn->host_start, false, cbuf);
+    {
+      /* Implicit + always should not happen. If this does occur, below
+	 address/length adjustment is a TODO.  */
+      assert (!implicit_subset);
+
+      gomp_copy_host2dev (devicep, aq,
+			  (void *) (oldn->tgt->tgt_start + oldn->tgt_offset
+				    + newn->host_start - oldn->host_start),
+			  (void *) newn->host_start,
+			  newn->host_end - newn->host_start, false, cbuf);
+    }
 
   gomp_increment_refcount (oldn, refcount_set);
 }
@@ -548,8 +565,24 @@ gomp_map_vars_existing (struct gomp_device_descr *devicep,
 static int
 get_kind (bool short_mapkind, void *kinds, int idx)
 {
-  return short_mapkind ? ((unsigned short *) kinds)[idx]
-		       : ((unsigned char *) kinds)[idx];
+  int val = (short_mapkind
+	     ? ((unsigned short *) kinds)[idx]
+	     : ((unsigned char *) kinds)[idx]);
+
+  if (GOMP_MAP_IMPLICIT_P (val))
+    val &= ~GOMP_MAP_IMPLICIT;
+  return val;
+}
+
+
+static bool
+get_implicit (bool short_mapkind, void *kinds, int idx)
+{
+  int val = (short_mapkind
+	     ? ((unsigned short *) kinds)[idx]
+	     : ((unsigned char *) kinds)[idx]);
+
+  return GOMP_MAP_IMPLICIT_P (val);
 }
 
 static void
@@ -612,6 +645,7 @@ gomp_map_fields_existing (struct target_mem_desc *tgt,
   struct splay_tree_s *mem_map = &devicep->mem_map;
   struct splay_tree_key_s cur_node;
   int kind;
+  bool implicit;
   const bool short_mapkind = true;
   const int typemask = short_mapkind ? 0xff : 0x7;
 
@@ -619,12 +653,14 @@ gomp_map_fields_existing (struct target_mem_desc *tgt,
   cur_node.host_end = cur_node.host_start + sizes[i];
   splay_tree_key n2 = splay_tree_lookup (mem_map, &cur_node);
   kind = get_kind (short_mapkind, kinds, i);
+  implicit = get_implicit (short_mapkind, kinds, i);
   if (n2
       && n2->tgt == n->tgt
       && n2->host_start - n->host_start == n2->tgt_offset - n->tgt_offset)
     {
       gomp_map_vars_existing (devicep, aq, n2, &cur_node, &tgt->list[i],
-			      kind & typemask, false, cbuf, refcount_set);
+			      kind & typemask, false, implicit, cbuf,
+			      refcount_set);
       return;
     }
   if (sizes[i] == 0)
@@ -640,7 +676,8 @@ gomp_map_fields_existing (struct target_mem_desc *tgt,
 		 == n2->tgt_offset - n->tgt_offset)
 	    {
 	      gomp_map_vars_existing (devicep, aq, n2, &cur_node, &tgt->list[i],
-				      kind & typemask, false, cbuf, refcount_set);
+				      kind & typemask, false, implicit, cbuf,
+				      refcount_set);
 	      return;
 	    }
 	}
@@ -652,7 +689,8 @@ gomp_map_fields_existing (struct target_mem_desc *tgt,
 	  && n2->host_start - n->host_start == n2->tgt_offset - n->tgt_offset)
 	{
 	  gomp_map_vars_existing (devicep, aq, n2, &cur_node, &tgt->list[i],
-				  kind & typemask, false, cbuf, refcount_set);
+				  kind & typemask, false, implicit, cbuf,
+				  refcount_set);
 	  return;
 	}
     }
@@ -898,6 +936,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
   for (i = 0; i < mapnum; i++)
     {
       int kind = get_kind (short_mapkind, kinds, i);
+      bool implicit = get_implicit (short_mapkind, kinds, i);
       if (hostaddrs[i] == NULL
 	  || (kind & typemask) == GOMP_MAP_FIRSTPRIVATE_INT)
 	{
@@ -1104,8 +1143,8 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
 		}
 	    }
 	  gomp_map_vars_existing (devicep, aq, n, &cur_node, &tgt->list[i],
-				  kind & typemask, always_to_cnt > 0, NULL,
-				  refcount_set);
+				  kind & typemask, always_to_cnt > 0, implicit,
+				  NULL, refcount_set);
 	  i += always_to_cnt;
 	}
       else
@@ -1182,7 +1221,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
 		{
 		  assert (n->refcount != REFCOUNT_LINK);
 		  gomp_map_vars_existing (devicep, aq, n, &cur_node, row_desc,
-					  kind & typemask, false,
+					  kind & typemask, false, false,
 					  /* TODO: cbuf? */ NULL, refcount_set);
 		}
 	      else
@@ -1312,6 +1351,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
 	else if (tgt->list[i].key == NULL)
 	  {
 	    int kind = get_kind (short_mapkind, kinds, i);
+	    bool implicit = get_implicit (short_mapkind, kinds, i);
 	    if (hostaddrs[i] == NULL)
 	      continue;
 	    switch (kind & typemask)
@@ -1483,7 +1523,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
 	    splay_tree_key n = splay_tree_lookup (mem_map, k);
 	    if (n && n->refcount != REFCOUNT_LINK)
 	      gomp_map_vars_existing (devicep, aq, n, k, &tgt->list[i],
-				      kind & typemask, false, cbufp,
+				      kind & typemask, false, implicit, cbufp,
 				      refcount_set);
 	    else
 	      {
@@ -1702,7 +1742,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
 		    {
 		      assert (k->refcount != REFCOUNT_LINK);
 		      gomp_map_vars_existing (devicep, aq, k, &cur_node, row_desc,
-					      kind & typemask, false,
+					      kind & typemask, false, false,
 					      cbufp, refcount_set);
 		    }
 		  else
diff --git a/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-1.c b/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-1.c
new file mode 100644
index 0000000..f2e7293
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-1.c
@@ -0,0 +1,31 @@
+#ifdef __cplusplus
+extern "C"
+#else
+extern
+#endif
+void abort (void);
+
+int
+main (void)
+{
+  #define N 5
+  int array[N][N];
+
+  for (int i = 0; i < N; i++)
+    {
+      #pragma omp target enter data map(alloc: array[i:1][0:N])
+
+      #pragma omp target
+      for (int j = 0; j < N; j++)
+	array[i][j] = i + j;
+
+      #pragma omp target exit data map(from: array[i:1][0:N])
+    }
+
+  for (int i = 0; i < N; i++)
+    for (int j = 0; j < N; j++)
+      if (array[i][j] != i + j)
+	abort ();
+
+  return 0;
+}
