#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 *
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,
{
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);
/* 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));
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. */
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);
}
}
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