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, 8 insertions, 0 deletions

diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 54b2954..4f3abb9 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -4190,6 +4190,14 @@ vect_loop_versioning (loop_vec_info loop_vinfo,
 			    prob * prob2, (prob * prob2).invert (),
 			    prob * prob2, (prob * prob2).invert (),
 			    true);
+
+      /* If the PHI nodes in the loop header were reallocated, we need to fix up
+	 our internally stashed copies of those.  */
+      if (loop_to_version == loop)
+	for (auto gsi = gsi_start_phis (loop->header);
+	     !gsi_end_p (gsi); gsi_next (&gsi))
+	  loop_vinfo->resync_stmt_addr (gsi.phi ());
+
       /* We will later insert second conditional so overall outcome of
 	 both is prob * prob2.  */
       edge true_e, false_e;