Re: [gomp4] Add tables generation

[Bernd Schmidt]

On 04/02/2014 10:36 AM, Thomas Schwinge wrote:
I see regressions in the libgomp testsuite for configurations where
offloading is not enabled:
     spawn [...]/build/gcc/xgcc -B[...]/build/gcc/ 
[...]/source/libgomp/testsuite/libgomp.c/for-3.c 
-B[...]/build/x86_64-unknown-linux-gnu/./libgomp/ 
-B[...]/build/x86_64-unknown-linux-gnu/./libgomp/.libs 
-I[...]/build/x86_64-unknown-linux-gnu/./libgomp 
-I[...]/source/libgomp/testsuite/.. -fmessage-length=0 
-fno-diagnostics-show-caret -fdiagnostics-color=never -fopenmp -std=gnu99 
-fopenmp -L[...]/build/x86_64-unknown-linux-gnu/./libgomp/.libs -lm -o 
./for-3.exe
     /tmp/ccGnT0ei.o: In function `main':
     for-3.c:(.text+0x21032): undefined reference to `__OPENMP_TARGET__'
     collect2: error: ld returned 1 exit status

I suppose that's because [...]

Workaround committed in r209015:

        libgcc/
        * crtstuff.c [!ENABLE_OFFLOADING] (__OPENMP_TARGET__): Define to
        NULL.

The patch below should be a better fix, making the references to 
__OPENMP_TARGET__ weak. Does this work for you?


Bernd

Index: gcc/omp-low.c
===================================================================
--- gcc/omp-low.c	(revision 429741)
+++ gcc/omp-low.c	(working copy)
@@ -221,6 +221,28 @@ static tree scan_omp_1_op (tree *, int *
       *handled_ops_p = false; \
       break;
 
+static GTY(()) tree offload_symbol_decl;
+
+/* Get the __OPENMP_TARGET__ symbol.  */
+static tree
+get_offload_symbol_decl (void)
+{
+  if (!offload_symbol_decl)
+    {
+      tree decl = build_decl (UNKNOWN_LOCATION, VAR_DECL,
+			      get_identifier ("__OPENMP_TARGET__"),
+			      ptr_type_node);
+      TREE_PUBLIC (decl) = 1;
+      DECL_EXTERNAL (decl) = 1;
+      DECL_WEAK (decl) = 1;
+      DECL_ATTRIBUTES (decl)
+	= tree_cons (get_identifier ("weak"),
+		     NULL_TREE, DECL_ATTRIBUTES (decl));
+      offload_symbol_decl = decl;
+    }
+  return offload_symbol_decl;
+}
+
 /* Convenience function for calling scan_omp_1_op on tree operands.  */
 
 static inline tree
@@ -5148,11 +5170,7 @@ expand_oacc_offload (struct omp_region *
     }
 
   gimple g;
-  tree openmp_target
-    = build_decl (UNKNOWN_LOCATION, VAR_DECL,
-		  get_identifier ("__OPENMP_TARGET__"), ptr_type_node);
-  TREE_PUBLIC (openmp_target) = 1;
-  DECL_EXTERNAL (openmp_target) = 1;
+  tree openmp_target = get_offload_symbol_decl ();
   tree fnaddr = build_fold_addr_expr (child_fn);
   g = gimple_build_call (builtin_decl_explicit (start_ix), 10, device,
 			 fnaddr, build_fold_addr_expr (openmp_target),
@@ -8686,11 +8704,7 @@ expand_omp_target (struct omp_region *re
     }
 
   gimple g;
-  tree openmp_target
-    = build_decl (UNKNOWN_LOCATION, VAR_DECL,
-		  get_identifier ("__OPENMP_TARGET__"), ptr_type_node);
-  TREE_PUBLIC (openmp_target) = 1;
-  DECL_EXTERNAL (openmp_target) = 1;
+  tree openmp_target = get_offload_symbol_decl ();
   if (kind == GF_OMP_TARGET_KIND_REGION)
     {
       tree fnaddr = build_fold_addr_expr (child_fn);