middle-end: Handle resized PHI nodes in loop_version()

While testing upcoming support for 64-bit location_t, I came across some
test failures on sparc (32-bit) that trigger when location_t is changed to
be 64-bit. The reason is that several call sites that make use of
loop_version() for performing loop optimizations assume that a gphi*
obtained prior to calling loop_version() will remain valid afterwards, but
this is not the case for a PHI that needs to be resized. It doesn't happen
usually, because PHI nodes usually have room for at least 4 arguments and
this is usually more than are needed, but this is not guaranteed.

Fix the affected callers by avoiding the assumption that a PHI node pointer
remains valid. For most cases, this is done by remembering instead the
gphi->result pointer, which contains a pointer back to the PHI node that is
kept up to date when the PHI is moved to a new address.

gcc/ChangeLog:

	* tree-parloops.cc (struct reduction_info): Store the result of the
	reduction PHI rather than the PHI itself.
	(reduction_info::reduc_phi): New member function.
	(reduction_hasher::equal): Adapt to the change in struct reduction_info.
	(reduction_phi): Likewise.
	(initialize_reductions): Likewise.
	(create_call_for_reduction_1): Likewise.
	(transform_to_exit_first_loop_alt): Likewise.
	(transform_to_exit_first_loop): Likewise.
	(build_new_reduction): Likewise.
	(set_reduc_phi_uids): Likewise.
	(try_create_reduction_list): Likewise.
	* tree-ssa-loop-split.cc (split_loop): Remember the PHI result
	variable so that the PHI can be found in case it is resized and move
	to a new address.
	* tree-vect-loop-manip.cc (vect_loop_versioning): After calling
	loop_version(), fix up stored PHI pointers in case they have
	changed.
	* tree-vectorizer.cc (vec_info::resync_stmt_addr): New function.
	* tree-vectorizer.h (vec_info::resync_stmt_addr): Declare.

1 files changed, 23 insertions, 0 deletions

diff --git a/gcc/tree-vectorizer.cc b/gcc/tree-vectorizer.cc
index 0bec280..92ecd88 100644
--- a/gcc/tree-vectorizer.cc
+++ b/gcc/tree-vectorizer.cc
@@ -540,6 +540,29 @@ vec_info::add_pattern_stmt (gimple *stmt, stmt_vec_info stmt_info)
   return res;
 }
 
+/* If STMT was previously associated with a stmt_vec_info and STMT now resides
+   at a different address than before (e.g., because STMT is a phi node that has
+   been resized), update the stored address to match the new one.  It is not
+   possible to use lookup_stmt () to perform this task, because that function
+   returns NULL if the stored stmt pointer does not match the one being looked
+   up.  */
+
+stmt_vec_info
+vec_info::resync_stmt_addr (gimple *stmt)
+{
+  unsigned int uid = gimple_uid (stmt);
+  if (uid > 0 && uid - 1 < stmt_vec_infos.length ())
+    {
+      stmt_vec_info res = stmt_vec_infos[uid - 1];
+      if (res && res->stmt)
+	{
+	  res->stmt = stmt;
+	  return res;
+	}
+    }
+  return nullptr;
+}
+
 /* If STMT has an associated stmt_vec_info, return that vec_info, otherwise
    return null.  It is safe to call this function on any statement, even if
    it might not be part of the vectorizable region.  */