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, 7 insertions, 0 deletions

diff --git a/gcc/tree-ssa-loop-split.cc b/gcc/tree-ssa-loop-split.cc
index 48d153d..a64066a 100644
--- a/gcc/tree-ssa-loop-split.cc
+++ b/gcc/tree-ssa-loop-split.cc
@@ -622,6 +622,7 @@ split_loop (class loop *loop1)
 	gphi *phi = find_or_create_guard_phi (loop1, guard_iv, &iv);
 	if (!phi)
 	  continue;
+	const tree phi_result = gimple_phi_result (phi);
 	gcond *guard_stmt = as_a<gcond *> (*gsi_last_bb (bbs[i]));
 	tree guard_init = PHI_ARG_DEF_FROM_EDGE (phi,
 						 loop_preheader_edge (loop1));
@@ -703,6 +704,12 @@ split_loop (class loop *loop1)
 					  profile_probability::very_likely (),
 					  true);
 	gcc_assert (loop2);
+
+	/* The phi address may have changed due to being resized in
+	   loop_version (), so reobtain it.  */
+	phi = as_a<gphi *> (SSA_NAME_DEF_STMT (phi_result));
+	gcc_checking_assert (gimple_bb (phi) == loop1->header);
+
 	/* Correct probability of edge  cond_bb->preheader_of_loop2.  */
 	single_pred_edge
 		(loop_preheader_edge (loop2)->src)->probability