nvptx.c (global_lock_var): New.

	gcc/
	* config/nvptx/nvptx.c (global_lock_var): New.
	(nvptx_global_lock_addr): New.
	(nvptx_lockless_update): Recomment and adjust for clarity.
	(nvptx_lockfull_update): New.
	(nvptx_reduction_update): New.
	(nvptx_goacc_reduction_fini): Call it.

	libgcc/
	* config/nvptx/reduction.c: New.
	* config/nvptx/t-nvptx (LIB2ADD): Add it.

	libgomp/
	* testsuite/libgomp.oacc-c-c++-common/reduction-cplx-flt.c: Add
	worker & gang cases.
	* testsuite/libgomp.oacc-c-c++-common/reduction-cplx-dbl.c: Likewise.

From-SVN: r230545

1 files changed, 201 insertions, 39 deletions

diff --git a/gcc/config/nvptx/nvptx.c b/gcc/config/nvptx/nvptx.c
index 26c2e96..4436ac4 100644
--- a/gcc/config/nvptx/nvptx.c
+++ b/gcc/config/nvptx/nvptx.c
@@ -114,6 +114,9 @@ static unsigned worker_red_align;
 #define worker_red_name "__worker_red"
 static GTY(()) rtx worker_red_sym;
 
+/* Global lock variable, needed for 128bit worker & gang reductions.  */
+static GTY(()) tree global_lock_var;
+
 /* Allocate a new, cleared machine_function structure.  */
 
 static struct machine_function *
@@ -3681,8 +3684,45 @@ nvptx_generate_vector_shuffle (location_t loc,
   gimplify_assign (dest_var, expr, seq);
 }
 
-/* Insert code to locklessly update  *PTR with *PTR OP VAR just before
-   GSI.  */
+/* Lazily generate the global lock var decl and return its address.  */
+
+static tree
+nvptx_global_lock_addr ()
+{
+  tree v = global_lock_var;
+  
+  if (!v)
+    {
+      tree name = get_identifier ("__reduction_lock");
+      tree type = build_qualified_type (unsigned_type_node,
+					TYPE_QUAL_VOLATILE);
+      v = build_decl (BUILTINS_LOCATION, VAR_DECL, name, type);
+      global_lock_var = v;
+      DECL_ARTIFICIAL (v) = 1;
+      DECL_EXTERNAL (v) = 1;
+      TREE_STATIC (v) = 1;
+      TREE_PUBLIC (v) = 1;
+      TREE_USED (v) = 1;
+      mark_addressable (v);
+      mark_decl_referenced (v);
+    }
+
+  return build_fold_addr_expr (v);
+}
+
+/* Insert code to locklessly update *PTR with *PTR OP VAR just before
+   GSI.  We use a lockless scheme for nearly all case, which looks
+   like:
+     actual = initval(OP);
+     do {
+       guess = actual;
+       write = guess OP myval;
+       actual = cmp&swap (ptr, guess, write)
+     } while (actual bit-different-to guess);
+   return write;
+
+   This relies on a cmp&swap instruction, which is available for 32-
+   and 64-bit types.  Larger types must use a locking scheme.  */
 
 static tree
 nvptx_lockless_update (location_t loc, gimple_stmt_iterator *gsi,
@@ -3690,46 +3730,30 @@ nvptx_lockless_update (location_t loc, gimple_stmt_iterator *gsi,
 {
   unsigned fn = NVPTX_BUILTIN_CMP_SWAP;
   tree_code code = NOP_EXPR;
-  tree type = unsigned_type_node;
-
-  enum machine_mode mode = TYPE_MODE (TREE_TYPE (var));
+  tree arg_type = unsigned_type_node;
+  tree var_type = TREE_TYPE (var);
 
-  if (!INTEGRAL_MODE_P (mode))
+  if (TREE_CODE (var_type) == COMPLEX_TYPE
+      || TREE_CODE (var_type) == REAL_TYPE)
     code = VIEW_CONVERT_EXPR;
-  if (GET_MODE_SIZE (mode) == GET_MODE_SIZE (DImode))
+
+  if (TYPE_SIZE (var_type) == TYPE_SIZE (long_long_unsigned_type_node))
     {
+      arg_type = long_long_unsigned_type_node;
       fn = NVPTX_BUILTIN_CMP_SWAPLL;
-      type = long_long_unsigned_type_node;
     }
 
+  tree swap_fn = nvptx_builtin_decl (fn, true);
+
   gimple_seq init_seq = NULL;
-  tree init_var = make_ssa_name (type);
-  tree init_expr = omp_reduction_init_op (loc, op, TREE_TYPE (var));
-  init_expr = fold_build1 (code, type, init_expr);
+  tree init_var = make_ssa_name (arg_type);
+  tree init_expr = omp_reduction_init_op (loc, op, var_type);
+  init_expr = fold_build1 (code, arg_type, init_expr);
   gimplify_assign (init_var, init_expr, &init_seq);
   gimple *init_end = gimple_seq_last (init_seq);
 
   gsi_insert_seq_before (gsi, init_seq, GSI_SAME_STMT);
   
-  gimple_seq loop_seq = NULL;
-  tree expect_var = make_ssa_name (type);
-  tree actual_var = make_ssa_name (type);
-  tree write_var = make_ssa_name (type);
-  
-  tree write_expr = fold_build1 (code, TREE_TYPE (var), expect_var);
-  write_expr = fold_build2 (op, TREE_TYPE (var), write_expr, var);
-  write_expr = fold_build1 (code, type, write_expr);
-  gimplify_assign (write_var, write_expr, &loop_seq);
-
-  tree swap_expr = nvptx_builtin_decl (fn, true);
-  swap_expr = build_call_expr_loc (loc, swap_expr, 3,
-				   ptr, expect_var, write_var);
-  gimplify_assign (actual_var, swap_expr, &loop_seq);
-
-  gcond *cond = gimple_build_cond (EQ_EXPR, actual_var, expect_var,
-				   NULL_TREE, NULL_TREE);
-  gimple_seq_add_stmt (&loop_seq, cond);
-
   /* Split the block just after the init stmts.  */
   basic_block pre_bb = gsi_bb (*gsi);
   edge pre_edge = split_block (pre_bb, init_end);
@@ -3738,12 +3762,34 @@ nvptx_lockless_update (location_t loc, gimple_stmt_iterator *gsi,
   /* Reset the iterator.  */
   *gsi = gsi_for_stmt (gsi_stmt (*gsi));
 
-  /* Insert the loop statements.  */
-  gimple *loop_end = gimple_seq_last (loop_seq);
-  gsi_insert_seq_before (gsi, loop_seq, GSI_SAME_STMT);
+  tree expect_var = make_ssa_name (arg_type);
+  tree actual_var = make_ssa_name (arg_type);
+  tree write_var = make_ssa_name (arg_type);
+  
+  /* Build and insert the reduction calculation.  */
+  gimple_seq red_seq = NULL;
+  tree write_expr = fold_build1 (code, var_type, expect_var);
+  write_expr = fold_build2 (op, var_type, write_expr, var);
+  write_expr = fold_build1 (code, arg_type, write_expr);
+  gimplify_assign (write_var, write_expr, &red_seq);
+
+  gsi_insert_seq_before (gsi, red_seq, GSI_SAME_STMT);
+
+  /* Build & insert the cmp&swap sequence.  */
+  gimple_seq latch_seq = NULL;
+  tree swap_expr = build_call_expr_loc (loc, swap_fn, 3,
+					ptr, expect_var, write_var);
+  gimplify_assign (actual_var, swap_expr, &latch_seq);
+
+  gcond *cond = gimple_build_cond (EQ_EXPR, actual_var, expect_var,
+				   NULL_TREE, NULL_TREE);
+  gimple_seq_add_stmt (&latch_seq, cond);
+
+  gimple *latch_end = gimple_seq_last (latch_seq);
+  gsi_insert_seq_before (gsi, latch_seq, GSI_SAME_STMT);
 
-  /* Split the block just after the loop stmts.  */
-  edge post_edge = split_block (loop_bb, loop_end);
+  /* Split the block just after the latch stmts.  */
+  edge post_edge = split_block (loop_bb, latch_end);
   basic_block post_bb = post_edge->dest;
   loop_bb = post_edge->src;
   *gsi = gsi_for_stmt (gsi_stmt (*gsi));
@@ -3762,7 +3808,123 @@ nvptx_lockless_update (location_t loc, gimple_stmt_iterator *gsi,
   loop->latch = loop_bb;
   add_loop (loop, loop_bb->loop_father);
 
-  return fold_build1 (code, TREE_TYPE (var), write_var);
+  return fold_build1 (code, var_type, write_var);
+}
+
+/* Insert code to lockfully update *PTR with *PTR OP VAR just before
+   GSI.  This is necessary for types larger than 64 bits, where there
+   is no cmp&swap instruction to implement a lockless scheme.  We use
+   a lock variable in global memory.
+
+   while (cmp&swap (&lock_var, 0, 1))
+     continue;
+   T accum = *ptr;
+   accum = accum OP var;
+   *ptr = accum;
+   cmp&swap (&lock_var, 1, 0);
+   return accum;
+
+   A lock in global memory is necessary to force execution engine
+   descheduling and avoid resource starvation that can occur if the
+   lock is in .shared memory.  */
+
+static tree
+nvptx_lockfull_update (location_t loc, gimple_stmt_iterator *gsi,
+		       tree ptr, tree var, tree_code op)
+{
+  tree var_type = TREE_TYPE (var);
+  tree swap_fn = nvptx_builtin_decl (NVPTX_BUILTIN_CMP_SWAP, true);
+  tree uns_unlocked = build_int_cst (unsigned_type_node, 0);
+  tree uns_locked = build_int_cst (unsigned_type_node, 1);
+
+  /* Split the block just before the gsi.  Insert a gimple nop to make
+     this easier.  */
+  gimple *nop = gimple_build_nop ();
+  gsi_insert_before (gsi, nop, GSI_SAME_STMT);
+  basic_block entry_bb = gsi_bb (*gsi);
+  edge entry_edge = split_block (entry_bb, nop);
+  basic_block lock_bb = entry_edge->dest;
+  /* Reset the iterator.  */
+  *gsi = gsi_for_stmt (gsi_stmt (*gsi));
+
+  /* Build and insert the locking sequence.  */
+  gimple_seq lock_seq = NULL;
+  tree lock_var = make_ssa_name (unsigned_type_node);
+  tree lock_expr = nvptx_global_lock_addr ();
+  lock_expr = build_call_expr_loc (loc, swap_fn, 3, lock_expr,
+				   uns_unlocked, uns_locked);
+  gimplify_assign (lock_var, lock_expr, &lock_seq);
+  gcond *cond = gimple_build_cond (EQ_EXPR, lock_var, uns_unlocked,
+				   NULL_TREE, NULL_TREE);
+  gimple_seq_add_stmt (&lock_seq, cond);
+  gimple *lock_end = gimple_seq_last (lock_seq);
+  gsi_insert_seq_before (gsi, lock_seq, GSI_SAME_STMT);
+
+  /* Split the block just after the lock sequence.  */
+  edge locked_edge = split_block (lock_bb, lock_end);
+  basic_block update_bb = locked_edge->dest;
+  lock_bb = locked_edge->src;
+  *gsi = gsi_for_stmt (gsi_stmt (*gsi));
+  
+  /* Create the lock loop ... */
+  locked_edge->flags ^= EDGE_TRUE_VALUE | EDGE_FALLTHRU;
+  make_edge (lock_bb, lock_bb, EDGE_FALSE_VALUE);
+  set_immediate_dominator (CDI_DOMINATORS, lock_bb, entry_bb);
+  set_immediate_dominator (CDI_DOMINATORS, update_bb, lock_bb);
+
+  /* ... and the loop structure.  */
+  loop *lock_loop = alloc_loop ();
+  lock_loop->header = lock_bb;
+  lock_loop->latch = lock_bb;
+  lock_loop->nb_iterations_estimate = 1;
+  lock_loop->any_estimate = true;
+  add_loop (lock_loop, entry_bb->loop_father);
+
+  /* Build and insert the reduction calculation.  */
+  gimple_seq red_seq = NULL;
+  tree acc_in = make_ssa_name (var_type);
+  tree ref_in = build_simple_mem_ref (ptr);
+  TREE_THIS_VOLATILE (ref_in) = 1;
+  gimplify_assign (acc_in, ref_in, &red_seq);
+  
+  tree acc_out = make_ssa_name (var_type);
+  tree update_expr = fold_build2 (op, var_type, ref_in, var);
+  gimplify_assign (acc_out, update_expr, &red_seq);
+  
+  tree ref_out = build_simple_mem_ref (ptr);
+  TREE_THIS_VOLATILE (ref_out) = 1;
+  gimplify_assign (ref_out, acc_out, &red_seq);
+
+  gsi_insert_seq_before (gsi, red_seq, GSI_SAME_STMT);
+
+  /* Build & insert the unlock sequence.  */
+  gimple_seq unlock_seq = NULL;
+  tree unlock_expr = nvptx_global_lock_addr ();
+  unlock_expr = build_call_expr_loc (loc, swap_fn, 3, unlock_expr,
+				     uns_locked, uns_unlocked);
+  gimplify_and_add (unlock_expr, &unlock_seq);
+  gsi_insert_seq_before (gsi, unlock_seq, GSI_SAME_STMT);
+
+  return acc_out;
+}
+
+/* Emit a sequence to update a reduction accumlator at *PTR with the
+   value held in VAR using operator OP.  Return the updated value.
+
+   TODO: optimize for atomic ops and indepedent complex ops.  */
+
+static tree
+nvptx_reduction_update (location_t loc, gimple_stmt_iterator *gsi,
+			tree ptr, tree var, tree_code op)
+{
+  tree type = TREE_TYPE (var);
+  tree size = TYPE_SIZE (type);
+
+  if (size == TYPE_SIZE (unsigned_type_node)
+      || size == TYPE_SIZE (long_long_unsigned_type_node))
+    return nvptx_lockless_update (loc, gsi, ptr, var, op);
+  else
+    return nvptx_lockfull_update (loc, gsi, ptr, var, op);
 }
 
 /* NVPTX implementation of GOACC_REDUCTION_SETUP.  */
@@ -3944,11 +4106,11 @@ nvptx_goacc_reduction_fini (gcall *call)
 
       if (accum)
 	{
-	  /* Locklessly update the accumulator.  */
+	  /* UPDATE the accumulator.  */
 	  gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
 	  seq = NULL;
-	  r = nvptx_lockless_update (gimple_location (call), &gsi,
-				     accum, var, op);
+	  r = nvptx_reduction_update (gimple_location (call), &gsi,
+				      accum, var, op);
 	}
     }