Re: [patch] various OpenACC reduction enhancements - ME and nvptx changes

[Cesar Philippidis <cesar at codesourcery dot com>]

The attached patch includes the nvptx and GCC ME reductions enhancements.

Is this patch OK for trunk? It bootstrapped / regression tested cleanly
for x86_64 with nvptx offloading.

Thanks,
Cesar

2018-06-29  Cesar Philippidis  <cesar@codesourcery.com>
	    Nathan Sidwell  <nathan@acm.org>

	gcc/
	* config/nvptx/nvptx.c (nvptx_propagate_unified): New.
	(nvptx_split_blocks): Call it for cond_uni insn.
	(nvptx_expand_cond_uni): New.
	(enum nvptx_builtins): Add NVPTX_BUILTIN_COND_UNI.
	(nvptx_init_builtins): Initialize it.
	(nvptx_expand_builtin):
	(nvptx_generate_vector_shuffle): Change integral SHIFT operand to
	tree BITS operand.
	(nvptx_vector_reduction): New.
	(nvptx_adjust_reduction_type): New.
	(nvptx_goacc_reduction_setup): Use it to adjust the type of ref_to_res.
	(nvptx_goacc_reduction_init): Don't update LHS if it doesn't exist.
	(nvptx_goacc_reduction_fini): Call nvptx_vector_reduction for vector.
	Use it to adjust the type of ref_to_res.
	(nvptx_goacc_reduction_teardown):
	* config/nvptx/nvptx.md (cond_uni): New pattern.
	* omp-general.h (enum oacc_loop_flags): Add OLF_REDUCTION enum.
	* omp-low.c (lower_oacc_reductions): Handle reduction decls mapped
	with GOMP_MAP_FIRSTPRIVATE_POINTER.
	(lower_oacc_head_mark): Use OLF_REDUCTION to mark OpenACC reductions.
	* omp-offload.c (oacc_loop_auto_partitions): Don't assign gang
	level parallelism to orphan reductions.
	(default_goacc_reduction): Retype ref_to_res as necessary.

---
diff --git a/gcc/config/nvptx/nvptx.c b/gcc/config/nvptx/nvptx.c
index 5608bee8a8d..33ec3db1153 100644
--- a/gcc/config/nvptx/nvptx.c
+++ b/gcc/config/nvptx/nvptx.c
@@ -2863,6 +2863,52 @@ nvptx_reorg_uniform_simt ()
     }
 }
 
+/* UNIFIED is a cond_uni insn.  Find the branch insn it affects, and
+   mark that as unified.  We expect to be in a single block.  */
+
+static void
+nvptx_propagate_unified (rtx_insn *unified)
+{
+  rtx_insn *probe = unified;
+  rtx cond_reg = SET_DEST (PATTERN (unified));
+  rtx pat = NULL_RTX;
+
+  /* Find the comparison.  (We could skip this and simply scan to he
+     blocks' terminating branch, if we didn't care for self
+     checking.)  */
+  for (;;)
+    {
+      probe = next_real_insn (probe);
+      if (!probe)
+	break;
+      pat = PATTERN (probe);
+
+      if (GET_CODE (pat) == SET
+	  && GET_RTX_CLASS (GET_CODE (SET_SRC (pat))) == RTX_COMPARE
+	  && XEXP (SET_SRC (pat), 0) == cond_reg)
+	break;
+      gcc_assert (NONJUMP_INSN_P (probe));
+    }
+  gcc_assert (pat);
+  rtx pred_reg = SET_DEST (pat);
+
+  /* Find the branch.  */
+  do
+    probe = NEXT_INSN (probe);
+  while (!JUMP_P (probe));
+
+  pat = PATTERN (probe);
+  rtx itec = XEXP (SET_SRC (pat), 0);
+  gcc_assert (XEXP (itec, 0) == pred_reg);
+
+  /* Mark the branch's condition as unified.  */
+  rtx unspec = gen_rtx_UNSPEC (BImode, gen_rtvec (1, pred_reg),
+			       UNSPEC_BR_UNIFIED);
+  bool ok = validate_change (probe, &XEXP (itec, 0), unspec, false);
+
+  gcc_assert (ok);
+}
+
 /* Loop structure of the function.  The entire function is described as
    a NULL loop.  */
 
@@ -2964,6 +3010,9 @@ nvptx_split_blocks (bb_insn_map_t *map)
 	    continue;
 	  switch (recog_memoized (insn))
 	    {
+	    case CODE_FOR_cond_uni:
+	      nvptx_propagate_unified (insn);
+	      /* FALLTHROUGH */
 	    default:
 	      seen_insn = true;
 	      continue;
@@ -5080,6 +5129,21 @@ nvptx_expand_cmp_swap (tree exp, rtx target,
   return target;
 }
 
+/* Expander for the compare unified builtin.  */
+
+static rtx
+nvptx_expand_cond_uni (tree exp, rtx target, machine_mode mode, int ignore)
+{
+  if (ignore)
+    return target;
+  
+  rtx src = expand_expr (CALL_EXPR_ARG (exp, 0),
+			 NULL_RTX, mode, EXPAND_NORMAL);
+
+  emit_insn (gen_cond_uni (target, src));
+
+  return target;
+}
 
 /* Codes for all the NVPTX builtins.  */
 enum nvptx_builtins
@@ -5089,6 +5153,7 @@ enum nvptx_builtins
   NVPTX_BUILTIN_WORKER_ADDR,
   NVPTX_BUILTIN_CMP_SWAP,
   NVPTX_BUILTIN_CMP_SWAPLL,
+  NVPTX_BUILTIN_COND_UNI,
   NVPTX_BUILTIN_MAX
 };
 
@@ -5126,6 +5191,7 @@ nvptx_init_builtins (void)
        (PTRVOID, ST, UINT, UINT, NULL_TREE));
   DEF (CMP_SWAP, "cmp_swap", (UINT, PTRVOID, UINT, UINT, NULL_TREE));
   DEF (CMP_SWAPLL, "cmp_swapll", (LLUINT, PTRVOID, LLUINT, LLUINT, NULL_TREE));
+  DEF (COND_UNI, "cond_uni", (integer_type_node, integer_type_node, NULL_TREE));
 
 #undef DEF
 #undef ST
@@ -5158,6 +5224,9 @@ nvptx_expand_builtin (tree exp, rtx target, rtx ARG_UNUSED (subtarget),
     case NVPTX_BUILTIN_CMP_SWAPLL:
       return nvptx_expand_cmp_swap (exp, target, mode, ignore);
 
+    case NVPTX_BUILTIN_COND_UNI:
+      return nvptx_expand_cond_uni (exp, target, mode, ignore);
+
     default: gcc_unreachable ();
     }
 }
@@ -5284,7 +5353,7 @@ nvptx_get_worker_red_addr (tree type, tree offset)
 
 static void
 nvptx_generate_vector_shuffle (location_t loc,
-			       tree dest_var, tree var, unsigned shift,
+			       tree dest_var, tree var, tree bits,
 			       gimple_seq *seq)
 {
   unsigned fn = NVPTX_BUILTIN_SHUFFLE;
@@ -5307,7 +5376,6 @@ nvptx_generate_vector_shuffle (location_t loc,
     }
   
   tree call = nvptx_builtin_decl (fn, true);
-  tree bits = build_int_cst (unsigned_type_node, shift);
   tree kind = build_int_cst (unsigned_type_node, SHUFFLE_DOWN);
   tree expr;
 
@@ -5583,6 +5651,126 @@ nvptx_reduction_update (location_t loc, gimple_stmt_iterator *gsi,
     return nvptx_lockfull_update (loc, gsi, ptr, var, op);
 }
 
+/* Emit a vector-level reduction loop.  OLD_VAR is the incoming
+   variable to reduce (valid in each vector), OP is the reduction
+   operator.  Return the reduced value (an SSA var).
+
+   The code we generate looks like:
+      unsigned old_shift = DIM_SIZE(VECTOR);
+      do 
+	{
+	  shift = PHI (old_shift, new_shift);
+	  var = PHI (old_var, new_var);
+	  new_shift = shift >> 1;
+	  other_var = VSHUFFLE (var, new_shift);
+	  new_var = var OP other_var;
+	  cond_var = builtin_cond_uni (new_shift);
+	}
+	while (cond_var > 1);
+
+  The builtin_cond_ini expands to a cond_uni instruction, which is
+  processed in nvpts_split_blocks to mark the loop's terminating
+  branch instruction.  */
+
+static tree
+nvptx_vector_reduction (location_t loc, gimple_stmt_iterator *gsi,
+			tree old_var, tree_code op)
+{
+  tree var_type = TREE_TYPE (old_var);
+
+  /*  Emit old_shift = DIM_SIZE(VECTOR) */
+  tree old_shift = make_ssa_name (integer_type_node);
+  tree dim = build_int_cst (integer_type_node, GOMP_DIM_VECTOR);
+  gcall *call = gimple_build_call_internal (IFN_GOACC_DIM_SIZE, 1, dim);
+  gimple_set_lhs (call, old_shift);
+  gimple_set_location (call, loc);
+  gsi_insert_before (gsi, call, GSI_SAME_STMT);
+
+  /* Split the block just after the init stmts.  */
+  basic_block pre_bb = gsi_bb (*gsi);
+  edge pre_edge = split_block (pre_bb, call);
+  basic_block loop_bb = pre_edge->dest;
+  pre_bb = pre_edge->src;
+  /* Reset the iterator.  */
+  *gsi = gsi_for_stmt (gsi_stmt (*gsi));
+
+  tree shift = make_ssa_name (integer_type_node);
+  tree new_shift = make_ssa_name (integer_type_node);
+  tree var = make_ssa_name (var_type);
+  tree other_var = make_ssa_name (var_type);
+  tree new_var = make_ssa_name (var_type);
+  
+  /* Build and insert the loop body.  */
+  gimple_seq loop_seq = NULL;
+
+  /* new_shift = shift >> 1 */
+  tree shift_expr = fold_build2 (RSHIFT_EXPR, integer_type_node,
+				 shift, integer_one_node);
+  gimplify_assign (new_shift, shift_expr, &loop_seq);
+
+  /* other_var = shuffle (var, shift) */
+  nvptx_generate_vector_shuffle (loc, other_var, var, new_shift, &loop_seq);
+  /* new_var = var  OP other_var */
+  tree red_expr = fold_build2 (op, var_type, var, other_var);
+  gimplify_assign (new_var, red_expr, &loop_seq);
+
+  /* Mark the iterator variable as unified.  */
+  tree cond_var = make_ssa_name (integer_type_node);
+  tree uni_fn = nvptx_builtin_decl (NVPTX_BUILTIN_COND_UNI, true);
+  tree uni_expr = build_call_expr_loc (loc, uni_fn, 1, new_shift);
+  gimplify_assign (cond_var,  uni_expr, &loop_seq);
+
+  gcond *cond = gimple_build_cond (LE_EXPR, cond_var, integer_one_node,
+				   NULL_TREE, NULL_TREE);
+  gimple_seq_add_stmt (&loop_seq, cond);
+  
+  gsi_insert_seq_before (gsi, loop_seq, GSI_SAME_STMT);
+
+  /* Split the block just after the loop stmts.  */
+  edge post_edge = split_block (loop_bb, cond);
+  basic_block post_bb = post_edge->dest;
+  loop_bb = post_edge->src;
+  *gsi = gsi_for_stmt (gsi_stmt (*gsi));
+
+  /* Create the loop.  */
+  post_edge->flags ^= EDGE_TRUE_VALUE | EDGE_FALLTHRU;
+  edge loop_edge = make_edge (loop_bb, loop_bb, EDGE_FALSE_VALUE);
+  set_immediate_dominator (CDI_DOMINATORS, loop_bb, pre_bb);
+  set_immediate_dominator (CDI_DOMINATORS, post_bb, loop_bb);
+
+  gphi *shift_phi = create_phi_node (shift, loop_bb);
+  add_phi_arg (shift_phi, old_shift, pre_edge, loc);
+  add_phi_arg (shift_phi, new_shift, loop_edge, loc);
+
+  gphi *var_phi = create_phi_node (var, loop_bb);
+  add_phi_arg (var_phi, old_var, pre_edge, loc);
+  add_phi_arg (var_phi, new_var, loop_edge, loc);
+
+  loop *loop = alloc_loop ();
+  loop->header = loop_bb;
+  loop->latch = loop_bb;
+  add_loop (loop, loop_bb->loop_father);
+
+  return new_var;
+}
+
+/* Dummy reduction vars that have GOMP_MAP_FIRSTPRIVATE_POINTER data
+   mappings gets retyped to (void *).  Adjust the type of VAR to TYPE
+   as appropriate.  */
+
+static tree
+nvptx_adjust_reduction_type (tree var, tree type, gimple_seq *seq)
+{
+  if (TREE_TYPE (TREE_TYPE (var)) == type)
+    return var;
+
+  tree ptype = build_pointer_type (type);
+  tree t = make_ssa_name (ptype);
+  tree expr = fold_build1 (NOP_EXPR, ptype, var);
+  gimple_seq_add_stmt (seq, gimple_build_assign (t, expr));
+  return t;
+}
+
 /* NVPTX implementation of GOACC_REDUCTION_SETUP.  */
 
 static void
@@ -5602,7 +5790,11 @@ nvptx_goacc_reduction_setup (gcall *call)
       tree ref_to_res = gimple_call_arg (call, 1);
 
       if (!integer_zerop (ref_to_res))
-	var = build_simple_mem_ref (ref_to_res);
+	{
+	  ref_to_res = nvptx_adjust_reduction_type (ref_to_res, TREE_TYPE (var),
+						    &seq);
+	  var = build_simple_mem_ref (ref_to_res);
+	}
     }
   
   if (level == GOMP_DIM_WORKER)
@@ -5702,7 +5894,11 @@ nvptx_goacc_reduction_init (gcall *call)
 	    init = var;
 	}
 
-      gimplify_assign (lhs, init, &seq);
+      /* The LHS may be NULL if a reduction variable on a parallel
+	 construct is initialized to some constant inside the parallel
+	 region.  */
+      if (lhs)
+	gimplify_assign (lhs, init, &seq);
     }
 
   pop_gimplify_context (NULL);
@@ -5727,22 +5923,7 @@ nvptx_goacc_reduction_fini (gcall *call)
   push_gimplify_context (true);
 
   if (level == GOMP_DIM_VECTOR)
-    {
-      /* Emit binary shuffle tree.  TODO. Emit this as an actual loop,
-	 but that requires a method of emitting a unified jump at the
-	 gimple level.  */
-      for (int shfl = PTX_VECTOR_LENGTH / 2; shfl > 0; shfl = shfl >> 1)
-	{
-	  tree other_var = make_ssa_name (TREE_TYPE (var));
-	  nvptx_generate_vector_shuffle (gimple_location (call),
-					 other_var, var, shfl, &seq);
-
-	  r = make_ssa_name (TREE_TYPE (var));
-	  gimplify_assign (r, fold_build2 (op, TREE_TYPE (var),
-					   var, other_var), &seq);
-	  var = r;
-	}
-    }
+    r = nvptx_vector_reduction (gimple_location (call), &gsi, var, op);
   else
     {
       tree accum = NULL_TREE;
@@ -5760,7 +5941,11 @@ nvptx_goacc_reduction_fini (gcall *call)
       else if (integer_zerop (ref_to_res))
 	r = var;
       else
-	accum = ref_to_res;
+	{
+	  ref_to_res = nvptx_adjust_reduction_type (ref_to_res, TREE_TYPE (var),
+						    &seq);
+	  accum = ref_to_res;
+	}
 
       if (accum)
 	{
@@ -5809,7 +5994,11 @@ nvptx_goacc_reduction_teardown (gcall *call)
       tree ref_to_res = gimple_call_arg (call, 1);
 
       if (!integer_zerop (ref_to_res))
-	gimplify_assign (build_simple_mem_ref (ref_to_res), var, &seq);
+	{
+	  ref_to_res = nvptx_adjust_reduction_type (ref_to_res, TREE_TYPE (var),
+						    &seq);
+	  gimplify_assign (build_simple_mem_ref (ref_to_res), var, &seq);
+	}
     }
 
   if (lhs)
diff --git a/gcc/config/nvptx/nvptx.md b/gcc/config/nvptx/nvptx.md
index 2988f5dfa91..79c4c061841 100644
--- a/gcc/config/nvptx/nvptx.md
+++ b/gcc/config/nvptx/nvptx.md
@@ -600,6 +600,13 @@
   "%J0\\tbra.uni\\t%l1;"
   [(set_attr "predicable" "false")])
 
+(define_insn "cond_uni"
+  [(set (match_operand:SI 0 "nvptx_register_operand" "=R")
+          (unspec:SI [(match_operand:SI 1 "nvptx_nonmemory_operand" "R")]
+  		     UNSPEC_BR_UNIFIED))]
+  ""
+  "%.\\tmov%t0\\t%0, %1; // unified")
+
 (define_expand "cbranch<mode>4"
   [(set (pc)
 	(if_then_else (match_operator 0 "nvptx_comparison_operator"
diff --git a/gcc/omp-general.h b/gcc/omp-general.h
index 66f0a33c2e2..1a3a7cc728c 100644
--- a/gcc/omp-general.h
+++ b/gcc/omp-general.h
@@ -32,9 +32,10 @@ enum oacc_loop_flags {
   OLF_INDEPENDENT = 1u << 2,	/* Iterations are known independent.  */
   OLF_GANG_STATIC = 1u << 3,	/* Gang partitioning is static (has op). */
   OLF_TILE	= 1u << 4,	/* Tiled loop. */
-  
+  OLF_REDUCTION = 1u << 5,	/* Reduction loop.  */
+
   /* Explicitly specified loop axes.  */
-  OLF_DIM_BASE = 5,
+  OLF_DIM_BASE = 6,
   OLF_DIM_GANG   = 1u << (OLF_DIM_BASE + GOMP_DIM_GANG),
   OLF_DIM_WORKER = 1u << (OLF_DIM_BASE + GOMP_DIM_WORKER),
   OLF_DIM_VECTOR = 1u << (OLF_DIM_BASE + GOMP_DIM_VECTOR),
diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index c591231d8f1..792d338f0fd 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -4855,6 +4855,7 @@ lower_oacc_reductions (location_t loc, tree clauses, tree level, bool inner,
 	tree ref_to_res = NULL_TREE;
 	tree incoming, outgoing, v1, v2, v3;
 	bool is_private = false;
+	bool is_fpp = false;
 
 	enum tree_code rcode = OMP_CLAUSE_REDUCTION_CODE (c);
 	if (rcode == MINUS_EXPR)
@@ -4913,19 +4914,37 @@ lower_oacc_reductions (location_t loc, tree clauses, tree level, bool inner,
 		      is_private = true;
 		      goto do_lookup;
 		    }
+		  else if (OMP_CLAUSE_CODE (cls) == OMP_CLAUSE_MAP
+			   && (OMP_CLAUSE_MAP_KIND (cls)
+			       == GOMP_MAP_FIRSTPRIVATE_POINTER)
+			   && orig == OMP_CLAUSE_DECL (cls))
+		    {
+		      is_fpp = true;
+		      goto do_lookup;
+		    }
 	      }
 
 	  do_lookup:
 	    /* This is the outermost construct with this reduction,
 	       see if there's a mapping for it.  */
 	    if (gimple_code (outer->stmt) == GIMPLE_OMP_TARGET
-		&& maybe_lookup_field (orig, outer) && !is_private)
+		&& (maybe_lookup_field (orig, outer) || is_fpp) && !is_private)
 	      {
-		ref_to_res = build_receiver_ref (orig, false, outer);
-		if (omp_is_reference (orig))
-		  ref_to_res = build_simple_mem_ref (ref_to_res);
-
 		tree type = TREE_TYPE (var);
+
+		if (is_fpp)
+		  {
+		    tree x = create_tmp_var (type);
+		    gimplify_assign (x, lookup_decl (orig, outer), fork_seq);
+		    ref_to_res = x;
+		  }
+		else
+		  {
+		    ref_to_res = build_receiver_ref (orig, false, outer);
+		    if (omp_is_reference (orig))
+		      ref_to_res = build_simple_mem_ref (ref_to_res);
+		  }
+
 		if (POINTER_TYPE_P (type))
 		  type = TREE_TYPE (type);
 
@@ -5633,6 +5652,10 @@ lower_oacc_head_mark (location_t loc, tree ddvar, tree clauses,
 	  tag |= OLF_TILE;
 	  break;
 
+	case OMP_CLAUSE_REDUCTION:
+	  tag |= OLF_REDUCTION;
+	  break;
+
 	default:
 	  continue;
 	}
diff --git a/gcc/omp-offload.c b/gcc/omp-offload.c
index 0abf0283c9e..07ca759a7d8 100644
--- a/gcc/omp-offload.c
+++ b/gcc/omp-offload.c
@@ -1280,6 +1280,13 @@ oacc_loop_auto_partitions (oacc_loop *loop, unsigned outer_mask,
 	 non-innermost available level.  */
       unsigned this_mask = GOMP_DIM_MASK (GOMP_DIM_GANG);
 
+      /* Orphan reductions cannot have gang partitioning.  */
+      if ((loop->flags & OLF_REDUCTION)
+	  && oacc_get_fn_attrib (current_function_decl)
+	  && !lookup_attribute ("omp target entrypoint",
+				DECL_ATTRIBUTES (current_function_decl)))
+	this_mask = GOMP_DIM_MASK (GOMP_DIM_WORKER);
+
       /* Find the first outermost available partition. */
       while (this_mask <= outer_mask)
 	this_mask <<= 1;
@@ -1431,6 +1438,17 @@ default_goacc_reduction (gcall *call)
 
       if (!integer_zerop (ref_to_res))
 	{
+	  /* Dummy reduction vars that have GOMP_MAP_FIRSTPRIVATE_POINTER data
+	     mappings gets retyped to (void *).  Adjust the type of ref_to_res
+	     as appropriate.  */
+	  if (TREE_TYPE (TREE_TYPE (ref_to_res)) != TREE_TYPE (var))
+	    {
+	      tree ptype = build_pointer_type (TREE_TYPE (var));
+	      tree t = make_ssa_name (ptype);
+	      tree expr = fold_build1 (NOP_EXPR, ptype, ref_to_res);
+	      gimple_seq_add_stmt (&seq, gimple_build_assign (t, expr));
+	      ref_to_res = t;
+	    }
 	  tree dst = build_simple_mem_ref (ref_to_res);
 	  tree src = var;