Re: New post-LTO OpenACC pass

[Nathan Sidwell <nathan@acm.org>]

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On 09/21/15 16:39, Nathan Sidwell wrote:
> On 09/21/15 16:30, Cesar Philippidis wrote:
>> On 09/21/2015 09:30 AM, Nathan Sidwell wrote:
>>
>>> +const pass_data pass_data_oacc_transform =
>>> +{
>>> +  GIMPLE_PASS, /* type */
>>> +  "fold_oacc_transform", /* name */
>>
>> Want to rename the tree dump file to oacc_xforms like I'm did in the
>> attached patch? Regardless, I think we need to document this flag in
>> invoke.texi.
>
> Thanks for noticing the missing doc.  I'm not attached to any particular name.
> 'fold_oacc_transform' is rather generic, and a bit of  a mouthful.  Perhaps
> 'oacclower', 'oaccdevlower' or something (I  see there's 'lateomplower' for
> guidance)

this updated patch includes Cesar's doc patch.  Also change the name of the pass 
to 'oaccdevlow'.

nathan

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2015-09-22  Nathan Sidwell  <nathan@codesourcery.com>
	    Cesar Philippidis  <cesar@codesourcery.com>

	* omp-low.h (get_oacc_fn_attrib): Declare.
	* omp-low.c (get_oacc_fn_attrib): New.
	(oacc_xform_on_device): New.
	(execute_oacc_device_lower): New pass.
	(pass_data_oacc_device_lower): New.
	(pass_oacc_device_lower): New.
	(make_pass_oacc_device_lower): New.
	* tree-pass.h (make_pass_oacc_device_lower): Declare.
	* passes.def: Add pass_oacc_transform.
	* doc/invoke.texi: Document -fdump-tree-oaccdevlow.

Index: tree-pass.h
===================================================================
--- tree-pass.h	(revision 227968)
+++ tree-pass.h	(working copy)
@@ -406,6 +406,7 @@ extern gimple_opt_pass *make_pass_lower_
 extern gimple_opt_pass *make_pass_diagnose_omp_blocks (gcc::context *ctxt);
 extern gimple_opt_pass *make_pass_expand_omp (gcc::context *ctxt);
 extern gimple_opt_pass *make_pass_expand_omp_ssa (gcc::context *ctxt);
+extern gimple_opt_pass *make_pass_oacc_device_lower (gcc::context *ctxt);
 extern gimple_opt_pass *make_pass_object_sizes (gcc::context *ctxt);
 extern gimple_opt_pass *make_pass_strlen (gcc::context *ctxt);
 extern gimple_opt_pass *make_pass_fold_builtins (gcc::context *ctxt);
Index: passes.def
===================================================================
--- passes.def	(revision 227968)
+++ passes.def	(working copy)
@@ -148,6 +148,7 @@ along with GCC; see the file COPYING3.
   INSERT_PASSES_AFTER (all_passes)
   NEXT_PASS (pass_fixup_cfg);
   NEXT_PASS (pass_lower_eh_dispatch);
+  NEXT_PASS (pass_oacc_device_lower);
   NEXT_PASS (pass_all_optimizations);
   PUSH_INSERT_PASSES_WITHIN (pass_all_optimizations)
       NEXT_PASS (pass_remove_cgraph_callee_edges);
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 227968)
+++ doc/invoke.texi	(working copy)
@@ -7179,6 +7179,11 @@ is made by appending @file{.slp} to the
 Dump each function after Value Range Propagation (VRP).  The file name
 is made by appending @file{.vrp} to the source file name.
 
+@item oaccdevlow
+@opindex fdump-tree-oaccdevlow
+Dump each function after applying device-specific OpenACC transformations.
+The file name is made by appending @file{.oaccdevlow} to the source file name.
+
 @item all
 @opindex fdump-tree-all
 Enable all the available tree dumps with the flags provided in this option.
Index: omp-low.c
===================================================================
--- omp-low.c	(revision 227968)
+++ omp-low.c	(working copy)
@@ -8860,6 +8860,16 @@ expand_omp_atomic (struct omp_region *re
   expand_omp_atomic_mutex (load_bb, store_bb, addr, loaded_val, stored_val);
 }
 
+#define OACC_FN_ATTRIB "oacc function"
+
+/* Retrieve the oacc function attrib and return it.  Non-oacc
+   functions will return NULL.  */
+
+tree
+get_oacc_fn_attrib (tree fn)
+{
+  return lookup_attribute (OACC_FN_ATTRIB, DECL_ATTRIBUTES (fn));
+}
 
 /* Expand the GIMPLE_OMP_TARGET starting at REGION.  */
 
@@ -13909,4 +13919,131 @@ omp_finish_file (void)
     }
 }
 
+/* Transform an acc_on_device call.  OpenACC 2.0a requires this folded at
+   compile time for constant operands.  We always fold it.  In an
+   offloaded function we're never 'none'.  */
+
+static void
+oacc_xform_on_device (gimple *call)
+{
+  tree arg = gimple_call_arg (call, 0);
+  unsigned val = GOMP_DEVICE_HOST;
+	      
+#ifdef ACCEL_COMPILER
+  val = GOMP_DEVICE_NOT_HOST;
+#endif
+  tree result = build2 (EQ_EXPR, boolean_type_node, arg,
+			build_int_cst (integer_type_node, val));
+#ifdef ACCEL_COMPILER
+  {
+    tree dev  = build2 (EQ_EXPR, boolean_type_node, arg,
+			build_int_cst (integer_type_node,
+				       ACCEL_COMPILER_acc_device));
+    result = build2 (TRUTH_OR_EXPR, boolean_type_node, result, dev);
+  }
+#endif
+  result = fold_convert (integer_type_node, result);
+  tree lhs = gimple_call_lhs (call);
+  gimple_seq seq = NULL;
+
+  push_gimplify_context (true);
+  gimplify_assign (lhs, result, &seq);
+  pop_gimplify_context (NULL);
+
+  gimple_stmt_iterator gsi = gsi_for_stmt (call);
+  gsi_replace_with_seq (&gsi, seq, false);
+}
+
+/* Main entry point for oacc transformations which run on the device
+   compiler after LTO, so we know what the target device is at this
+   point (including the host fallback).  */
+
+static unsigned int
+execute_oacc_device_lower ()
+{
+  tree attrs = get_oacc_fn_attrib (current_function_decl);
+  
+  if (!attrs)
+    /* Not an offloaded function.  */
+    return 0;
+
+  basic_block bb;
+  FOR_ALL_BB_FN (bb, cfun)
+    for (gimple_stmt_iterator gsi = gsi_start_bb (bb);
+	 !gsi_end_p (gsi); gsi_next (&gsi))
+      {
+	gimple *stmt = gsi_stmt (gsi);
+	bool rescan = false;
+
+	if (!is_gimple_call (stmt))
+	  continue;
+
+	/* Rewind to allow rescan.  */
+	gsi_prev (&gsi);
+
+	gcall *call = as_a <gcall *> (stmt);
+	
+	if (gimple_call_builtin_p (call, BUILT_IN_ACC_ON_DEVICE))
+	  /* acc_on_device must be evaluated at compile time for
+	     constant arguments.  */
+	  {
+	    oacc_xform_on_device (call);
+	    rescan = true;
+	  }
+
+	if (gsi_end_p (gsi))
+	  /* We rewound past the beginning of the BB.  */
+	  gsi = gsi_start_bb (bb);
+
+	if (!rescan)
+	  /* Undo the rewind, so we don't get stuck infinitely.  */
+	  gsi_next (&gsi);
+      }
+
+  return 0;
+}
+
+namespace {
+
+const pass_data pass_data_oacc_device_lower =
+{
+  GIMPLE_PASS, /* type */
+  "oaccdevlow", /* name */
+  OPTGROUP_NONE, /* optinfo_flags */
+  TV_NONE, /* tv_id */
+  PROP_cfg, /* properties_required */
+  0 /* Possibly PROP_gimple_eomp.  */, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  TODO_update_ssa | TODO_cleanup_cfg, /* todo_flags_finish */
+};
+
+class pass_oacc_device_lower : public gimple_opt_pass
+{
+public:
+  pass_oacc_device_lower (gcc::context *ctxt)
+    : gimple_opt_pass (pass_data_oacc_device_lower, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  virtual unsigned int execute (function *)
+    {
+      bool gate = (flag_openacc != 0 && !seen_error ());
+
+      if (!gate)
+	return 0;
+
+      return execute_oacc_device_lower ();
+    }
+
+}; // class pass_oacc_transform
+
+} // anon namespace
+
+gimple_opt_pass *
+make_pass_oacc_device_lower (gcc::context *ctxt)
+{
+  return new pass_oacc_device_lower (ctxt);
+}
+
 #include "gt-omp-low.h"
Index: omp-low.h
===================================================================
--- omp-low.h	(revision 227968)
+++ omp-low.h	(working copy)
@@ -28,6 +28,7 @@ extern void free_omp_regions (void);
 extern tree omp_reduction_init (tree, tree);
 extern bool make_gimple_omp_edges (basic_block, struct omp_region **, int *);
 extern void omp_finish_file (void);
+extern tree get_oacc_fn_attrib (tree);
 
 extern GTY(()) vec<tree, va_gc> *offload_funcs;
 extern GTY(()) vec<tree, va_gc> *offload_vars;