[nvptx] Rewrite nvptx_goacc_validate_dims to use predicate vars

The function nvptx_goacc_validate_dims has arguments decl and fn_level which
together describe different situations.

Introduce a predicate var for each situation, and use them, allowing to
understand what the function does in each situation without having to know the
way the situations are encoded in the args.

Build and reg-tested on x86_64 with nvptx accelerator.

2018-12-17  Tom de Vries  <tdevries@suse.de>

	* config/nvptx/nvptx.c (nvptx_goacc_validate_dims): Rewrite using
	predicate vars.

From-SVN: r267212

gcc/ChangeLog

+2018-12-17  Tom de Vries  <tdevries@suse.de>
+
+	* config/nvptx/nvptx.c (nvptx_goacc_validate_dims): Rewrite using
+	predicate vars.
+
 2018-12-17  Steve Ellcey  <sellcey@cavium.com>
 
 	* config/aarch64/aarch64-protos.h (aarch64_use_simple_return_insn_p):

gcc/config/nvptx/nvptx.c

@@ -5187,13 +5187,39 @@ static bool
 nvptx_goacc_validate_dims (tree decl, int dims[], int fn_level)
 {
   bool changed = false;
+  bool oacc_default_dims_p = false;
+  bool oacc_min_dims_p = false;
+  bool offload_region_p = false;
+  bool routine_p = false;
+  bool routine_seq_p = false;
+
+  if (decl == NULL_TREE)
+    {
+      if (fn_level == -1)
+	oacc_default_dims_p = true;
+      else if (fn_level == -2)
+	oacc_min_dims_p = true;
+      else
+	gcc_unreachable ();
+    }
+  else if (fn_level == -1)
+    offload_region_p = true;
+  else if (0 <= fn_level && fn_level <= GOMP_DIM_MAX)
+    {
+      routine_p = true;
+      routine_seq_p = fn_level == GOMP_DIM_MAX;
+    }
+  else
+    gcc_unreachable ();
 
   /* The vector size must be 32, unless this is a SEQ routine.  */
-  if (fn_level <= GOMP_DIM_VECTOR && fn_level >= -1
+  if ((offload_region_p || oacc_default_dims_p
+       || (routine_p && !routine_seq_p))
       && dims[GOMP_DIM_VECTOR] >= 0
       && dims[GOMP_DIM_VECTOR] != PTX_VECTOR_LENGTH)
     {
-      if (fn_level < 0 && dims[GOMP_DIM_VECTOR] >= 0)
+      if ((offload_region_p || oacc_default_dims_p)
+	  && dims[GOMP_DIM_VECTOR] >= 0)
 	warning_at (decl ? DECL_SOURCE_LOCATION (decl) : UNKNOWN_LOCATION, 0,
 		    dims[GOMP_DIM_VECTOR]
 		    ? G_("using vector_length (%d), ignoring %d")
@@ -5213,7 +5239,7 @@ nvptx_goacc_validate_dims (tree decl, int dims[], int fn_level)
       changed = true;
     }
 
-  if (!decl)
+  if (oacc_default_dims_p || oacc_min_dims_p)
     {
       dims[GOMP_DIM_VECTOR] = PTX_VECTOR_LENGTH;
       if (dims[GOMP_DIM_WORKER] < 0)