[gimple] Move can_duplicate_bb_p to gimple_can_duplicate_bb_p

The function gimple_can_duplicate_bb_p currently always returns true.

The presence of can_duplicate_bb_p in tracer.c however suggests that
there are cases when bb's indeed cannot be duplicated.

Move the implementation of can_duplicate_bb_p to gimple_can_duplicate_bb_p.

Bootstrapped and reg-tested on x86_64-linux.

Build x86_64-linux with nvptx accelerator and tested libgomp.

No issues found.

As corner-case check, bootstrapped and reg-tested a patch that makes
gimple_can_duplicate_bb_p always return false, resulting in
PR97333 - "[gimple_can_duplicate_bb_p == false, tree-ssa-threadupdate]
ICE in duplicate_block, at cfghooks.c:1093".

gcc/ChangeLog:

2020-10-09  Tom de Vries  <tdevries@suse.de>

	* tracer.c (cached_can_duplicate_bb_p, analyze_bb): Use
	can_duplicate_block_p.
	(can_duplicate_insn_p, can_duplicate_bb_no_insn_iter_p)
	(can_duplicate_bb_p): Move and merge ...
	* tree-cfg.c (gimple_can_duplicate_bb_p): ... here.

1 files changed, 37 insertions, 1 deletions

diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 5caf3b6..002560d 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -6211,8 +6211,44 @@ gimple_split_block_before_cond_jump (basic_block bb)
 /* Return true if basic_block can be duplicated.  */
 
 static bool
-gimple_can_duplicate_bb_p (const_basic_block bb ATTRIBUTE_UNUSED)
+gimple_can_duplicate_bb_p (const_basic_block bb)
 {
+  gimple *last = last_stmt (CONST_CAST_BB (bb));
+
+  /* Do checks that can only fail for the last stmt, to minimize the work in the
+     stmt loop.  */
+  if (last) {
+    /* A transaction is a single entry multiple exit region.  It
+       must be duplicated in its entirety or not at all.  */
+    if (gimple_code (last) == GIMPLE_TRANSACTION)
+      return false;
+
+    /* An IFN_UNIQUE call must be duplicated as part of its group,
+       or not at all.  */
+    if (is_gimple_call (last)
+	&& gimple_call_internal_p (last)
+	&& gimple_call_internal_unique_p (last))
+      return false;
+  }
+
+  for (gimple_stmt_iterator gsi = gsi_start_bb (CONST_CAST_BB (bb));
+       !gsi_end_p (gsi); gsi_next (&gsi))
+    {
+      gimple *g = gsi_stmt (gsi);
+
+      /* An IFN_GOMP_SIMT_ENTER_ALLOC/IFN_GOMP_SIMT_EXIT call must be
+	 duplicated as part of its group, or not at all.
+	 The IFN_GOMP_SIMT_VOTE_ANY and IFN_GOMP_SIMT_XCHG_* are part of such a
+	 group, so the same holds there.  */
+      if (is_gimple_call (g)
+	  && (gimple_call_internal_p (g, IFN_GOMP_SIMT_ENTER_ALLOC)
+	      || gimple_call_internal_p (g, IFN_GOMP_SIMT_EXIT)
+	      || gimple_call_internal_p (g, IFN_GOMP_SIMT_VOTE_ANY)
+	      || gimple_call_internal_p (g, IFN_GOMP_SIMT_XCHG_BFLY)
+	      || gimple_call_internal_p (g, IFN_GOMP_SIMT_XCHG_IDX)))
+	return false;
+    }
+
   return true;
 }